Why don't voice radio communications use FM?

[Mxsmanic]

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio? I
realize there's substantial inertia in the installed base of AM
equipment, but surely one could allocate some new frequencies to FM
and use them in parallel for some years to ease the transition.

The reason I ask is that improper and misunderstood radio
communication is a leading cause of accidents, and so it seems that
anything that can make that communication clearer would greatly
improve safety. I can barely understand what I hear on the radio. It
is true that the communication is very standardized, making it easier
to guess what is being said, but the results are pretty unpleasant if
one guesses wrong.

On a related note, it has occurred to me that one could develop
voice-recognition systems that understand the speech of a pilot and
then repronounce what he says in an extremely standard synthetic
voice. This could also improve understanding, especially for
non-Anglophone pilots who speak with heavy accents. The same systems
could clean up the speech so that it is absolutely standard, with no
missing or added words. Of course, the issue here is that the system
would be stuck if it cannot recognize what is being said, or if a
completely non-standard utterance is made by the pilot. A natural
extension of this would be systems that recognize standard phrases in
one language and translate them to another, but that would be even
more dangerous if the system ever failed.

Still another idea is special training systems that listen to a
pilot's speech and transcribe it, and point out any problems with
understandability. Again, this would be most useful for
non-Anglophone pilots, but it would work for anyone. If a machine can
understand a pilot's speech clearly, then a human being should
certainly be able to understand it that much more easily.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Steven P. McNicoll[_1_]]

"Mxsmanic" > wrote in message
...
>
> Perhaps this is a naive question, but: Why don't voice radio
> communications for aviation use FM radio instead of AM radio?
>

Wouldn't that reduce the available frequencies?

[Peter R.]

Mxsmanic > wrote:

> The reason I ask is that improper and misunderstood radio
> communication is a leading cause of accidents,

A leading cause of accidents? Where did you get this statistic?

> but the results are pretty unpleasant if
> one guesses wrong.

Guess? If a pilot or controller is not able to comprehend the other side's
transmission, there is no guess. "Say again?" is the phrase of choice and
it is used all over the frequencies.



--
Peter

[James Robinson]

Mxsmanic > wrote:

> Perhaps this is a naive question, but: Why don't voice radio
> communications for aviation use FM radio instead of AM radio?

I understand it is because of a characteristic of FM called "capture
effect" that blanks out weaker transmissions when two radios transmit at
the same time. The listener would have no idea that a second, weaker
transmission was being made.

With AM, when two radios transmit on close frequencies, you either hear
both signals poorly, or you get squeal, which is the sum of the two
signals. This characteristic is considered important when you have elevated
transmitters that can be hundreds of miles away, like on aircraft.

[Larry Dighera]

On Sat, 02 Sep 2006 14:40:40 +0200, Mxsmanic >
wrote in >:

>Perhaps this is a naive question, but: Why don't voice radio
>communications for aviation use FM radio instead of AM radio?

I presume the reason stems from AM radio's introduction into aviation
after CW was used prior to and during WW-I. The cost of re-equipping
all aircraft with new radios is also not insignificant.

>I realize there's substantial inertia in the installed base of AM
>equipment, but surely one could allocate some new frequencies to FM
>and use them in parallel for some years to ease the transition.

AM frequencies are currently 25 kHz wide. FM would require more
bandwidth. Regardless, where would you place these newly allocated
frequencies?

>The reason I ask is that improper and misunderstood radio
>communication is a leading cause of accidents,

What is the source of that questionable statistic?

>and so it seems that anything that can make that communication clearer
>would greatly improve safety.

Hence the popularity of Active Noise Reduction headsets.

>I can barely understand what I hear on the radio.

Do you use an ANR headset?

>It is true that the communication is very standardized, making it easier
>to guess what is being said, but the results are pretty unpleasant if
>one guesses wrong.

Request 'say again' if in doubt.

>On a related note, it has occurred to me that one could develop
>voice-recognition systems that understand the speech of a pilot and
>then repronounce what he says in an extremely standard synthetic
>voice.

What would you estimate the cost of re-equipping all aircraft with
such a system might be?

>This could also improve understanding, especially for
>non-Anglophone pilots who speak with heavy accents. The same systems
>could clean up the speech so that it is absolutely standard, with no
>missing or added words. Of course, the issue here is that the system
>would be stuck if it cannot recognize what is being said, or if a
>completely non-standard utterance is made by the pilot. A natural
>extension of this would be systems that recognize standard phrases in
>one language and translate them to another, but that would be even
>more dangerous if the system ever failed.

Pilot: "Oh ****!"

Electronically rephrased: "Mayday!"

>Still another idea is special training systems that listen to a
>pilot's speech and transcribe it, and point out any problems with
>understandability. Again, this would be most useful for
>non-Anglophone pilots, but it would work for anyone. If a machine can
>understand a pilot's speech clearly, then a human being should
>certainly be able to understand it that much more easily.

I can understand you frustration with non-standard phraseology and
foreign accents, but given the current state of the art, such a voice
recognition/synthetic voice system as you suggest would probably be
unworkable not to mention costly and short lived. I would expect to
see data-link equipment (ACARS* or more likely ATN** or NEXCOM***)
available for GA aircraft soon.

* http://en.wikipedia.org/wiki/ACARS
** http://www.tc.faa.gov/act300/act350/
*** http://www.faa.gov/nextgen/nexcom/Publib/aboutnc2.htm

[Emily[_1_]]

Mxsmanic wrote:

> The reason I ask is that improper and misunderstood radio
> communication is a leading cause of accidents

Really? Can you cite some statistics? I'd be very interested in
reading them.

[RST Engineering]

Yeah, Steve, it would. But I think we might be able to swap (on a long term
swap basis) the VHF com band for stuff up between 600 and 900 MHz. that have
very limited usage. Not only could we get way more bandwidth, but the
antenna size is cut by a factor of 6 or so.

Jim


"Steven P. McNicoll" > wrote in message
nk.net...
>
> "Mxsmanic" > wrote in message
> ...
>>
>> Perhaps this is a naive question, but: Why don't voice radio
>> communications for aviation use FM radio instead of AM radio?
>>
>
> Wouldn't that reduce the available frequencies?
>

[John Gaquin]

"Mxsmanic" > wrote in message
>
> ....that improper and misunderstood radio
> communication is a leading cause of accidents,

Cite, please.

>... I can barely understand what I hear on the radio.

I suspect the reasons for this relate more to the environmental effects and
quality of the speakers, etc., than to the nature of AM transmissions.

[John Gaquin]

"James Robinson" > wrote in message

> With AM, when two radios transmit on close frequencies, you either hear
> both signals poorly, or you get squeal, which is the sum of the two
> signals. This characteristic is considered important when you have
> elevated
> transmitters that can be hundreds of miles away, like on aircraft.

Sounds plausible. Marine radios also operate in the VHF band, but are FM.
They are also almost always at or very close to sea level.

[RST Engineering]

Red herring, again. AM radio does the same suppression effect if the
signals are widely differing in power (google "AGC" or "AVC" for an
explanation). The odds of two signals being absolutely equal in time is
close to zero. True, they can start simultaneously, but the ending time is
generally measured in multiseconds. One side or the other always gets the
tag end of one conversation or the other and can figure out that a second
station is trying to get a message across.

The squeal when two nearly equal power signals is not the sum of the
frequencies, it is the difference.


Jim



"James Robinson" > wrote in message
. ..
> Mxsmanic > wrote:
>
>> Perhaps this is a naive question, but: Why don't voice radio
>> communications for aviation use FM radio instead of AM radio?
>
> I understand it is because of a characteristic of FM called "capture
> effect" that blanks out weaker transmissions when two radios transmit at
> the same time. The listener would have no idea that a second, weaker
> transmission was being made.
>
> With AM, when two radios transmit on close frequencies, you either hear
> both signals poorly, or you get squeal, which is the sum of the two
> signals. This characteristic is considered important when you have
> elevated
> transmitters that can be hundreds of miles away, like on aircraft.

[RST Engineering]

That's just not true. For a given voice signal, I can squeeze the same
amount of fidelity into an FM channel that I can into an AM channel.

The current actual transmitted bandwidth of a VHF AM signal is about 4 kHz..
Standard deviation on a VHF FM signal is 3.5 kHz.. Bessel and Armstrong to
the rescue once more {;-)

BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going to
be a challenge for us AMers to meet.

Jim




"Larry Dighera" > wrote in message
...


> AM frequencies are currently 25 kHz wide. FM would require more
> bandwidth. Regardless, where would you place these newly allocated
> frequencies?

[Larry Dighera]

>"Larry Dighera" > wrote in message
...

>> AM frequencies are currently 25 kHz wide. FM would require more
>> bandwidth. Regardless, where would you place these newly allocated
>> frequencies?
>

On Sat, 2 Sep 2006 09:10:19 -0700, "RST Engineering"
> wrote in
>:

>That's just not true. For a given voice signal, I can squeeze the same
>amount of fidelity into an FM channel that I can into an AM channel.

That's the first time I've heard that.

>The current actual transmitted bandwidth of a VHF AM signal is about 4 kHz..

Does that mean the highest audio frequency transmitted it 2kHz?

>Standard deviation on a VHF FM signal is 3.5 kHz.. Bessel and Armstrong to
>the rescue once more {;-)
>
>BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going to
>be a challenge for us AMers to meet.
>

And, I suspect, it would be completely impossible for FM to fit within
8.3 kHz channel spacing with the same fidelity?

[Bob Noel]

In article >,
"RST Engineering" > wrote:

> BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going to
> be a challenge for us AMers to meet.

huh? Putting FM into 8.33 kHz spacing? or did you mean something else?

--
Bob Noel
Looking for a sig the
lawyers will hate

[Ron Natalie]

James Robinson wrote:
> Mxsmanic > wrote:
>
>> Perhaps this is a naive question, but: Why don't voice radio
>> communications for aviation use FM radio instead of AM radio?
>
> I understand it is because of a characteristic of FM called "capture
> effect" that blanks out weaker transmissions when two radios transmit at
> the same time. The listener would have no idea that a second, weaker
> transmission was being made.
>
No actually, it's just historical. Early av radio used AM, and for that
reason we still do.

[RST Engineering]

>
>>That's just not true. For a given voice signal, I can squeeze the same
>>amount of fidelity into an FM channel that I can into an AM channel.
>
> That's the first time I've heard that.

The first time I heard it was when VHF FM at 2 meters became popular in the
early 1960s. The first time I had it explained using Bessel functions was
as a first year graduate student in the late 1960s. The first time I had a
chance to design with it was my first FCC type acceptance gauntlet in the
mid 1970s.

Take a look at a ham 2 meter rig sometime. Channels are 5 kHz. wide.


>
>>The current actual transmitted bandwidth of a VHF AM signal is about 4
>>kHz..
>
> Does that mean the highest audio frequency transmitted it 2kHz?

No, sorry, I should have been absolutely technically precise. The current
actual transmitted bandwidth of a VHF AM signal is plus/minus 4 kHz.. In
practice, with symmetric modulation ("good" AM or FM) you generally give the
bandwidth as the distance from carrier to one sideband and not sideband to
sideband.

The highest audio frequency that we try to achieve is about 3 to 3.5 kHz,
with rapid rolloff above 2.5 kHz. -- generally 12 to 18 dB/octave cornered
on 2.5 kHz.. Yes, there will be some higher order stuff leaking through;
the idea is to contain as much of it as you can in the filter before it hits
the modulator.

>
>>Standard deviation on a VHF FM signal is 3.5 kHz.. Bessel and Armstrong
>>to
>>the rescue once more {;-)
>>
>>BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going
>>to
>>be a challenge for us AMers to meet.
>>
>
> And, I suspect, it would be completely impossible for FM to fit within
> 8.3 kHz channel spacing with the same fidelity?

Easier for FM than AM, but it is a moot point. FM will PROBABLY never
happen on the VHF COM band.

Jim

[Steven P. McNicoll[_1_]]

"Ron Natalie" > wrote in message
m...
>
> No actually, it's just historical. Early av radio used AM, and for that
> reason we still do.
>

Didn't all early radio use AM?

[[email protected]]

On Sat, 2 Sep 2006 12:02:26 -0400, "John Gaquin"
> wrote:

>
>"Mxsmanic" > wrote in message
>>
>> ....that improper and misunderstood radio
>> communication is a leading cause of accidents,
>
>Cite, please.
>
>>... I can barely understand what I hear on the radio.
>
>I suspect the reasons for this relate more to the environmental effects and
>quality of the speakers, etc., than to the nature of AM transmissions.
>

The previous comment re capture effect of FM is valid. i.e. the
strongest signal wins. This is desireable for broadcast radio but not
aviation.

With FM the signal remains much clearer until the point where it
suddenly becomes unreadable when itl becomes weak.

With AM is that readability gradually reduces as the signal gets
weaker. If you open the squelch you can often still read AM when FM
would be unreadable.

The audio bandwidth for acceptable communication is 3KHz. When
modulating an AM transmitter you have two sidebands. One up to -3KHz
the other up to +3KHz so transmitted bandwidth is 6KHz.

With an FM transmitter the bandwidth will still be 6KHz plus the
deviation of the system. In addition the sidebands theoretically
extend to infinity but they become rapidly weaker.

To get the best signal to noise ratio with FM you need higher
deviation. If you try increase the number of FM frequencies you need
to reduce the deviation. That in turn would reduce its effectivness.

As for the original comments I would suggest there's something wrong
if AM is not clear.

Could be poor hearing, inadequate headset, turning up the volume
causing overload of either headset or receiver audio. Ignition or
alternator interference distorting the received signal, poor
transmitter, poor microphone, poor microphone technique.
Sorry but the problem is NOT AM!

[Peter Dohm]

"Larry Dighera" > wrote in message
...
>
> >"Larry Dighera" > wrote in message
> ...
>
> >> AM frequencies are currently 25 kHz wide. FM would require more
> >> bandwidth. Regardless, where would you place these newly allocated
> >> frequencies?
> >
>
> On Sat, 2 Sep 2006 09:10:19 -0700, "RST Engineering"
> > wrote in
> >:
>
> >That's just not true. For a given voice signal, I can squeeze the same
> >amount of fidelity into an FM channel that I can into an AM channel.
>
> That's the first time I've heard that.
>
> >The current actual transmitted bandwidth of a VHF AM signal is about 4
kHz..
>
> Does that mean the highest audio frequency transmitted it 2kHz?
>
> >Standard deviation on a VHF FM signal is 3.5 kHz.. Bessel and Armstrong
to
> >the rescue once more {;-)
> >
> >BTW, the current European channel spacing is 8.3 kHz.. Now THAT's going
to
> >be a challenge for us AMers to meet.
> >
I believe they were just implementing that when I left avionics work 20
years ago. The main reason for the relatively wide spacing was poor
frequency stability. The real problems with any changeover would/will be
the large amount of existing infrastructure in place and the need for
radically "better" adjacent channel rejection. And you don't dare to
"improve" the adjacent frequency rejection of the receivers that much untill
you are really sure that the transmitters in service can meet the new
standard ... and so forth ...
>
> And, I suspect, it would be completely impossible for FM to fit within
> 8.3 kHz channel spacing with the same fidelity?
>
Wouldn't be much of a problem, IIRC the hams have been doing it forever. I
just don't know of and good reason to choose one modulation scheme over the
other, and certainly not to change from one to the other!

[Mxsmanic]

Steven P. McNicoll writes:

> Wouldn't that reduce the available frequencies?

For a given audio bandwidth, FM tends to require somewhat more radio
bandwidth, as I recall, but the audio bandwidth of aviation radio is
already so limited that I don't think this would be an issue. The
gain in clarity would outweigh any loss of audio fidelity, assuming
that the same channel widths were used.

If frequencies were reallocated (instead of allocating new ones), that
would be different. That would also obsolete older equipment much
more quickly, which might not be acceptable. But there must be some
space somewhere that could be added to the frequencies, or perhaps
some band so rarely used that it could be reassigned.

--
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[Jim Logajan]

Mxsmanic > wrote:
> Perhaps this is a naive question, but: Why don't voice radio
> communications for aviation use FM radio instead of AM radio? I
> realize there's substantial inertia in the installed base of AM
> equipment, but surely one could allocate some new frequencies to FM
> and use them in parallel for some years to ease the transition.

If one were to mandate a replacement technology, it would be far far more
effective to use the packet-based mechanisms that digital cellular phone
technology and 802.11 wireless Ethernet (aka WiFi) rely on. Both these
technologies turn over the job of transmission collision resolution to
chip logic and take humans out of the loop. And it is possible to put
audio over WiFi using Voice over IP (VoIP) technology.

Such a system would be incredibly flexible. If one had, say, ten planes
in the air and they all started to talk to ATC at once, a packet-based
system would make it possible to do any of the following:

1) Clearly deliver only one of the voice signals to the controller and
provide a visual display that indicated 9 other planes had attempted to
speak also. It could even provide audio or visual feedback to the other 9
pilots that their transmissions were not delivered - or it could
automatically sequence the delivery of the transmissions to the
controller if the transmissions were not too lengthy.

2) If multiple controllers were available, the audio from several of the
planes could be routed to multiple controllers with no impact on audio
fidelity as far as the controllers or pilots are concerned.

3) Once you go packetized audio, you can put all sorts of useful stuff in
the packets for presentation to the other end - such as aircraft number,
the location and velocity vector from the aircraft's GPS or
altimeter/DG/airspeed indicator, and so on. A pilot could key the mike
and make a request without needing to ID themselves or their position -
that information would be extracted from the audio packet's header and
automatically presented on either a simple display to the controller or
mapped to a fancy map display.

The technical issues have been pretty much solved and commoditized in
both the WiFi VoIP and digital cellular realms. It is my humble opinion
that the radio technology currently being used for aviation
communications is now less reliable and useful than even that used in
home WiFi networks.

Maybe someday the FAA and/or ICAO will consider replacing analog radios
with a more capable digital system....

[Mxsmanic]

Peter R. writes:

> A leading cause of accidents? Where did you get this statistic?

From the NTSB and several books on the subject.

> Guess? If a pilot or controller is not able to comprehend the other side's
> transmission, there is no guess. "Say again?" is the phrase of choice and
> it is used all over the frequencies.

It's routine in linguistics to unconsciously guess. A person
listening to familiar sounds in a familiar context will "fill in the
blanks" for any sounds that cannot be unambiguously distinguished, and
he will do this without thinking. If he guesses wrong, trouble can
result, and accidents have happened in aviation for this reason (the
most famous probably being the one at Tenerife).

--
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[Mxsmanic]

James Robinson writes:

> I understand it is because of a characteristic of FM called "capture
> effect" that blanks out weaker transmissions when two radios transmit at
> the same time. The listener would have no idea that a second, weaker
> transmission was being made.

It might be possible to use digital FM and employ anticollision
methods such as those used in other media (networks and so on).
Digital FM would be completely noise free. GSM cellphone technology
already works this way. Also, spread frequency methods such as those
used by GPS can help resolve collision issues, although in aviation
voice communications you really want only one channel speaking at a
time (but I'm sure this could easily be worked out).

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[Mxsmanic]

Ron Natalie writes:

> No actually, it's just historical. Early av radio used AM, and for that
> reason we still do.

If that were the only reason, nothing would ever change in aviation.
There must be some reason beyond that. Concerns over safety come to
mind immediately, and ecnonomic issues follow; but in the case of
voice communications, they are so bad already that one can argue that
a newer technology would increase safety more than enough to justify
the initial risk of a new system.

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[Mxsmanic]

Larry Dighera writes:

> Hence the popularity of Active Noise Reduction headsets.

Then why not apply the same logic to the radio channel itself, and
reduce its noise as well.

> Do you use an ANR headset?

No. The source of the noise is not anything around me, it's coming
from the channel itself.

> Request 'say again' if in doubt.

Most people guess without realizing it, so they cannot do that.

> What would you estimate the cost of re-equipping all aircraft with
> such a system might be?

They don't all have to be reequipped at once, any more than everyone
must have a glass cockpit.

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[Mxsmanic]

Emily writes:

> Really? Can you cite some statistics? I'd be very interested in
> reading them.

Just look through accident and incident reports. Radio communication
is one of the weak links in the aviation safety chain.

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[RST Engineering]

You recall incorrectly.

Jim


"Mxsmanic" > wrote in message
...
> Steven P. McNicoll writes:
>
>> Wouldn't that reduce the available frequencies?
>
> For a given audio bandwidth, FM tends to require somewhat more radio
> bandwidth, as I recall,

[Stefan]

Mxsmanic schrieb:

> Just look through accident and incident reports. Radio communication
> is one of the weak links in the aviation safety chain.

But not because of bad sound quality, but because pilots under pressure
tend to hear what they expect to hear. (A phenomene which does not only
occur with pilots BTW.) These accidents would have happened with hifi
qualitiy radio, too.

Stefan

[Mxsmanic]

RST Engineering writes:

> You recall incorrectly.

Perhaps. Theoretically it should require exactly the same bandwidth,
but I seem to recall reading that typical implementations used more
bandwidth. In any case, you don't need much for voice communication.
The advantage of FM would be the reduction of noise. Digital over FM
would be still better.

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[Mxsmanic]

Stefan writes:

> But not because of bad sound quality, but because pilots under pressure
> tend to hear what they expect to hear.

The worse the sound quality is, the more pilots must "fill in the
blanks," and the more likely they are to hear what they want to hear.

If you hear something that could be "five" or "nine," you're much more
likely to choose the number that suits you than you are if you hear
something that is unambiguously one of the two.

--
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[Mxsmanic]

Jim Logajan writes:

<details snipped>

> Maybe someday the FAA and/or ICAO will consider replacing analog radios
> with a more capable digital system....

All very interesting, but one of the criteria that any new system
would have to satisfy is that it would have to work in parallel with
the existing system. Adding features to the new system that are not
available in the old system would create dangerous differences between
the two. Seeing fancy displays in the ATC or tower for the lucky
digital users won't help deal with traffic from old AM users, and it
might even confuse things enough to cause problems.

A highly advanced solution would require replacing everything at once,
which isn't going to happen. A simpler solution that just provides
better quality audio could coexist with older systems without a
problem.

--
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[Kyle Boatright]

"Mxsmanic" > wrote in message
...
> Emily writes:
>
>> Really? Can you cite some statistics? I'd be very interested in
>> reading them.
>
> Just look through accident and incident reports. Radio communication
> is one of the weak links in the aviation safety chain.

If you're going to make the claim, point to a viable source of information.
Without providing data, it is just your opinion.

I have read thousands of NTSB reports and don't remember a single one where
the technological limitation inherent in AM radio was a significant cause of
the accident.

> --
> Transpose mxsmanic and gmail to reach me by e-mail.

KB

[Stefan]

Mxsmanic schrieb:

> If you hear something that could be "five" or "nine," you're much more
> likely to choose the number that suits you than you are if you hear
> something that is unambiguously one of the two.

That's exactly the reason why it's "niner".

Stefan

[Peter R.]

Mxsmanic > wrote:

> The worse the sound quality is, the more pilots must "fill in the
> blanks," and the more likely they are to hear what they want to hear.
>
> If you hear something that could be "five" or "nine," you're much more
> likely to choose the number that suits you than you are if you hear
> something that is unambiguously one of the two.

You are not a pilot, it seems. These claims of yours read as if they are
opinion based on an outsider's perspective, not one who actually has some
hours of aviation radio experience.

With regards to aviation communication, "niner" is the proper phonetic
pronunciation of nine and "fife" is the proper pronunciation of five,
although admittedly "fife" is not as widely used as it should be.

--
Peter

[Peter R.]

Mxsmanic > wrote:

> From the NTSB and several books on the subject.

Have a name of one of these books that claims that aviation communication
is the leading cause of aviation accidents?


> It's routine in linguistics to unconsciously guess. A person
> listening to familiar sounds in a familiar context will "fill in the
> blanks" for any sounds that cannot be unambiguously distinguished, and
> he will do this without thinking.

You imply that this is a very common occurrence. Sorry, but I am unable to
accept your premise without some evidence to back up this claim.

> If he guesses wrong, trouble can
> result, and accidents have happened in aviation for this reason (the
> most famous probably being the one at Tenerife).

My understanding of the accident at Tenerife is that it had more to do with
a fateful heterodyne and a captain who was asserting his own way, rather
than misunderstood communications.


--
Peter

[Vaughn Simon]

"Mxsmanic" > wrote in message
...
> Ron Natalie writes:
>
>> No actually, it's just historical. Early av radio used AM, and for that
>> reason we still do.
>
> If that were the only reason, nothing would ever change in aviation.


Actually, not much does change in aviation compared with other fields of
human endeavor . But changing to FM would require a new radio to be
simultaneously installed in every cockpit in the world. The only way to
accomplish that would be for every plane with a new radio to transmit in
"parallel" (as someone already suggested) for a period of years on both the new
mode and the old mode. What are the chances of AOPA allowing that to happen?

That said, I would really like to see it. It would be great to have enough
frequencies to go around so that you would not have to be constantly mentally
filtering out the transmissions from adjacent uncontrolled airports.

Vaughn

[Mxsmanic]

Peter R. writes:

> My understanding of the accident at Tenerife is that it had more to do with
> a fateful heterodyne and a captain who was asserting his own way, rather
> than misunderstood communications.

Some of the words on the cockpit recording are impossible to
understand even today. That's pretty strong evidence that
misunderstood communications had an important role in this accident.
In fact, there are several instances of misunderstood radio
communication involved.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Stefan writes:

> That's exactly the reason why it's "niner".

They still sound the same if the channel is noisy enough.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Peter R. writes:

> With regards to aviation communication, "niner" is the proper phonetic
> pronunciation of nine and "fife" is the proper pronunciation of five,
> although admittedly "fife" is not as widely used as it should be.

They still sound very much the same.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Thomas Borchert]

Mxsmanic,

> From the NTSB and several books on the subject.
>

Like which?

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

> > Do you use an ANR headset?
>
> No. The source of the noise is not anything around me, it's coming
> from the channel itself.
>

ANR headsets enhance speech as well as reducing noise.

--
Thomas Borchert (EDDH)

[Steve Foley[_2_]]

"Mxsmanic" > wrote in message
...

> Some of the words on the cockpit recording are impossible to
> understand even today.

Those are not transmitted AM or FM. They are hard wired. This seems to
defeat your point.


> In fact, there are several instances of misunderstood radio
> communication involved.

You keep mkaing vague references to these instances. Can you cite even one?

[Larry Dighera]

On Sat, 02 Sep 2006 16:58:12 GMT, "Steven P. McNicoll"
> wrote in
et>:

>
>"Ron Natalie" > wrote in message
m...
>>
>> No actually, it's just historical. Early av radio used AM, and for that
>> reason we still do.
>>
>
>Didn't all early radio use AM?
>

Early radio, including aviation, used Continuous Wave (CW) modulation
and Morris Code.

Edwin Armstrong patented Frequency Modulation (FM) in 1933.*


* http://en.wikipedia.org/wiki/Edwin_Howard_Armstrong

[Jim Logajan]

Mxsmanic > wrote:
> Jim Logajan writes:
>
> <details snipped>
>
>> Maybe someday the FAA and/or ICAO will consider replacing analog radios
>> with a more capable digital system....
>
> All very interesting, but one of the criteria that any new system
> would have to satisfy is that it would have to work in parallel with
> the existing system. Adding features to the new system that are not
> available in the old system would create dangerous differences between
> the two. Seeing fancy displays in the ATC or tower for the lucky
> digital users won't help deal with traffic from old AM users, and it
> might even confuse things enough to cause problems.
>
> A highly advanced solution would require replacing everything at once,
> which isn't going to happen. A simpler solution that just provides
> better quality audio could coexist with older systems without a
> problem.

Analog AM and FM are fundamentally incompatible with each other. Analog AM
and digital encoding over spread-spectrum are fundamentally incompatible
with each other. You asked why AM is being used and not FM and all I'm
pointing out is that if you are willing to consider any new system that is
incompatible with an older system (like FM replacing AM), you may as well
do it with something more advanced and capable, like digital packets over
spread spectrum (which could be considered a relative to FM). One does
_not_ need to implement any of the fancier capabilities that I mentioned. I
stated them only as what could be easily done once the capability is in
place.

Analog cell phones are being replaced with digital cell phones, so I fully
expect the same co-existence can be done with a changeover from analog
aviation radio to digital radio. There would be no need to replace
everything at once and I'm not sure why you think that would need to be the
case.

[Jim Logajan]

"Vaughn Simon" > wrote:
> But changing to FM would require a new radio to be
> simultaneously installed in every cockpit in the world. The only way
> to accomplish that would be for every plane with a new radio to
> transmit in "parallel" (as someone already suggested) for a period of
> years on both the new mode and the old mode.

That need not be the case, as evidenced by dual-mode cell phones that allow
access to analog and digital cell sites, though not both at the same time.
Newer radios could certainly be made capable of either mode and a future
cutoff date X years in the future could be set for required switchover when
older model radios would be required to be replaced. This would certainly
ease the transition woes.

> Actually, not much does change in aviation compared with other fields of
> human endeavor.

It does seem that way. Unfortunately I don't think there is anyone in the
FAA or even the avionics industry who is both sufficiently knowledgeable
about recent advances in communications and has the clout and vision to
push for a radical improvement of aviation communication.

[Larry Dighera]

On Sat, 02 Sep 2006 19:51:30 +0200, Mxsmanic >
wrote in >:

>Larry Dighera writes:
>
>> Hence the popularity of Active Noise Reduction headsets.
>
>Then why not apply the same logic to the radio channel itself, and
>reduce its noise as well.

I would guess that noise-blanker and noise-limiting circuits are
incorporated in the current radio designs.

>> Do you use an ANR headset?
>
>No. The source of the noise is not anything around me, it's coming
>from the channel itself.

Other than the occasional heterodyne squeal that occurs in the
receiver when two transmitters are transmitting on the same frequency
simultaneously, there shouldn't be any other noise. Ignition noise
should be suppressed by Faraday shielding, and generator/alternator
noise should be bypassed to ground.

What is the nature of the noise you are hearing? Can you describe it?
Is it a hum, pulses, growling, squealing, what?

>> What would you estimate the cost of re-equipping all aircraft with
>> such a system might be?
>
>They don't all have to be reequipped at once, any more than everyone
>must have a glass cockpit.

Regardless of when it occurs, there will ultimately be an additional
cost.

And to expect the old (current) communications system to remain
operational while the new system you are proposing is operating
concurrently won't be feasible if they use the same frequencies. If
an new alternate frequency band is used for the new communications
system you are proposing, it could work. But getting the FCC to
allocate additional frequency spectrum will probably be opposed,
because the frequency spectrum is a finite resource, and there are
many more services desiring to use it than there is bandwidth
available.

You really should read the information at some of the links I provided
to get an idea of what has been tried, and what is on the FAA's
horizon regarding aviation communications. This topic has been very
thoroughly researched by government personnel and it's unlikely that
you will hit upon a superior system to what the professionals have
examined.

[Larry Dighera]

On Sat, 2 Sep 2006 14:39:42 -0400, "Peter R." >
wrote in >:

>You are not a pilot, it seems. These claims of yours read as if they are
>opinion based on an outsider's perspective, not one who actually has some
>hours of aviation radio experience.

It would seem, that Mxsmanic may be one of the "Pilots for 9/11
Truth."

[Larry Dighera]

On Sat, 02 Sep 2006 21:06:47 -0000, Jim Logajan >
wrote in >:

>Analog cell phones are being replaced with digital cell phones, so I fully
>expect the same co-existence can be done with a changeover from analog
>aviation radio to digital radio.

They operate on different frequency bands, so that is not a good
analogy unless you can get the FCC to commit to allocating frequency
spectrum for aviation use.

>There would be no need to replace everything at once and I'm not sure
>why you think that would need to be the case.

Because it is unlikely the FCC will agree to allocate additional
frequency spectrum for the proposed new communications system.

[Jim Logajan]

Larry Dighera > wrote:
> I would expect to
> see data-link equipment (ACARS* or more likely ATN** or NEXCOM***)
> available for GA aircraft soon.
>
> * http://en.wikipedia.org/wiki/ACARS
> ** http://www.tc.faa.gov/act300/act350/
> *** http://www.faa.gov/nextgen/nexcom/Publib/aboutnc2.htm

Ah - thanks for the links. The last one states:

"Through the RTCA forum and the FAA's Investment Analysis process, the Time
Division Multiple Access (TDMA) system was selected for implementation. The
TDMA system will use multi channels to operate on one 25 kHz frequency
assignment. The system will utilize Differential (D8PSK) Phase Shift Keying
(D8PSK) and will require a 4.8 KB VOCODER for voice operation. While
current planning calls for operating the system in a 2 -Voice/2 -Data
configuration, other combinations could also be used. Standards for the
system, termed VHF Digital Link Mode Three or VDL-3, are close to
completion and are expected to be validated. In the fully operational
state, the system will accommodate both voice and data."

That would definitely be a great solution, but that page was last updated
January 4, 2000. Do you or anyone else know if any further progress been
made or have the efforts died? (The links I could find all seemed to dead-
end.)

[Mxsmanic]

Vaughn Simon writes:

> Actually, not much does change in aviation compared with other fields of
> human endeavor.

I don't think that is necessarily a bad thing. It does worry me that
the things that change in aviation are things that I'd rather see
stable. I have my doubts about fly-by-wire systems or glass cockpits,
which seem to be increasingly designed for the convenience of
programmers who grew up with Windows rather than for the convenience
of pilots.

> But changing to FM would require a new radio to be
> simultaneously installed in every cockpit in the world. The only way to
> accomplish that would be for every plane with a new radio to transmit in
> "parallel" (as someone already suggested) for a period of years on both the new
> mode and the old mode. What are the chances of AOPA allowing that to happen?

I don't see why it would be so objectionable. It isn't even necessary
that the AM be phased out. The FM would simply be available to those
who wish to use it, for the added clarity it provides.

When multiple frequencies are available for the same communication,
you could allocate some to FM and some to AM. Initially all would be
AM. Gradually they'd be shifted to FM as time passes, with plenty of
documentation. Eventually only one AM frequency would be left, which
could be kept active indefinitely.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Jim Logajan writes:

> Analog AM and FM are fundamentally incompatible with each other.

Not if they are on different frequencies.

> Analog AM and digital encoding over spread-spectrum are fundamentally
> incompatible with each other.

Analog AM is used for digital spread-spectrum encoding. AM is the
modulation. Digital is the encoding. Spread-spectrum is just a
frequency and bandwidth assignment.

> You asked why AM is being used and not FM and all I'm
> pointing out is that if you are willing to consider any new system that is
> incompatible with an older system (like FM replacing AM), you may as well
> do it with something more advanced and capable, like digital packets over
> spread spectrum (which could be considered a relative to FM).

Switching from AM to FM doesn't involve incompatibilities. You can
run both in parallel indefinitely, providing identical services (just
as some commercial radio stations have broadcasts on both AM and FM
simultaneously). Introducing FM doesn't obsolete any of the AM
equipment.

Adding all sorts of digital gadgets is quite a different matter. Now
you are adding functionality that will be available only to the
FM/digital community. This introduces potential safety and usability
issues. Stacking transmissions digitally isn't going to work when the
same transmissions must be mirrored on analog AM--and they have to be
if you want to maintain safety and keep controller workload
reasonable.

> One does _not_ need to implement any of the fancier capabilities that
> I mentioned. I stated them only as what could be easily done once the
> capability is in place.

A change from AM analog to anything else would be glacially slow, and
small steps are safest. I see a direct safety benefit in having the
clarity of FM transmission. I don't see a direct safety benefit in
having other unnecessary features, and I do see potential risks.

> Analog cell phones are being replaced with digital cell phones ...

Analog cell phones were replaced with digital well over a decade ago
throughout the world, except for a couple of countries.

> There would be no need to replace
> everything at once and I'm not sure why you think that would need to be the
> case.

The need arises as soon as you add new functionality.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Jim Logajan]

Larry Dighera > wrote:
> Because it is unlikely the FCC will agree to allocate additional
> frequency spectrum for the proposed new communications system.

The frequency allocation would need to be changed or added to on an
international scope, so I believe the operative organizations would be the
ITU and the ICAO or IATA - the FCC would simply enforce the change within
the U.S. Like you, I would have thought new allocations or changed
allocations would be hard, but changes are made every four years and in the
GHz range they seem to been more readily done; e.g.:

http://www.boeing.com/connexion/news/2003/q3/nr_030707j.html

[Dan Luke]

"Mxsmanic" wrote:

>> With regards to aviation communication, "niner" is the proper phonetic
>> pronunciation of nine and "fife" is the proper pronunciation of five,
>> although admittedly "fife" is not as widely used as it should be.
>
> They still sound very much the same.

********. One has two syllables, the other only one.

You haven't spent much time communicating via aircraft radios, have you?

--
Dan
C172RG at BFM

[Jim Logajan]

Mxsmanic > wrote:
> Switching from AM to FM doesn't involve incompatibilities. You can
> run both in parallel indefinitely, providing identical services (just
> as some commercial radio stations have broadcasts on both AM and FM
> simultaneously). Introducing FM doesn't obsolete any of the AM
> equipment.

Regarding your argument in the paragraph above and the one below...

> Adding all sorts of digital gadgets is quite a different matter. Now
> you are adding functionality that will be available only to the
> FM/digital community. This introduces potential safety and usability
> issues. Stacking transmissions digitally isn't going to work when the
> same transmissions must be mirrored on analog AM--and they have to be
> if you want to maintain safety and keep controller workload
> reasonable.

....honestly don't make any sense to me. In the first paragraph you see no
problem with two transmitters being used to transmit the same thing using
different frequencies and different modulation techniques, and in the
second paragraph you do. I think you could turn the first paragraph into
the second or vice-versa with appropriate special pleading - which is why
I'm confused about why you find a switch from AM to FM a better transition
than any other transition. I guess I just don't see what you see.

[Dan Luke]

"Peter R." wrote:

>
> With regards to aviation communication, "niner" is the proper phonetic
> pronunciation of nine and "fife" is the proper pronunciation of five,

There is newsreel footage from the fifties of a nuclear bomb test that
includes scenes from the control room. The guy calling the countdown
actually says "fiver". Talk about unclear on the concept!

--
Dan
C172RG at BFM

[Stefan]

Mxsmanic schrieb:

> I don't see why it would be so objectionable. It isn't even necessary
> that the AM be phased out. The FM would simply be available to those
> who wish to use it, for the added clarity it provides.

Yeah. One pilot talks on AM and the other listens to FM. Great idea.
Adds a lot of clarity to the communication.

Stefan

[[email protected]]

On Sat, 02 Sep 2006 21:08:49 GMT, B A R R Y
> wrote:

>On Sat, 02 Sep 2006 18:03:31 +0100, wrote:
>
>>
>>With FM the signal remains much clearer until the point where it
>>suddenly becomes unreadable when itl becomes weak.
>>
>>With AM is that readability gradually reduces as the signal gets
>>weaker. If you open the squelch you can often still read AM when FM
>>would be unreadable.
>
>That's the way I always understood it. AM transmissions can be pulled
>out of background noise. FM is more difficult, as it cuts out before
>it's unreadable.
>
>I would imagine digital would be the worst. Digital is either
>decodable and there or nothing and silence.
>
>This is all based on my experiences with aircraft AM radios, FM
>business radios, broadcast and satellite TV, and radio, so it might
>be all wrong. <G>

You're spot on with your comments. My experience is amateur radio with
AM/FM & SSB plus business radios, broadcast radio & TV FM/AM from
longwave to SHF.

Given the choice SSB gives best low signal readability but not very
suitable for normal aviation. The problem with comparisons is a 10watt
AM transmitter puts out 2x sidebands of 2.5watts (max). All of the
intelligence is available in one 2.5watt sideband, the rest is to make
the signal easier to decode. The equivalent 10watt FM transmittter
uses the full 10 watts but that's getting too technical:-)

At the end of the day if AM equipment is working properly there's not
a problem and there's no reason to change every transmitter in the
world. Probably the main problem is aircraft noise and poor hearing
along with microphone technique and peoples accents! I've flown mamy
aircraft in a number of countries and can't say there's a problem with
AM. More likely to have a problem with a controller rattling out an
instruction too fast. I doubt I've had more than a handful of
transmissions, in 15 years, I'd give worse than readability 4. Almost
always 5.

Normal communication quality is up to 4KHz audio response. As you get
older you loose the high frequencies anyway so forget hi-fi! My
hearing is only good to around 6KHz but when I was younger was around
16KHz. You only require 3KHz audio bandwidth and if pushed for maximum
readability and least bandwidth 2KHz but it sounds very harsh though
very readable.
The worst transmissions in the UK are the military who sometimes sound
like they're using throat mikes. Myself and another aircraft were
working one military controller who was almost impossible to
understand. I could just make him out but the commercial aircraft gave
up. I'd say readability 2.

David

[Jim Logajan]

"Dan Luke" > wrote:
> There is newsreel footage from the fifties of a nuclear bomb test that
> includes scenes from the control room. The guy calling the countdown
> actually says "fiver". Talk about unclear on the concept!

Maybe he did it because unclear is an anagram of nuclear?

;-)

[Jim Logajan]

Stefan > wrote:
> Mxsmanic schrieb:
>
>> I don't see why it would be so objectionable. It isn't even necessary
>> that the AM be phased out. The FM would simply be available to those
>> who wish to use it, for the added clarity it provides.
>
> Yeah. One pilot talks on AM and the other listens to FM. Great idea.
> Adds a lot of clarity to the communication.

Huh? How is that problem different from something transmitting on 121.5 MHz
and someone else listening on 406 MHz?

Why is having multiple channels all using AM not a problem but if one added
more channels using a different modulation now suddenly presenting a
communication problem?

[Vaughn Simon]

"Jim Logajan" > wrote in message
.. .
> "Vaughn Simon" > wrote:
>> But changing to FM would require a new radio to be
>> simultaneously installed in every cockpit in the world. The only way
>> to accomplish that would be for every plane with a new radio to
>> transmit in "parallel" (as someone already suggested) for a period of
>> years on both the new mode and the old mode.
>
> That need not be the case, as evidenced by dual-mode cell phones that allow
> access to analog and digital cell sites,

The problem I was thinking of that is solved by parallel operation is where
you have two planes in the same pattern who can't hear each other because their
radios are not compatible. The only way I know to solve that is dual (parallel)
operation.

A good example of that concept is what they are doing with TV today. Many TV
stations are transmitting in both analog and digital (HD) so that we are covered
no matter what type of receiver we happen to own.

Vaughn

[Bob Noel]

In article >,
Jim Logajan > wrote:


> That would definitely be a great solution, but that page was last updated
> January 4, 2000. Do you or anyone else know if any further progress been
> made or have the efforts died? (The links I could find all seemed to dead-
> end.)

VDL mode 2 will be coming Real Soon Now. Like all the recent CNS/ATM
mandates/changes (RVSM, 8.33, TCAS, FM immunity, TAWS, BRNAV, RNP-4,
etc etc), the move to VDL is happening way way WAY later than originally
planned by the Big Thinkers.

--
Bob Noel
Looking for a sig the
lawyers will hate

[Matt Barrow]

"Bob Noel" > wrote in message
...
> In article >,
> Jim Logajan > wrote:
>
>
>> That would definitely be a great solution, but that page was last updated
>> January 4, 2000. Do you or anyone else know if any further progress been
>> made or have the efforts died? (The links I could find all seemed to
>> dead-
>> end.)
>
> VDL mode 2 will be coming Real Soon Now. Like all the recent CNS/ATM
> mandates/changes (RVSM, 8.33, TCAS, FM immunity, TAWS, BRNAV, RNP-4,
> etc etc), the move to VDL is happening way

"Sir? If the VP is such a VIP, then shouldn't we keep the PC on the QT?
Because if word leaks to the VC he could end up MIA and we'll all be put on
KP."

[Emily[_1_]]

Mxsmanic wrote:
> Peter R. writes:
>
>> A leading cause of accidents? Where did you get this statistic?
>
> From the NTSB and several books on the subject.

Could you provide a source? I've never heard this and I know several
NTSB employees.

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> Really? Can you cite some statistics? I'd be very interested in
>> reading them.
>
> Just look through accident and incident reports. Radio communication
> is one of the weak links in the aviation safety chain.
>
Has it ever been listed as a probable cause by the NTSB?

[Emily[_1_]]

Mxsmanic wrote:
> Peter R. writes:
>
>> A leading cause of accidents? Where did you get this statistic?
>
> From the NTSB and several books on the subject.
>
>> Guess? If a pilot or controller is not able to comprehend the other side's
>> transmission, there is no guess. "Say again?" is the phrase of choice and
>> it is used all over the frequencies.
>
> It's routine in linguistics to unconsciously guess. A person
> listening to familiar sounds in a familiar context will "fill in the
> blanks" for any sounds that cannot be unambiguously distinguished, and
> he will do this without thinking. If he guesses wrong, trouble can
> result, and accidents have happened in aviation for this reason (the
> most famous probably being the one at Tenerife).
>

Actually, in the Tenerife accident, the only radio problem was caused by
simultaneous radio transmissions by aircraft, NOT a pilot hearing want
he wanted to hear. The tower told the KLM aircraft to stand by at the
same time the Pan Am aircraft transmitted, which resulted in a blocking
of both transmissions. There were many other steps in the accident
chain, but Tenerife was most certainly not caused by a pilot hearing
what he wanted to hear.

[Emily[_1_]]

Mxsmanic wrote:
> Peter R. writes:
>
>> My understanding of the accident at Tenerife is that it had more to do with
>> a fateful heterodyne and a captain who was asserting his own way, rather
>> than misunderstood communications.
>
> Some of the words on the cockpit recording are impossible to
> understand even today. That's pretty strong evidence that
> misunderstood communications had an important role in this accident.
> In fact, there are several instances of misunderstood radio
> communication involved.
>

They were misunderstood a) because people were stepping on other people
and b) because the KLM crew had heavy Dutch accents. Please do a little
research before you assert such ridiculous accusations.

[Emily[_1_]]

Mxsmanic wrote:
> Peter R. writes:
>
>> With regards to aviation communication, "niner" is the proper phonetic
>> pronunciation of nine and "fife" is the proper pronunciation of five,
>> although admittedly "fife" is not as widely used as it should be.
>
> They still sound very much the same.
>
Uh, no they don't.

[Dave Stadt]

"Emily" > wrote in message
...
> Mxsmanic wrote:
>> Peter R. writes:
>>
>>> A leading cause of accidents? Where did you get this statistic?
>>
>> From the NTSB and several books on the subject.
>>
>>> Guess? If a pilot or controller is not able to comprehend the other
>>> side's
>>> transmission, there is no guess. "Say again?" is the phrase of choice
>>> and
>>> it is used all over the frequencies.
>>
>> It's routine in linguistics to unconsciously guess. A person
>> listening to familiar sounds in a familiar context will "fill in the
>> blanks" for any sounds that cannot be unambiguously distinguished, and
>> he will do this without thinking. If he guesses wrong, trouble can
>> result, and accidents have happened in aviation for this reason (the
>> most famous probably being the one at Tenerife).
>>
>
> Actually, in the Tenerife accident, the only radio problem was caused by
> simultaneous radio transmissions by aircraft, NOT a pilot hearing want he
> wanted to hear. The tower told the KLM aircraft to stand by at the same
> time the Pan Am aircraft transmitted, which resulted in a blocking of both
> transmissions. There were many other steps in the accident chain, but
> Tenerife was most certainly not caused by a pilot hearing what he wanted
> to hear.

Correct, and FM would not have solved any of the problems. At least with AM
the heterodyne lets people know there were multiple simultaneous
transmissions. The capture characteristics of FM do away with this
sometimes useful feature.

[Dave Stadt]

"Steven P. McNicoll" > wrote in message
ink.net...
>
> "Ron Natalie" > wrote in message
> m...
>>
>> No actually, it's just historical. Early av radio used AM, and for that
>> reason we still do.
>>
>
> Didn't all early radio use AM?

Nope, it was quite a ways down the line. Morse code via spark gap
transmitters was one of the first.

[Dave Stadt]

"Mxsmanic" > wrote in message
...
> Vaughn Simon writes:
>
>> Actually, not much does change in aviation compared with other fields of
>> human endeavor.
>
> I don't think that is necessarily a bad thing. It does worry me that
> the things that change in aviation are things that I'd rather see
> stable. I have my doubts about fly-by-wire systems or glass cockpits,
> which seem to be increasingly designed for the convenience of
> programmers who grew up with Windows rather than for the convenience
> of pilots.
>
>> But changing to FM would require a new radio to be
>> simultaneously installed in every cockpit in the world. The only way to
>> accomplish that would be for every plane with a new radio to transmit in
>> "parallel" (as someone already suggested) for a period of years on both
>> the new
>> mode and the old mode. What are the chances of AOPA allowing that to
>> happen?
>
> I don't see why it would be so objectionable. It isn't even necessary
> that the AM be phased out. The FM would simply be available to those
> who wish to use it, for the added clarity it provides.

Why screw around with FM. It is old technology, not much beter than AM,
and there are much better technologies that would cure the communication
problems and lack of frequency availibility.

[Emily[_1_]]

Dave Stadt wrote:
> "Emily" > wrote in message
> ...
>> Mxsmanic wrote:
>>> Peter R. writes:
>>>
>>>> A leading cause of accidents? Where did you get this statistic?
>>> From the NTSB and several books on the subject.
>>>
>>>> Guess? If a pilot or controller is not able to comprehend the other
>>>> side's
>>>> transmission, there is no guess. "Say again?" is the phrase of choice
>>>> and
>>>> it is used all over the frequencies.
>>> It's routine in linguistics to unconsciously guess. A person
>>> listening to familiar sounds in a familiar context will "fill in the
>>> blanks" for any sounds that cannot be unambiguously distinguished, and
>>> he will do this without thinking. If he guesses wrong, trouble can
>>> result, and accidents have happened in aviation for this reason (the
>>> most famous probably being the one at Tenerife).
>>>
>> Actually, in the Tenerife accident, the only radio problem was caused by
>> simultaneous radio transmissions by aircraft, NOT a pilot hearing want he
>> wanted to hear. The tower told the KLM aircraft to stand by at the same
>> time the Pan Am aircraft transmitted, which resulted in a blocking of both
>> transmissions. There were many other steps in the accident chain, but
>> Tenerife was most certainly not caused by a pilot hearing what he wanted
>> to hear.
>
> Correct, and FM would not have solved any of the problems. At least with AM
> the heterodyne lets people know there were multiple simultaneous
> transmissions. The capture characteristics of FM do away with this
> sometimes useful feature.

I think it's very useful. As annoying as it is to have someone out
there with a stuck mic, what would happen if messages were stepped on
and we didn't know it?

[Dave Stadt]

"Mxsmanic" > wrote in message
...
> Emily writes:
>
>> Really? Can you cite some statistics? I'd be very interested in
>> reading them.
>
> Just look through accident and incident reports. Radio communication
> is one of the weak links in the aviation safety chain.
>
> --
> Transpose mxsmanic and gmail to reach me by e-mail.

I read NTSB reports every day for years. I cannot remember communications
being anything more than down in the noise level as far as an accident cause
and it certainly is not a leading cause of accidents.

[Dave Stadt]

"Emily" > wrote in message
. ..
> Mxsmanic wrote:
>> Emily writes:
>>
>>> Really? Can you cite some statistics? I'd be very interested in
>>> reading them.
>>
>> Just look through accident and incident reports. Radio communication
>> is one of the weak links in the aviation safety chain.
>>
> Has it ever been listed as a probable cause by the NTSB?

I have read thousands of NTSB reports and cannot remember one. Could be a
little CRS in there but not much.

[James Robinson]

Emily > wrote:

> The tower told the KLM aircraft to stand by at the same time the Pan
> Am aircraft transmitted, which resulted in a blocking of both
> transmissions. There were many other steps in the accident chain, but
> Tenerife was most certainly not caused by a pilot hearing what he
> wanted to hear.

Then why did the aircraft start its takeoff roll, if the pilot didn't hear
what he wanted to? The tower only issued the ATC clearance, and the KLM
captain seems to have taken that as permission to take off. What else is
that but hearing what he wanted to?

[Thomas Borchert]

Mxsmanic,

> I have my doubts about fly-by-wire systems or glass cockpits,
> which seem to be increasingly designed for the convenience of
> programmers who grew up with Windows rather than for the convenience
> of pilots.
>

Sorry, but that's just plain BS.

--
Thomas Borchert (EDDH)

[Mxsmanic]

Emily writes:

> They were misunderstood a) because people were stepping on other people
> and b) because the KLM crew had heavy Dutch accents.

The reasons why they were misunderstood have never been ascertained,
and there are several possibilities. It's not even clear how much was
understood or misunderstood, since a number of the people involved are
dead. The common point to all the possible scenarios is misunderstood
radio communication.

--
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[Mxsmanic]

Emily writes:

> Actually, in the Tenerife accident, the only radio problem was caused by
> simultaneous radio transmissions by aircraft, NOT a pilot hearing want
> he wanted to hear.

There were several problems. The Pan Am crew was not sure of which
exit to take from the runway. Neither was the KLM, IIRC. The KLM
didn't understand the ATC clearance, and the tower didn't understand
the KLM acknowledgement. Pam Am said it was on the runway several
times but this was misunderstood as well. There were many
misunderstandings, most of them related to radio communication.

> The tower told the KLM aircraft to stand by at the
> same time the Pan Am aircraft transmitted, which resulted in a blocking
> of both transmissions.

Not entirely true. Part of it was audible.

> There were many other steps in the accident
> chain, but Tenerife was most certainly not caused by a pilot hearing
> what he wanted to hear.

That has never been determined. The most likely cause is that a pilot
heard what he wanted to hear, or he deliberately and negligently
ignored instructions. Other pilots may also have heard what they
wanted to hear.

--
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[Mxsmanic]

Dave Stadt writes:

> Nope, it was quite a ways down the line. Morse code via spark gap
> transmitters was one of the first.

All early audio used AM.

--
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[Mxsmanic]

Stefan writes:

> Yeah. One pilot talks on AM and the other listens to FM. Great idea.
> Adds a lot of clarity to the communication.

It adds more than you would have with both pilots using AM.

However, you're not supposed to listen to other pilots; you're
supposed to listen to controllers. All conversations are air-ground,
not air-air.

--
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[Mxsmanic]

Dave Stadt writes:

> Why screw around with FM. It is old technology, not much beter than AM,
> and there are much better technologies that would cure the communication
> problems and lack of frequency availibility.

Such as?

--
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[Mxsmanic]

Thomas Borchert writes:

> Sorry, but that's just plain BS.

Famous last words.

--
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[Mxsmanic]

Larry Dighera writes:

> I would guess that noise-blanker and noise-limiting circuits are
> incorporated in the current radio designs.

You can't actively remove noise over a radio channel because you have
no unique identifier of noise vs. information. Noise-reduction
headsets work because they know what is noise (outside sound) and what
isn't (audio being played through the headset).

> Other than the occasional heterodyne squeal that occurs in the
> receiver when two transmitters are transmitting on the same frequency
> simultaneously, there shouldn't be any other noise. Ignition noise
> should be suppressed by Faraday shielding, and generator/alternator
> noise should be bypassed to ground.

Anything that isn't signal is noise. AM transmissions are fuzzy and
hard to hear. In fact, aviation AM radio is probably the noisiest
type of radio voice communication still in use. Most other types of
radio communication today are FM.

> What is the nature of the noise you are hearing? Can you describe it?
> Is it a hum, pulses, growling, squealing, what?

White noise. It doesn't come from anything within the aircraft or
station.

> Regardless of when it occurs, there will ultimately be an additional
> cost.

Sure, but one that companies and individuals can assume on a phased
basis at their convenience.

The fact that transponders and VORs exist today (when they did not in
the early days of aviation) proves that this works.

> And to expect the old (current) communications system to remain
> operational while the new system you are proposing is operating
> concurrently won't be feasible if they use the same frequencies.

Presumably they would use different frequencies.

> If an new alternate frequency band is used for the new communications
> system you are proposing, it could work. But getting the FCC to
> allocate additional frequency spectrum will probably be opposed,
> because the frequency spectrum is a finite resource, and there are
> many more services desiring to use it than there is bandwidth
> available.

Aviation is a pretty critical use of bandwidth.

> You really should read the information at some of the links I provided
> to get an idea of what has been tried, and what is on the FAA's
> horizon regarding aviation communications. This topic has been very
> thoroughly researched by government personnel and it's unlikely that
> you will hit upon a superior system to what the professionals have
> examined.

How much of aviation was designed by "professionals"?

--
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[Mxsmanic]

Dan Luke writes:

> ********. One has two syllables, the other only one.

There's a lot more to human speech than syllables. Only a single
phoneme separates the two in many pronunciations (particularly because
restricted bandwidth can limit the intelligibility of fricative
consonants), and that phoneme sounds very much like an unstressed
central hesitation vowel, which means it may not be heard at all.
This is especially true for non-rhotic speakers.

> You haven't spent much time communicating via aircraft radios, have you?

How much time have you spent studying phonetics and linguistics? They
are just as relevant here as experience with aircraft radios.

However, I don't think a wealth or dearth of experience in any domain
need be a prerequisite to discussion. And I think it more productive
to discuss the topic at hand than to direct personal attacks at anyone
with whom one disagrees.

--
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[Mxsmanic]

Jim Logajan writes:

> ...honestly don't make any sense to me. In the first paragraph you see no
> problem with two transmitters being used to transmit the same thing using
> different frequencies and different modulation techniques, and in the
> second paragraph you do.

The second instance involves additional or different information being
transmitted over one channel, but not the other. The first instance
involves only a reduction of noise; the information content is the
same in both channels.

> I think you could turn the first paragraph into
> the second or vice-versa with appropriate special pleading - which is why
> I'm confused about why you find a switch from AM to FM a better transition
> than any other transition. I guess I just don't see what you see.

I don't know if it's better than any other transition; I just think
that something should be done to improve the archaic system that
exists now.

--
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[Stefan]

Mxsmanic schrieb:

> However, you're not supposed to listen to other pilots; you're
> supposed to listen to controllers. All conversations are air-ground,
> not air-air.

You haven't ever actually flown a plane, have you?

Stefan

[Stefan]

Emily schrieb:

> There were many other steps in the accident
> chain, but Tenerife was most certainly not caused by a pilot hearing
> what he wanted to hear.

Actually, the KLM captain hearing what he wanted to hear was most
certainly the main cause for that accident.

As a consequence of this misunderstanding, the word "take-off" shall now
only be used in "cleared for take off" and in the read-back of this
clearance, or, at uncontrolled airfields, when a pilot says that he is
taking off. No more "ready for take off", "stand by for take off" and
the like, and no taking off before you are absolutely positively sure
that you have heard and read back the word.

But all this had nothing to do with the readability of the radio
transmissions.

Stefan

[Greg Copeland[_1_]]

On Sat, 02 Sep 2006 20:19:15 +0200, Mxsmanic wrote:

> Jim Logajan writes:
>
> <details snipped>
>
>> Maybe someday the FAA and/or ICAO will consider replacing analog radios
>> with a more capable digital system....
>
> All very interesting, but one of the criteria that any new system
> would have to satisfy is that it would have to work in parallel with
> the existing system. Adding features to the new system that are not
> available in the old system would create dangerous differences between
> the two. Seeing fancy displays in the ATC or tower for the lucky
> digital users won't help deal with traffic from old AM users, and it
> might even confuse things enough to cause problems.
>
> A highly advanced solution would require replacing everything at once,
> which isn't going to happen. A simpler solution that just provides
> better quality audio could coexist with older systems without a
> problem.

New systems (P25) already do this type of thing. I develop digital radio
systems. Police, fire, FBI, CIA, DoD, DoE, various municipal
utilities, and various branches of the military are all taking advantage
of this technology. In many cases, the old analog systems must co-exist
with the newer P25 systems. In some cases, more rural analog systems
actually connect with a P25 network via a specialized repeated.
Integration is not a problem.

Last I read, an FAA study indicated they need lots and lots of money
(sorry, don't remember the amount) to upgrade their infrastructure from
analog to digital. The sad thing is, it does not appear Congress is going
to give it to them. Worse, the same report indicates, over the next
10-years, the FAA will exceed their required conversion dollars by simply
maintaining and repair their existing, archaic, analog infrastructure. In
other words, the FAA needs to do something...even if they are simply
updating their existing analog infrastructure. Regardless, the money does
not appear to be available.

Advantages of this technology include:
o call queuing - meaning, PTT places you in a queue so you can get a word
in, even when the controllers are very busy. BTW, this also means no more
"walked on" transmissions.

o call prioritization - All sorts of cool things can be done here -
including, most recent exchange receives priority. Also, should IFR
traffic receive higher priority over that of VFR? What about commercial
traffic? Priority could be adjusted dynamically too. This means
planes in distress could be assigned higher priority. So on and so on...

o hang timer detection - a stuck PTT is not going to lock everyone out

o caller id - imagine your tail number, altimeter, heading, and aircraft
type provided to the controller on every PTT.

o MUCHO better frequency utilization

o Limited data services

The list could go on and on...needless to say, digital has some neat
features.

The only con of digitial compared to analog is reception. With analog,
you can hear a weak signal. It may sound like absoluete crap, but you can
still hear it. With digitial, either you have a strong enough signal to
hear it...and it sounds awesome...or you hear absoluetely nothing at all.

Greg

[Dan Luke]

"Mxsmanic" wrote:

>> ********. One has two syllables, the other only one.
>
> There's a lot more to human speech than syllables. Only a single
> phoneme separates the two in many pronunciations (particularly because
> restricted bandwidth can limit the intelligibility of fricative
> consonants), and that phoneme sounds very much like an unstressed
> central hesitation vowel, which means it may not be heard at all.
> This is especially true for non-rhotic speakers.

That is why we say "niner." In practice, it works very well to distinguish
nine from five..

>> You haven't spent much time communicating via aircraft radios, have you?
>
> How much time have you spent studying phonetics and linguistics? They
> are just as relevant here as experience with aircraft radios.

One semester in college. My guess is that's a lot longer than you've spent
talking to ATC.

> However, I don't think a wealth or dearth of experience in any domain
> need be a prerequisite to discussion. And I think it more productive
> to discuss the topic at hand than to direct personal attacks at anyone
> with whom one disagrees.

When it becomes apparent that an argument is born of ignorance, it is
appropriate to point that out. That is not a personal attack. I did not
impugn your character, merely noted the obvious: WRT aircraft radio
communications, you do not know what you are talking about.

You began this thread with the unfounded assertion that "improper and
misunderstood radio communication is a leading cause of accidents." When
Emily challenged you for evidence, you used the old, lame usenet dodge of
telling her to look it up herself. Since then, you have attempted to create
an argument based on phonetics to support a faulty premise. Your five vs.
niner attempt is the weakest yet, and you would not even have tried it if
you had any experience on the radio.

--
Dan
C172RG at BFM

[Dan Luke]

"Mxsmanic" wrote:
>
>> I would guess that noise-blanker and noise-limiting circuits are
>> incorporated in the current radio designs.
>
> You can't actively remove noise over a radio channel because you have
> no unique identifier of noise vs. information.

******** again. I have a radio that does actively remove noise--it has a
button to turn the feature on and off, and it works quite well.

I'll say one thing for you, you are fearless in your ignorance.

--
Dan
C172RG at BFM

[Mxsmanic]

Greg Copeland writes:

> New systems (P25) already do this type of thing. I develop digital radio
> systems. Police, fire, FBI, CIA, DoD, DoE, various municipal
> utilities, and various branches of the military are all taking advantage
> of this technology. In many cases, the old analog systems must co-exist
> with the newer P25 systems. In some cases, more rural analog systems
> actually connect with a P25 network via a specialized repeated.
> Integration is not a problem.

So why wouldn't it extend to aviation?

> Last I read, an FAA study indicated they need lots and lots of money
> (sorry, don't remember the amount) to upgrade their infrastructure from
> analog to digital.

They need not upgrade it all at once.

> The sad thing is, it does not appear Congress is going
> to give it to them.

Congress, like most of America, is hysterical about imaginary human
threats these days, and has probably lost track of the much more
mundane but much more serious safety risks associated with
infrastructure, aircraft, and crews.

> Advantages of this technology include:
> o call queuing - meaning, PTT places you in a queue so you can get a word
> in, even when the controllers are very busy. BTW, this also means no more
> "walked on" transmissions.

Do other aircraft hear the transmission when you make it, or when the
controller hears it? Granted, they are only supposed to listen to the
controller, but in practice they will be listening to other aircraft
as well.

How do you make this work in parallel with analog systems that cannot
queue?

> o call prioritization - All sorts of cool things can be done here -
> including, most recent exchange receives priority. Also, should IFR
> traffic receive higher priority over that of VFR? What about commercial
> traffic? Priority could be adjusted dynamically too. This means
> planes in distress could be assigned higher priority. So on and so on...

It's best not to jump off the deep end with gadgets. Just because
something can be done doesn't mean that it should be done.

> o caller id - imagine your tail number, altimeter, heading, and aircraft
> type provided to the controller on every PTT.

Where does this leave people with analog equipment?

> o Limited data services

What kind of data services do pilots need? Are they going to be
surfing the Web?

> The list could go on and on...needless to say, digital has some neat
> features.

Neat features aren't necessarily desirable features. There is too
much of a tendency to bloat digital systems with features that have
been hastily designed, inadequately analyzed, and barely tested at
all.

> The only con of digitial compared to analog is reception. With analog,
> you can hear a weak signal. It may sound like absoluete crap, but you can
> still hear it. With digitial, either you have a strong enough signal to
> hear it...and it sounds awesome...or you hear absoluetely nothing at all.

If the digital threshold is set where the threshold of intelligibility
would be in analog, there's no net loss.

--
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[Dan Luke]

"Thomas Borchert" wrote:

> Mxsmanic,
>
>> I have my doubts about fly-by-wire systems or glass cockpits,
>> which seem to be increasingly designed for the convenience of
>> programmers who grew up with Windows rather than for the convenience
>> of pilots.
>>
>
> Sorry, but that's just plain BS.

He's got a ton of it to spread around.

--
Dan
C172RG at BFM

[Mxsmanic]

Dan Luke writes:

> ******** again. I have a radio that does actively remove noise--it has a
> button to turn the feature on and off, and it works quite well.

What kind of noise does it remove, and how does it distinguish noise
from signal?

--
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[Vaughn Simon]

"Mxsmanic" > wrote in message
...
> Dave Stadt writes:
>
>> Why screw around with FM. It is old technology, not much beter than AM,
>> and there are much better technologies that would cure the communication
>> problems and lack of frequency availibility.
>
> Such as?

Such as VOIP actually, or other digital technologies that are now quite
common, cheap, and "off the shelf". In police and fire communications, FM is
quickly giving away to digital modes. My bad for previously talking about FM as
if it were the only possibility.

A digital-capable radio does not care if it is transmitting voice or data, so it
could someday allow truly automated flight control. For example, you might be
able to get clearance into controlled airspace automatically and have it show up
as a green dotted line on your MFD, to be acknowledged with the mere push of a
button.

[Larry Dighera]

On Sun, 03 Sep 2006 13:33:36 +0200, Mxsmanic >
wrote in >:

>
>However, you're not supposed to listen to other pilots; you're
>supposed to listen to controllers. All conversations are air-ground,
>not air-air.

You'll have to cite a source for this nugget of knowledge. Are you
familiar with Common Traffic Advisory Frequency (CTAF)?

[Mxsmanic]

Vaughn Simon writes:

> Such as VOIP actually, or other digital technologies that are now quite
> common, cheap, and "off the shelf". In police and fire communications, FM is
> quickly giving away to digital modes.

I doubt that they are using VoIP, though, which is notoriously
unreliable.

I'm not sure that cheap, common or "off-the-shelf" should be the top
criteria for choosing a replacement for AM radio. I think "safe"
should be the highest priority. If it improves safety, it's good; if
it doesn't, it's bad (unless it can improve something else _without_
compromising safety).

> A digital-capable radio does not care if it is transmitting voice or data, so it
> could someday allow truly automated flight control. For example, you might be
> able to get clearance into controlled airspace automatically and have it show up
> as a green dotted line on your MFD, to be acknowledged with the mere push of a
> button.

But then you won't need pilots. Actually, it is nearly possible to do
without them today--but radio communication is still one of the
sticking points.

--
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[Mxsmanic]

Larry Dighera writes:

> You'll have to cite a source for this nugget of knowledge.

FAA AIMs and CFRs make it pretty clear that communications involving a
controller are pilot-controller exchanges, not pilot-pilot exchanges.

> Are you familiar with Common Traffic Advisory Frequency (CTAF)?

Yes, but it and similar schemes don't involve a controller, so
obviously the communication is between aircraft directly.

--
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[Dan Luke]

"Mxsmanic" wrote:

> Dan Luke writes:
>
>> ******** again. I have a radio that does actively remove noise--it has a
>> button to turn the feature on and off, and it works quite well.
>
> What kind of noise does it remove, and how does it distinguish noise
> from signal?

It removes a lot of the static noise. I do not know the technical details
of how it does it. However, the freqencies of human speech do not cover the
audible spectrum, and all extraneous frequencies may be filtered quite
easily. Even frequencies at the upper and lower ends of human speech may be
filtered with minimal effect on intelligibility. Perhaps it's as simple as
that.

--
Dan
C172RG at BFM

[Dan Luke]

"Mxsmanic" wrote:

>
> However, you're not supposed to listen to other pilots; you're
> supposed to listen to controllers.

Utter nonsense.

It will be entertaining to see what bs you come up with next.

--
Dan
C172RG at BFM

[Vaughn Simon]

"Mxsmanic" > wrote in message
...
> Vaughn Simon writes:
>
>> Such as VOIP actually, or other digital technologies that are now quite
>> common, cheap, and "off the shelf". In police and fire communications, FM is
>> quickly giving away to digital modes.
>
> I doubt that they are using VoIP, though, which is notoriously
> unreliable.

You should a bit of reading before you make such comments. I happen to be in
the public safety communications field, and we are right now phasing out our old
trunked FM system for a VOIP system. We have already scrapped our old phone
systems in favor of VOIP and that is working just fine. If VOIP were
"notoriously unreliable" we would hardly use it for public safety
communications.

Vaughn

[Mxsmanic]

Vaughn Simon writes:

> You should a bit of reading before you make such comments. I happen to be in
> the public safety communications field, and we are right now phasing out our old
> trunked FM system for a VOIP system. We have already scrapped our old phone
> systems in favor of VOIP and that is working just fine. If VOIP were
> "notoriously unreliable" we would hardly use it for public safety
> communications.

Wait and see.

--
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[Mxsmanic]

Dan Luke writes:

> It removes a lot of the static noise. I do not know the technical details
> of how it does it. However, the freqencies of human speech do not cover the
> audible spectrum, and all extraneous frequencies may be filtered quite
> easily. Even frequencies at the upper and lower ends of human speech may be
> filtered with minimal effect on intelligibility. Perhaps it's as simple as
> that.

A noise-reduction system can make some assumptions about what is
_probably_ noise and what is _probably_ signal, but in most cases it
will drop at least part of the signal.

You need at least about 4 KHz for speech, but some sibilants have
components that go as high as 8 KHz or so, and if you chop off the
high frequencies the sibilants may be lost. Thus, 'f' and 's' might
start to sound the same, because the difference between them is in the
high frequencies.

Using fixed phraseology helps a lot, because it is highly redundant.
However, there is still the potential for confusion in relatively
random, non-redundant communications, such as strings of digits or
letters.

--
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[[email protected]]

On Sun, 03 Sep 2006 13:39:09 +0200, Mxsmanic >
wrote:

>Larry Dighera writes:
>
--- cut-----

>Anything that isn't signal is noise. AM transmissions are fuzzy and
>hard to hear. In fact, aviation AM radio is probably the noisiest
>type of radio voice communication still in use. Most other types of
>radio communication today are FM.
>

This thread is becoming a lot of guessing and not based on facts!
I doubt anybody has evaluated AM compared to FM in an aircraft so
won't know what the effects are when tried side by side.

There is absolutely no difference in qualilty between AM & FM if they
are designed to the same specification. If you modulate an AM or FM
transmitter with up to 3KHx of audio they will sound identical. What
you put into the transmitter comes out of the receiver assuming there
isn't a fault.

FM maintains a low background noise longer than AM and the only
difference is at low signal levels when FM very quickly becomes
totally unreadable. AM can still be heard and understood, depending on
the ability of the person listening. With all the noise in an aircraft
a little bit of low level background noise is not significant.

Digital has some merit but again when the signal reaches a threshold
it stops completely.

The whole thread is futile as the centre of the 'aviation universe'
may well be the US but you aren't going to get the rest of the world
to change. Even having regultions which are supposed to be accepted
worldwide doesn't work. Most counties have exceptions.

About the only thing which is standard is the use of the English
language. Even then the locals will use their own language! Have you
ever worked controllers with Spanish English, Finnish English,
Canadian English, New Zealand English, Cyprus English, Bahamian,
Caribbean or even Amereican English. That's where the differences can
be heard. AM radio is adequate for the job and if you don't think so
then get your installation checked out by a qualified engineer, you
may be suprised.

As for increasing the number of frequencies Europe has introduced
8.3KHz spacing. Fortunately at the lower GA flight levels it's not
required but the higher commercials now require new radios.

Most radios are dual NAV/COM so not only would you need a new COM but
a new NAV too... It isn't going to happen...!

[Emily[_1_]]

James Robinson wrote:
> Emily > wrote:
>
>> The tower told the KLM aircraft to stand by at the same time the Pan
>> Am aircraft transmitted, which resulted in a blocking of both
>> transmissions. There were many other steps in the accident chain, but
>> Tenerife was most certainly not caused by a pilot hearing what he
>> wanted to hear.
>
> Then why did the aircraft start its takeoff roll, if the pilot didn't hear
> what he wanted to? The tower only issued the ATC clearance, and the KLM
> captain seems to have taken that as permission to take off. What else is
> that but hearing what he wanted to?

He didn't hear ANYTHING but a heterodyne. If you want to say he heard
the heterodyne as clearance to take off, fine, but that's not what we're
talking about. The OP stated that AM results in poor transmission
quality and therefore pilots will hear what they want to hear. In this
case, the pilots heard nothing, and a high ranking captain blatantly
ignored both ATC and his own f/e.

[Emily[_1_]]

Mxsmanic wrote:
> Vaughn Simon writes:
>
>> Actually, not much does change in aviation compared with other fields of
>> human endeavor.
>
> I don't think that is necessarily a bad thing. It does worry me that
> the things that change in aviation are things that I'd rather see
> stable. I have my doubts about fly-by-wire systems or glass cockpits,
> which seem to be increasingly designed for the convenience of
> programmers who grew up with Windows rather than for the convenience
> of pilots.

Do you have any connection to aviation at all?

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> They were misunderstood a) because people were stepping on other people
>> and b) because the KLM crew had heavy Dutch accents.
>
> The reasons why they were misunderstood have never been ascertained,
> and there are several possibilities. It's not even clear how much was
> understood or misunderstood, since a number of the people involved are
> dead. The common point to all the possible scenarios is misunderstood
> radio communication.
>
Because of a heterodyne, NOT poor radio transmission quality. As
someone else already pointed out, FM doesn't even have this useful quality.

And yes, the official probable cause lists the heterodyne. I thought
you would have known that, seeing as you know allegedly read all these
accident reports.

(And since one full flight crew survived, that's pretty good eyewitness
account)

[Emily[_1_]]

Mxsmanic wrote:
> Thomas Borchert writes:
>
>> Sorry, but that's just plain BS.
>
> Famous last words.
>

Speaking as someone who works for an OEM that works with the latest
cutting edge technology, Thomas is entirely correct.

[Emily[_1_]]

Stefan wrote:
> Emily schrieb:
>
>> There were many other steps in the accident chain, but Tenerife was
>> most certainly not caused by a pilot hearing what he wanted to hear.
>
> Actually, the KLM captain hearing what he wanted to hear was most
> certainly the main cause for that accident.
>
> As a consequence of this misunderstanding, the word "take-off" shall now
> only be used in "cleared for take off" and in the read-back of this
> clearance, or, at uncontrolled airfields, when a pilot says that he is
> taking off. No more "ready for take off", "stand by for take off" and
> the like, and no taking off before you are absolutely positively sure
> that you have heard and read back the word.
>
> But all this had nothing to do with the readability of the radio
> transmissions.
>
> Stefan
That was my point. He heard what he wanted to hear, but not because of
jarbled radio transmission.

[Emily[_1_]]

Mxsmanic wrote:
> Larry Dighera writes:
>
>> You'll have to cite a source for this nugget of knowledge.
>
> FAA AIMs and CFRs make it pretty clear that communications involving a
> controller are pilot-controller exchanges, not pilot-pilot exchanges.
>
>> Are you familiar with Common Traffic Advisory Frequency (CTAF)?
>
> Yes, but it and similar schemes don't involve a controller, so
> obviously the communication is between aircraft directly.
>

But you just said that all communications are air-ground. You can't
back pedal.

[Stefan]

Emily schrieb:

> He didn't hear ANYTHING but a heterodyne.


Wrong. Please read the NTSB report before making such statements.


1705:53.4 APP KLM eight seven * zero five uh you are cleared to the
Papa Beacon climb to and maintain flight level nine zero right turn
after take-off proceed with heading zero four zero until intercepting
the three two five radial from Las Palmas VOR. (1706:08.2)

1706:09.6 KLM Ah roger, sir, we're cleared to the Papa Beacon flight
level nine zero, right turn out zero four zero until intercepting the
three two five and we're now (at take-off). (1706:17.9)


Of course this has nothing to do with the readablility of the transmission.

Stefan

[Vaughn Simon]

"Mxsmanic" > wrote in message
...
>
> Wait and see.

I try to remain civil here on the Usenet, but you have proven all through
this thread to not be someone worth wasting time on. You get the last word, but
thanks to technology I won't be seeing it.

Bye
Vaughn


> Transpose mxsmanic and gmail to reach me by e-mail.
Why would I want to do that?

[Emily[_1_]]

Stefan wrote:
> Emily schrieb:
>
>> He didn't hear ANYTHING but a heterodyne.
>
>
> Wrong. Please read the NTSB report before making such statements.

I have read the report, and I don't see where readability came in.

> 1705:53.4 APP KLM eight seven * zero five uh you are cleared to the
> Papa Beacon climb to and maintain flight level nine zero right turn
> after take-off proceed with heading zero four zero until intercepting
> the three two five radial from Las Palmas VOR. (1706:08.2)
>
> 1706:09.6 KLM Ah roger, sir, we're cleared to the Papa Beacon flight
> level nine zero, right turn out zero four zero until intercepting the
> three two five and we're now (at take-off). (1706:17.9)

I think there was some confusion here. I wasn't saying that he never
heard ATC at all, just that the transmission confusion was due to the
heterodyne, not static or poor transmission quality.

[Mxsmanic]

Emily writes:

> And yes, the official probable cause lists the heterodyne.

No, it does not, at least not if you're thinking of the NTSB reports.
The probable causes are:

- Pilot in command - failed to follow approved procedures, directives,
etc. (KLM)
- Pilot in command - failed to abort takeoff (KLM)

- Personnel - Miscellaneous-personnel: Pilot of other aircraft (Pan
Am)

The first report is DCA77RA014, the second is DCA77RA014. For the KLM
flight, the probable-cause report also lists "Pilot in command -
misunderstanding of orders or instructions" as a factor.

> I thought you would have known that, seeing as you know allegedly
> read all these accident reports.

You can read them yourself with the NTSB IDs above.

--
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[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> And yes, the official probable cause lists the heterodyne.
>
> No, it does not, at least not if you're thinking of the NTSB reports.
> The probable causes are:
>
> - Pilot in command - failed to follow approved procedures, directives,
> etc. (KLM)
> - Pilot in command - failed to abort takeoff (KLM)
>
> - Personnel - Miscellaneous-personnel: Pilot of other aircraft (Pan
> Am)
>
> The first report is DCA77RA014, the second is DCA77RA014. For the KLM
> flight, the probable-cause report also lists "Pilot in command -
> misunderstanding of orders or instructions" as a factor.
>
>> I thought you would have known that, seeing as you know allegedly
>> read all these accident reports.
>
> You can read them yourself with the NTSB IDs above.
>

I wasn't reading the NTSB report.

[Thomas Borchert]

Dan,

> He's got a ton of it to spread around.
>

He must be Skylune ;-)

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

So I guess you can point to the accidents caused by Windows-based glass
cockpits as well as you pointed to sources for accidents caused by AM
radios?


--
Thomas Borchert (EDDH)

[Mxsmanic]

Emily writes:

> He didn't hear ANYTHING but a heterodyne.

Not so. The transmission was hard to make out, but it was not
completely obliterated.

And even if he had heard only that, a squeal is not a take-off
clearance. Either he was deliberately negligent, or he heard
something he wanted to hear.

The actual situation was more complex, but misunderstanding was a key
part of it.

> If you want to say he heard
> the heterodyne as clearance to take off, fine, but that's not what we're
> talking about.

That counts as hearing what you want to hear.

> The OP stated that AM results in poor transmission quality and
> therefore pilots will hear what they want to hear.

Yes. When a transmission is ambiguous, pilots will hear what they
want to hear.

--
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[Mxsmanic]

Emily writes:

> That was my point. He heard what he wanted to hear, but not because of
> jarbled radio transmission.

Only the first part has been established. Nobody knows why he heard
what he wanted to hear; it may or may not have been unintelligible
transmission.

--
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[Mxsmanic]

Emily writes:

> But you just said that all communications are air-ground. You can't
> back pedal.

I can expect others here to have at least a basic knowledge of how
such communications work.

--
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[Mxsmanic]

Emily writes:

> Speaking as someone who works for an OEM that works with the latest
> cutting edge technology, Thomas is entirely correct.

Famous last words again. OEMs that work with cutting-edge technology
are particularly prone to mess up.

--
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[Mxsmanic]

writes:

> There is absolutely no difference in qualilty between AM & FM if they
> are designed to the same specification. If you modulate an AM or FM
> transmitter with up to 3KHx of audio they will sound identical. What
> you put into the transmitter comes out of the receiver assuming there
> isn't a fault.

Not so. The major causes of environmental noise in AM affect the
amplitude of the signal. FM modulates frequency, so changes in
amplitude are not important. Noise that changes frequency is much
more rare in the environment, so FM has less noise. That's the key
advantage of FM.

> FM maintains a low background noise longer than AM and the only
> difference is at low signal levels when FM very quickly becomes
> totally unreadable. AM can still be heard and understood, depending on
> the ability of the person listening. With all the noise in an aircraft
> a little bit of low level background noise is not significant.

With a lot of background noise, additional noise in the channel is
even more of a problem, since the margin of safety is smaller.

> Digital has some merit but again when the signal reaches a threshold
> it stops completely.

But the merit of that is that the transmission is either clean or not
there at all. Errors are rare or nonexistent.

> The whole thread is futile as the centre of the 'aviation universe'
> may well be the US but you aren't going to get the rest of the world
> to change. Even having regultions which are supposed to be accepted
> worldwide doesn't work. Most counties have exceptions.

The world seems to be cooperating pretty well on aviation so far.

> About the only thing which is standard is the use of the English
> language. Even then the locals will use their own language! Have you
> ever worked controllers with Spanish English, Finnish English,
> Canadian English, New Zealand English, Cyprus English, Bahamian,
> Caribbean or even Amereican English. That's where the differences can
> be heard. AM radio is adequate for the job and if you don't think so
> then get your installation checked out by a qualified engineer, you
> may be suprised.

If people are speaking with accents, noise reduction is even more
important, as the redundancy of language is even more reduced.

> As for increasing the number of frequencies Europe has introduced
> 8.3KHz spacing. Fortunately at the lower GA flight levels it's not
> required but the higher commercials now require new radios.
>
> Most radios are dual NAV/COM so not only would you need a new COM but
> a new NAV too... It isn't going to happen...!

So nobody from the USA can fly in Europe now?

--
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[Stefan]

Emily schrieb:

> I think there was some confusion here. I wasn't saying that he never
> heard ATC at all, just that the transmission confusion was due to the
> heterodyne, not static or poor transmission quality.

Ok. And I'm saying that the heterodyne didn't cause anything at all.
More precisely, it caused that the Panam couldn't warn the KLM that they
were still on the runway, which maybe could have prevented the accident
in the last second, agreed. But the fatal misunderstanding occured in
perfect radio conditions and was probably caused by the overall
confusion of the situation (at all participants) and by the desire of
the KLM crew to continue their trip.

Stefan

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> But you just said that all communications are air-ground. You can't
>> back pedal.
>
> I can expect others here to have at least a basic knowledge of how
> such communications work.
>
We do. You don't. All communications are NOT air-ground. Disagree?

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> Speaking as someone who works for an OEM that works with the latest
>> cutting edge technology, Thomas is entirely correct.
>
> Famous last words again. OEMs that work with cutting-edge technology
> are particularly prone to mess up.
>
We haven't yet, in almost 100 years.

[Mxsmanic]

Emily writes:

> I wasn't reading the NTSB report.

It might not hurt to read the reports now, before criticizing anyone
else for not doing research.

--
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[Mxsmanic]

Emily writes:

> I think there was some confusion here. I wasn't saying that he never
> heard ATC at all, just that the transmission confusion was due to the
> heterodyne, not static or poor transmission quality.

But it wasn't. There were multiple transmissions that were
misunderstood, not just the two that were simultaneous.

--
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[Mxsmanic]

Thomas Borchert writes:

> So I guess you can point to the accidents caused by Windows-based glass
> cockpits as well as you pointed to sources for accidents caused by AM
> radios?

Not yet.

As far as I know (and hope), these cockpits don't have any trace of
Windows running in them. If they do, the situation is much more dire
than I had feared.

The problem is that the ergonomy of the systems is shifting towards a
desktop PC model, instead of an aviation model.

--
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[Mxsmanic]

Emily writes:

> All communications are NOT air-ground.

If there is a controller on the channel, they are.

--
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[Mxsmanic]

Emily writes:

> We haven't yet, in almost 100 years.

Cutting-edge technology is relatively new in its current profusion,
and there's always a first time. Will you bet your life on it?

--
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[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> I wasn't reading the NTSB report.
>
> It might not hurt to read the reports now, before criticizing anyone
> else for not doing research.
>
The difference is, I never said I'd read it. YOU did.

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> I think there was some confusion here. I wasn't saying that he never
>> heard ATC at all, just that the transmission confusion was due to the
>> heterodyne, not static or poor transmission quality.
>
> But it wasn't. There were multiple transmissions that were
> misunderstood, not just the two that were simultaneous.
>
Show me the line where it says AM had anything to do with it.

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> All communications are NOT air-ground.
>
> If there is a controller on the channel, they are.
>
That's not what you said before. You're back pedaling, because someone
mentioned CTAF and you realized you were wrong.

[Larry Dighera]

On Sun, 03 Sep 2006 13:39:09 +0200, Mxsmanic >
wrote in >:

>Larry Dighera writes:
>
>> I would guess that noise-blanker and noise-limiting circuits are
>> incorporated in the current radio designs.
>
>You can't actively remove noise over a radio channel because you have
>no unique identifier of noise vs. information.

I believe you'll find Mr. Weir* will take issue with your statement
above.

>> Other than the occasional heterodyne squeal that occurs in the
>> receiver when two transmitters are transmitting on the same frequency
>> simultaneously, there shouldn't be any other noise. Ignition noise
>> should be suppressed by Faraday shielding, and generator/alternator
>> noise should be bypassed to ground.
>
>Anything that isn't signal is noise. AM transmissions are fuzzy and
>hard to hear. In fact, aviation AM radio is probably the noisiest
>type of radio voice communication still in use. Most other types of
>radio communication today are FM.

Where do you get these unsupported statistics?

>> What is the nature of the noise you are hearing? Can you describe it?
>> Is it a hum, pulses, growling, squealing, what?
>
>White noise. It doesn't come from anything within the aircraft or
>station.

Now we're getting somewhere. So that we are all on the same page,
here's a definition of White noise:

http://en.wikipedia.org/wiki/White_noise
[There's an audio sample here also, so you can actually hear it]
White noise is a random signal (or process) with a flat power
spectral density. In other words, the signal's power spectral
density has equal power in any band, at any centre frequency,
having a given bandwidth. White noise is considered analogous to
white light which contains all frequencies.

An infinite-bandwidth white noise signal is purely a theoretical
construct. By having power at all frequencies, the total power of
such a signal is infinite. In practice, a signal can be "white"
with a flat spectrum over a defined frequency band.


http://en.wikipedia.org/wiki/White_noise_machine
A white noise machine is a device that produces a sound that is
random in character, somewhat like air escaping from a balloon.
They generally do not produce actual white noise, which has a
harsh sound, but more often pink noise, whose power rolls off at
higher frequencies, or other colors of noise. They are often used
to protect privacy by masking distant conversations, say in a
psychiatrist's waiting room, and are also sold as sleep aids.

White Noise Machines produces a sound like the gentle whoosh.
Since the sound is absolutely constant but has no structure, the
brain simply tunes it out - just like you have tuned out the noise
from the fans in your computer. You hear the fans, but how often
do you actually notice them?

So, there is a hiss in your receiver when you listen to aviation
communications, and you find it masks intelligibility. Now that you
mention it, I suppose you are correct, because when I turn the Squelch
down, I hear a hiss. The volume of the hiss is much greater when
there is no radio signal present, because the AGC/AVC circuits are
operating at maximum amplification; when a radio signal is present,
that hiss is significantly diminished in volume to the point, that in
36 years of aviation experience, I've never found it an issue.

Perhaps the hiss to which you object is unique to your radio receiving
equipment. How many aviation radios have you had the opportunity to
listen to? Have you found the same objectionable hiss in all aviation
radio receivers you've used?

>> Regardless of when it occurs, there will ultimately be an additional
>> cost.
>
>Sure, but one that companies and individuals can assume on a phased
>basis at their convenience.

So you are proposing that the worldwide aviation community re-equip
all their aircraft and facilities with FM, and that all aviation
stakeholders bear the cost of those conversion, so that you won't hear
a hiss?

Do you really believe that what you propose will pay dividends
commensurate with its cost?

>The fact that transponders and VORs exist today (when they did not in
>the early days of aviation) proves that this works.

In the case of transponders, they were not necessary to operate within
the NAS. Anyone who believes that radio communication is not
necessary to operate within the NAS isn't operating in Class B, C, or
D airspace without prior permission, and the flight mission is not
really meaningful in the sense of accomplishing a meaningful result
like transportation.

In the case of VORs replacing Radio Range and NDBs, those are not
_two-way_ communications, so they are in a different class than
aviation radio communications.

Concurrent operation of differing radio based communication systems is
possible, but to concurrently operate two incompatible aviation
communication systems isn't practicable, because it would require
_all_ air and ground systems to be equipped with both AM and FM
equipment simultaneously and instantly. If not, FM transmissions
would not be received by those stations not equipped with FM
receivers, and vice versa.

For situational awareness, it is vital for all participants to know
what the others in the vicinity are doing by hearing their
instructions and intentions over the radio. For example, when I'm VFR
en route, and hear a military transport "cleared for the approach" to
an airport across whose instrument approach path I'm about to
traverse, although the transmission isn't directed to me, it provides
me with safety information that may be vital to my visually acquiring
conflicting air traffic.

>> You really should read the information at some of the links I provided
>> to get an idea of what has been tried, and what is on the FAA's
>> horizon regarding aviation communications. This topic has been very
>> thoroughly researched by government personnel and it's unlikely that
>> you will hit upon a superior system to what the professionals have
>> examined.
>
>How much of aviation was designed by "professionals"?

You'll find it difficult to find a pilot who regards today's NAS as
armaturely designed. Are you familiar with TERPS?**



* http://www.rst-engr.com/rst/about_us.html#RST%20Engineering


**
http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs420/

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> We haven't yet, in almost 100 years.
>
> Cutting-edge technology is relatively new in its current profusion,
> and there's always a first time. Will you bet your life on it?
>
Since our technology is used on most aircraft I fly on, I already do.

[Larry Dighera]

On Sun, 03 Sep 2006 16:04:01 +0200, Mxsmanic >
wrote in >:

>Larry Dighera writes:
>>>However, you're not supposed to listen to other pilots; you're
>>>supposed to listen to controllers. All conversations are air-ground,
>>>not air-air.
>>
>> You'll have to cite a source for this nugget of knowledge.
>
>FAA AIMs and CFRs make it pretty clear that communications involving a
>controller are pilot-controller exchanges, not pilot-pilot exchanges.

While that may be true, it in no way relates to your statement quoted
above.

Stating "you're not supposed to listen to other pilots" is just plain
wrong. Pilots listen to other pilot transmissions to increase their
situational awareness.

>
>> Are you familiar with Common Traffic Advisory Frequency (CTAF)?
>
>Yes, but it and similar schemes don't involve a controller, so
>obviously the communication is between aircraft directly.

Thank you.

[Larry Dighera]

On Sun, 03 Sep 2006 16:11:09 +0100, wrote in
>:

>FM maintains a low background noise longer than AM and the only
>difference is at low signal levels when FM very quickly becomes
>totally unreadable. AM can still be heard and understood, depending on
>the ability of the person listening. With all the noise in an aircraft
>a little bit of low level background noise is not significant.

Thank you for bringing up this information. I believe it is adequate
to overcome any suggestion of switching from AM to FM for aviation
communications.

[Jim Logajan]

Mxsmanic > wrote:
> Dan Luke writes:
>
>> ******** again. I have a radio that does actively remove noise--it
>> has a button to turn the feature on and off, and it works quite well.
>
> What kind of noise does it remove, and how does it distinguish noise
> from signal?

One proven way to reduce noise is to repeat the signal N times and the
receiver adds up the repetitions and eventually the noise averages to zero
while the signal does not. Of course this is not what is done in practice
in real communications.

(I once wrote software for a Tunneling Electron Microscope (TEM) that did
the above - the target object is repeatedly scanned and the scans are
basically averaged - the noise falls off. Though IIRC, the amplitude of the
noise drops by a factor of 1/sqrt(N) for N scans. I'm too lazy to look it
up so that might not be the correct factor.)

[Mxsmanic]

Emily writes:

> The difference is, I never said I'd read it. YOU did.

A key to progress in debate is knowing what you are talking about.
What you actually say about what you know is irrelevant.

--
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[Mxsmanic]

Emily writes:

> Show me the line where it says AM had anything to do with it.

All of the radio communication was AM.

--
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[Mxsmanic]

Larry Dighera writes:

> I believe you'll find Mr. Weir* will take issue with your statement
> above.

He is welcome to do so.

> So you are proposing that the worldwide aviation community re-equip
> all their aircraft and facilities with FM, and that all aviation
> stakeholders bear the cost of those conversion, so that you won't hear
> a hiss?

I suggest that a less noisy method of communication be found and
implemented, so as to increase safety by improving the reliability of
voice radio communication.

> Do you really believe that what you propose will pay dividends
> commensurate with its cost?

Yes.

> In the case of transponders, they were not necessary to operate within
> the NAS.

At one time, transponders were not needed at all. Then they were. So
obviously things can change.

> In the case of VORs replacing Radio Range and NDBs, those are not
> _two-way_ communications, so they are in a different class than
> aviation radio communications.

They still require new equipment at both ends of the communications
link.

> Concurrent operation of differing radio based communication systems is
> possible, but to concurrently operate two incompatible aviation
> communication systems isn't practicable, because it would require
> _all_ air and ground systems to be equipped with both AM and FM
> equipment simultaneously and instantly.

Why?

> If not, FM transmissions
> would not be received by those stations not equipped with FM
> receivers, and vice versa.

Since everything would be transmitted in both AM and FM by stations
equipped for FM, they would always be receivable by stations equipped
only for AM.

> For situational awareness, it is vital for all participants to know
> what the others in the vicinity are doing by hearing their
> instructions and intentions over the radio.

Which is one reason why things like message queuing are potentially
dangerous.

> For example, when I'm VFR
> en route, and hear a military transport "cleared for the approach" to
> an airport across whose instrument approach path I'm about to
> traverse, although the transmission isn't directed to me, it provides
> me with safety information that may be vital to my visually acquiring
> conflicting air traffic.

You can do even better by flying IFR, but you can also get by with
visual contact only. Every increment in technology ideally provides
an increment in safety, but it's best to avoid designing systems that
increment safety for those who have them but reduce safety for those
who do not.

> You'll find it difficult to find a pilot who regards today's NAS as
> armaturely designed. Are you familiar with TERPS?**

No.

--
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[Thomas Borchert]

Mxsmanic,

> A key to progress in debate is knowing what you are talking about.
> What you actually say about what you know is irrelevant.
>

You're truly a piece of work.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

> All of the radio communication was AM.
>

It was gravity's fault. All the planes were under its influence. No
wait, it was the ocean's fault. All planes were surrounded by it. And
so on...

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

> Not yet.

But you still claimed a risk. You're backpedaling again.

> As far as I know (and hope), these cockpits don't have any trace of
> Windows running in them.

Some do.

> If they do, the situation is much more dire
> than I had feared.

Just because you say so?

> The problem is that the ergonomy of the systems is shifting towards a
> desktop PC model, instead of an aviation model.

The problem is that you obviously haven't the slightest clue what you
are talking about - and that you are completely immune to criticism.
The problem is that you can't show any facts to back up the claims you
make. None. Zip. And that makes it pretty hard to take you even
remotely serious.

--
Thomas Borchert (EDDH)

[Emily[_1_]]

Mxsmanic wrote:
> Emily writes:
>
>> Show me the line where it says AM had anything to do with it.
>
> All of the radio communication was AM.
>
Again, show me the line where the NTSB said that aviation radio being AM
had anything to do with it.

[Mxsmanic]

Thomas Borchert writes:

> Some do.

Which ones?

--
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[Jim Logajan]

Thomas Borchert > wrote:
> Mxsmanic,
>> As far as I know (and hope), these cockpits don't have any trace of
>> Windows running in them.
>
> Some do.

Which ones? (I'd like to know what avionics use MS Windows so I can know
which planes not to get into ;-) )

[Jose[_1_]]

> One proven way to reduce noise is to repeat the signal N times and the
> receiver adds up the repetitions and eventually the noise averages to zero
> while the signal does not. Of course this is not what is done in practice
> in real communications.

Actually, doesn't more transmitter power effectively accomplish that?
(the signal is essentially repeated N times, at the same time)

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Jim Logajan]

Jose > wrote:
>> One proven way to reduce noise is to repeat the signal N times and
>> the receiver adds up the repetitions and eventually the noise
>> averages to zero while the signal does not. Of course this is not
>> what is done in practice in real communications.
>
> Actually, doesn't more transmitter power effectively accomplish that?
> (the signal is essentially repeated N times, at the same time)

The unstated assumption is of course that the transmitter is running at
full power output. Once you've done that, the question is what other tricks
are there to increase the range the signals can be detected.

[Larry Dighera]

On Sun, 03 Sep 2006 21:55:57 +0200, Mxsmanic >
wrote in >:

>Larry Dighera writes:
>
>> So you are proposing that the worldwide aviation community re-equip
>> all their aircraft and facilities with FM, and that all aviation
>> stakeholders bear the cost of those conversion, so that you won't hear
>> a hiss?
>
>I suggest that a less noisy method of communication be found and
>implemented, so as to increase safety by improving the reliability of
>voice radio communication.

You haven't adequately demonstrated the need for a less noisy method
of aviation communications, in my opinion. You allude to NTSB
accident statistics, but you fail to back up your assertions with
actual statistical data. That's pathetically unconvincing.

I'll give you a point for the fact that Mr. Gardner has found a market
for his aviation communication treatise*, but I believe you'll find
that most of the pilots reading this message thread disagree with your
perceived need for less noisy radio receivers. They'll/we'll agree
that _ambient_ noise is a true barrier to intelligibility issue, and I
would guess most pilots have paid for ambient noise canceling headsets
to overcome a true barrier to radio intelligibility. But yours is the
first complaint about white noise present in aviation radio
communications impacting air safety, that I have heard in my 36 years
of being an airman, and I question its validity.

>> Do you really believe that what you propose will pay dividends
>> commensurate with its cost?
>
>Yes.

Can you provide a cost estimate for equipping all ground and air based
communications radios throughout the world? Can you provide a
reasonable analysis of how that enormous sum of money will be repaid
by the increased level of safety it may provide? Frankly, I don't see
the justification for what you propose.
[...]
>
>> For situational awareness, it is vital for all participants to know
>> what the others in the vicinity are doing by hearing their
>> instructions and intentions over the radio.
>
>Which is one reason why things like message queuing are potentially
>dangerous.

Now that is an outright rhetorical dodge. First you said, "All
conversations are air-ground, not air-air," then when I point out you
are incorrect, you change the subject. I'm beginning to find your
lack of sincerity tiring.

>> For example, when I'm VFR
>> en route, and hear a military transport "cleared for the approach" to
>> an airport across whose instrument approach path I'm about to
>> traverse, although the transmission isn't directed to me, it provides
>> me with safety information that may be vital to my visually acquiring
>> conflicting air traffic.
>
>You can do even better by flying IFR, but you can also get by with
>visual contact only. Every increment in technology ideally provides
>an increment in safety, but it's best to avoid designing systems that
>increment safety for those who have them but reduce safety for those
>who do not.

While what you say may be true, it is not an admission that your "All
conversations are air-ground, not air-air." statement was incorrect.
If you're not going to be accountable for what you assert, there is
little reason to continue.

>> You'll find it difficult to find a pilot who regards today's NAS as
>> armaturely designed. Are you familiar with TERPS?**
>
>No.

If you should follow the link I provided in Message-ID:
>, you'll find that they
are the _professionals_ who design the IFR approaches and route
structure.

You seem reasonably bright and to be reasonably well informed about
communications through language, and I admire your perseverance in
promoting your beliefs, but just to make you aware, you are probably
perceived by the pilots reading your articles as someone lacking
firsthand knowledge about aviation communications, someone like an MS
Flight Simulator game player. And your deliberate dodges when pressed
to defend your statements belies someone less than forthright and
sincere.




* http://www.amazon.com/exec/obidos/tg/detail/-/1560275731?v=glance

[Larry Dighera]

On Sun, 03 Sep 2006 22:42:37 -0000, Jim Logajan >
wrote in >:

>Which ones? (I'd like to know what avionics use MS Windows so I can know
>which planes not to get into ;-) )


What's the matter? You're not afraid of the BSOD* on IFR final to
minimums are you? :-)


* http://bsod.org/faqen.php

[Dan Luke]

"Mxsmanic" wrote:

> A key to progress in debate is knowing what you are talking about.

That's done it: you've just blown every irony meter in the newsgroup.

Shame on you. Those things are expensive.

--
Dan

"How can an idiot be a policeman? Answer me that!"
- Chief Inspector Dreyfus

[Peter R.]

Jim Logajan > wrote:

> Which ones? (I'd like to know what avionics use MS Windows so I can know
> which planes not to get into ;-) )

The Apollo/Garmin MX20 is powered by Windows NT. I have had two "BSODs" in
the three years I have been behind the unit, and both were related to the
WSI downlinked weather being displayed on the unit.


--
Peter

[Emily[_1_]]

Larry Dighera wrote:
> On Sun, 03 Sep 2006 22:42:37 -0000, Jim Logajan >
> wrote in >:
>
>> Which ones? (I'd like to know what avionics use MS Windows so I can know
>> which planes not to get into ;-) )
>
>
> What's the matter? You're not afraid of the BSOD* on IFR final to
> minimums are you? :-)
>
>
> * http://bsod.org/faqen.php

You just made my blood run cold. Can you even imagine? lol

[Morgans[_4_]]

"Mxsmanic" > wrote
>
> If there is a controller on the channel, they are.

The first rule of digging your way out of a deep hole, is to first stop
digging.

Give it up.
--
Jim in NC

[Morgans[_4_]]

"Vaughn Simon" > wrote

> Such as VOIP actually, or other digital technologies that are now
quite
> common, cheap, and "off the shelf". In police and fire communications, FM
is
> quickly giving away to digital modes. My bad for previously talking about
FM as
> if it were the only possibility.

And your strategy for implementing such a new system, besides requiring
everyone to replace their radios is......?

Even if you got everyone to agree, and pay the money for the new equipment,
the electronics industry could not supply the necessary hardware, except
over a period of a couple years, minimum. In the meantime, we all use
what......?
--
Jim in NC

[Morgans[_4_]]

> > He's got a ton of it to spread around.
> >
>
> He must be Skylune ;-)

I think it is finally time to cut my losses with Mxsmanic, and toss him into
the kill file. His/her posts are close to half tonight's total posting
volume, and ALL they are is pure BS.

I really have better things to do with my time. I bet everyone does.

I would hope to see most agree on this subject, and not respond to his/her
posts, so we that wish to see the BS no longer, don't have to see the BS in
someone's replies, again.

Wishful thinking, anyway. <g>
--
Jim in NC

[Jose[_1_]]

I suspect that the (incorrect) sense that FM is better than AM comes
from broadcast stations. I think broadcast FM uses more channel space
than broadcast AM, and it is =that= which gives higher fidelity, for the
most part.

Don't be fooled. It's the bandwidth, not the encoding.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Thomas Borchert]

Morgans,

> I would hope to see most agree on this subject, and not respond to his/her
> posts, so we that wish to see the BS no longer, don't have to see the BS in
> someone's replies, again.
>

Oh come on, it's so much fun to jerk the chains of these people ;-)

--
Thomas Borchert (EDDH)

[Mxsmanic]

Peter R. writes:

> The Apollo/Garmin MX20 is powered by Windows NT. I have had two "BSODs" in
> the three years I have been behind the unit, and both were related to the
> WSI downlinked weather being displayed on the unit.

That is worrisome.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Jose writes:

> Don't be fooled. It's the bandwidth, not the encoding.

It's the encoding. Most interference plays with amplitude, not
frequency.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Jose writes:

> Actually, doesn't more transmitter power effectively accomplish that?
> (the signal is essentially repeated N times, at the same time)

Yes.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Larry Dighera writes:

> You haven't adequately demonstrated the need for a less noisy method
> of aviation communications, in my opinion.

I'm not trying to demonstrate need, I'm trying to demonstrate
desirability.

> But yours is the
> first complaint about white noise present in aviation radio
> communications impacting air safety, that I have heard in my 36 years
> of being an airman, and I question its validity.

It's not just white noise; it's the poor quality of audio generally.

Would you buy a book on tape or CD with the same audio quality as
aviation radio communications? If not, why not?

> Can you provide a cost estimate for equipping all ground and air based
> communications radios throughout the world?

No. But it's a gradual process, so there is no single huge
expenditure. And it isn't all paid for by the same entity.

> Can you provide a
> reasonable analysis of how that enormous sum of money will be repaid
> by the increased level of safety it may provide? Frankly, I don't see
> the justification for what you propose.

It's hard to put a price on safety. Some people care a lot about it,
some people care very little about it.

The only reason aviation is at all safe in the first place is that a
lot of people spend a lot of money to make it that way. They do so
without necessarily being able to put a dollar value on the safety
they gain.

> You seem reasonably bright and to be reasonably well informed about
> communications through language, and I admire your perseverance in
> promoting your beliefs, but just to make you aware, you are probably
> perceived by the pilots reading your articles as someone lacking
> firsthand knowledge about aviation communications, someone like an MS
> Flight Simulator game player.

So? I expect my discussions to be judged on their own merits, not on
subjective opinions formed about me personally by others. Anyone who
depends on the latter won't be able to hold an interesting discussion,
anyway.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[[email protected]]

On Mon, 04 Sep 2006 09:37:53 +0200, Mxsmanic >
wrote:

>Larry Dighera writes:
>
>> You haven't adequately demonstrated the need for a less noisy method
>> of aviation communications, in my opinion.
>
>I'm not trying to demonstrate need, I'm trying to demonstrate
>desirability.
>
>> But yours is the
>> first complaint about white noise present in aviation radio
>> communications impacting air safety, that I have heard in my 36 years
>> of being an airman, and I question its validity.
>
>It's not just white noise; it's the poor quality of audio generally.
>

You don't seem to understand there is NO quality difference in audio
quality between FM & AM, unless you're equipment is faulty and
introducing distortion. I've used AM & FM with amateur radio and been
a professional Broadcast Engineer for 30 years so believe me you are
wrong!

If you compare "like for like" they are both clear and almost
identical quality under normal signal levels. It's only when they
become weak that AM slowly degrades, soon after that point FM will
just stop working.

Don't compare broadcast quality FM with AM. Broadcast FM uses about
15KHz audio bandwidth and likely to be 50KHz or 75KHz deviation, that
gives a channel width of about 130KHz or 180KHz wide (if I remember
correctly) that's why you get low noise in the system. Compare this to
communication quality FM which is likely to have only about 3 to 5KHz
deviation and you'll see a large difference. The bandwidth used is
then much less, but still wider than AM. As I've previously stated an
AM transmitter with 3KHz audio bandwidth has an RF bandwidth of only
6KHz. An FM transmitter using only 6KHz bandwidth will not work as
well as you seem to imply and it requires a wider channel width unless
you reduce the deviation even more and sacrifice the benefits of FM..

Even commercial broadcast AM only uses a narrow audio bandwidth. I'm
not sure but I believe the audio bandwidth of AM broadcast is about
6KHz. On top of that many use very sophisticated audio compressors
which increase the audio level drastically so everything sounds
louder. It means the transmitters are almost fully modulated most of
the time which gives good signal to noise ratio. That helps when
listening in high noise environments like a car. You loose the dynamic
range and distort the signal but it improves readability. Broadcast FM
also uses compression but not as much so less distortion. Classical
radio stations want to retain the dynamic range so should not use
compression.

- snip-

>It's hard to put a price on safety. Some people care a lot about it,
>some people care very little about it.
>

Safety is not all about using radios. I've had a transmitter audio
failure within a military controlled area. It was a non-event. Simply
squawked 7600 listened on the receiver and replied with mike clicks.
Got an IFR clearance (even in VFR) and landed with the green lights.

Like others have said this is going nowhere and there are too many
unsupported facts and misunderstandings. If you're a pilot you'll know
AM works well.

[Vaughn Simon]

"Morgans" > wrote in message
...
>
> Even if you got everyone to agree, and pay the money for the new equipment,
> the electronics industry could not supply the necessary hardware, except
> over a period of a couple years, minimum. In the meantime, we all use
> what......?

It would have to be done with dual mode radios, in the same manner that the
cell phone industry made the move from analog to digital and in the manner that
the TV broadcast industry is making that same switch today. Yes, everybody
would have to buy a new radio over a period of just a few years, which is
exactly why I don't expect to live long enough to see it happen.

Vaughn in FL


> --
> Jim in NC
>

[Vaughn Simon]

"Thomas Borchert" > wrote in message
...
>>
>
> Oh come on, it's so much fun to jerk the chains of these people ;-)

Yes, but it is important for you to stop and consider; who is the jerker
and who is the jerk? Once you clearly understand, you will stop responding to
trolls.

Vaughn

[Dylan Smith]

On 2006-09-02, Mxsmanic > wrote:
> The reason I ask is that improper and misunderstood radio
> communication is a leading cause of accidents, and so it seems that

If you look at the NTSB reports, you'll find that this is not so - in
fact, accidents caused by bad radio communications are so rare, they
barely register as statistical noise! For each accident caused by poor
communication, there are probably thousands of accidents caused by a
pilot flying into weather they cannot handle.

Aircraft fly on the principles of Bernoulli and Newton, not Marconi, and
will fly quite happily with no radio at all, so long as the pilot
remembers to look out of the window and not bang into anything.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Dylan Smith]

On 2006-09-03, Mxsmanic > wrote:
> However, you're not supposed to listen to other pilots; you're
> supposed to listen to controllers. All conversations are air-ground,
> not air-air.

Err... whiskey-tango-foxtrot!?

Of course you're supposed to listen to other pilots. Even when IFR, you
get a picture of what and where the other traffic is so you can think
ahead and anticipate what sort of clearance you're going to get, say,
when entering the terminal area.

Others have pointed out the CTAF so I won't labour that point.
Air-to-air communications is a matter of course, and very useful.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Dylan Smith]

On 2006-09-03, Mxsmanic > wrote:
> Emily writes:
>
>> All communications are NOT air-ground.
>
> If there is a controller on the channel, they are.

That's incorrect, too. During a formation flight, there will be some
communication between the formation members even when ATC is involved.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Dylan Smith]

On 2006-09-03, Mxsmanic > wrote:
> I doubt that they are using VoIP, though, which is notoriously
> unreliable.

You're confusing VOIP (voice carried on top of IP packets), which is as
reliable as any other internet protocol with the reliability of a data
stream over the general Internet (note: capital I). VOIP itself is no
less reliable than any other data transmission.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Thomas Borchert]

Mxsmanic,

> It's hard to put a price on safety.
>

You are making the second step after the first. You still haven't shown
how the use of AM radios influences safety. If there is no connection
between AM and safety (and you have shown zero evidence that there is,
even when asked to show it), then it can't possibly enhance safety. So
we're really discussing the price of radios, not of safety.

--
Thomas Borchert (EDDH)

[Dylan Smith]

On 2006-09-03, Mxsmanic > wrote:
> As far as I know (and hope), these cockpits don't have any trace of
> Windows running in them. If they do, the situation is much more dire
> than I had feared.

I've seen general aviation displays that run Windows NT. They don't have
the Win32 subsystem (which is what really sullies the NT based operating
systems, the actual NT kernel that lies beneath things like the win32
subsystem is quite small and elegant).

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Dylan Smith]

On 2006-09-03, Jim Logajan > wrote:
> Which ones? (I'd like to know what avionics use MS Windows so I can know
> which planes not to get into ;-) )

I recently saw a photograph of the flight deck of the Airbus A380.
Inside, one on the captain's side and one on the FO's side is a pull out
keyboard and display, the display was clearly showing a Windows start
menu. I doubt the PC had anything to do with _flying_ the plane itself -
it was probably a general purpose information system that could be used
in flight. However, it would be amusing if someone loads up Flight
Simulator on the A380 flight deck PCs :-) Or even more amusing, if they
load up Flight Simulator on the flight deck PCs on the Airbus A380
simulator :-)

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Bob Noel]

In article >,
Dylan Smith > wrote:

> I've seen general aviation displays that run Windows NT. They don't have
> the Win32 subsystem (which is what really sullies the NT based operating
> systems, the actual NT kernel that lies beneath things like the win32
> subsystem is quite small and elegant).

Do any of those displays have the software at DO-178B Level C or higher?
(btw - I do know a little about the avidyne display)

--
Bob Noel
Looking for a sig the
lawyers will hate

[Dave Stadt]

"Mxsmanic" > wrote in message
...
> Thomas Borchert writes:
>
>> So I guess you can point to the accidents caused by Windows-based glass
>> cockpits as well as you pointed to sources for accidents caused by AM
>> radios?
>
> Not yet.
>
> As far as I know (and hope), these cockpits don't have any trace of
> Windows running in them. If they do, the situation is much more dire
> than I had feared.

You neeed to look a litle closer.

[Dave Stadt]

"Mxsmanic" > wrote in message
...
> Dave Stadt writes:
>
>> Nope, it was quite a ways down the line. Morse code via spark gap
>> transmitters was one of the first.
>
> All early audio used AM.

Yea, so.

[Emily[_1_]]

Thomas Borchert wrote:
> Mxsmanic,
>
>> It's hard to put a price on safety.
>>
>
> You are making the second step after the first. You still haven't shown
> how the use of AM radios influences safety. If there is no connection
> between AM and safety (and you have shown zero evidence that there is,
> even when asked to show it), then it can't possibly enhance safety. So
> we're really discussing the price of radios, not of safety.
>
And actually, the FAA and NTSB DO put a price on safety.

But why introduce logic at this point?

[Thomas Borchert]

Dylan,

> accidents caused by bad radio communications are so rare, they
> barely register as statistical noise!
>

Ah, but if it weren't for AM, that noise would be so much less ;-)

--
Thomas Borchert (EDDH)

[Larry Dighera]

On Mon, 04 Sep 2006 08:41:34 -0400, Bob Noel
> wrote in
>:

>Do any of those displays have the software at DO-178B Level C or higher?
>(btw - I do know a little about the avidyne display)

I am very apprehensive about Avidyne avionics. What can you say about
their products?

[Bob Noel]

In article >,
Larry Dighera > wrote:

> >Do any of those displays have the software at DO-178B Level C or higher?
> >(btw - I do know a little about the avidyne display)
>
> I am very apprehensive about Avidyne avionics. What can you say about
> their products?

I don't have any in my 140, but then, I don't even have any GPS whatsoever.
This is more a reflection of not needing to upgrade a good 1995 panel than
a reflection on Avidyne.

I can say that Avidyne was the first company to get a windows-based product
certified to a 178B level that would ordinarily be level C. Note that the
windows portion of the software does NOT comply with Level C objectives.
But last I knew, Avidyne consider the technique(s) used to be proprietary.
(I don't what they are, but I have some educated guesses on possible methods).

I've seen some demos of their products, which look way cool, but they are
also way too expensive for me.

Not much help - I know...

--
Bob Noel
Looking for a sig the
lawyers will hate

[Larry Dighera]

On Mon, 04 Sep 2006 11:29:17 -0400, Bob Noel
> wrote in
>:

>In article >,
> Larry Dighera > wrote:
>
>> >Do any of those displays have the software at DO-178B Level C or higher?
>> >(btw - I do know a little about the avidyne display)
>>
>> I am very apprehensive about Avidyne avionics. What can you say about
>> their products?
>

>I can say that Avidyne was the first company to get a windows-based product
>certified to a 178B level that would ordinarily be level C.

Just so we are all aware of the definition of DO-178B software levels:

http://en.wikipedia.org/wiki/DO-178B
Software level
-------------

The required level is determined from the safety assessment
process and hazard analysis by examining the effects of a failure
condition in the system. The failure conditions are categorized by
their effects on the aircraft, crew, and passengers.

Catastrophic [Level A] - Failure may cause a crash.

Hazardous [Level B] - Failure has a large negative impact on
safety or performance, or reduces the ability of the crew to
operate the plane due to physical distress or a higher workload,
or causes serious or fatal injuries among the passengers.

Major [Level C] - Failure is significant, but has a lesser impact
that a Hazardous failure (for example, leads to passenger
discomfort rather than injuries).

Minor [Level D] - Failure is noticeable, but has a lesser impact
than a Major failure (for example, causing passenger inconvenience
or a routine flight plan change)

No Effect [Level E] - Failure has no impact on safety, aircraft
operation, or crew workload.

The number of objectives to be satisfied (with independence) is
determined by the software level.

Level Failure condition Objectives With independence
----------------------------------------------------------
A Catastrophic 66 25
B Hazardous 65 14
C Major 57 2
D Minor 28 2
E No effect 0 0


>Note that the windows portion of the software does NOT comply with
>Level C objectives.

I presume that Windows does not comply with Level B either.

And how, pray tell, can avionics that run an OS incapable of meeting
the specification be citified to it?

>But last I knew, Avidyne consider the technique(s) used [to meet DO-178B] to be
>proprietary. (I don't [know] what they are, but I have some educated guesses
>on possible methods).

Would those methods include mordita?*

>I've seen some demos of their products, which look way cool, but they are
>also way too expensive for me.

But are Avidyne products that employ Windows OS reliable enough to
preclude their negatively impacting air safety?

>Not much help - I know...

You know more about the subject than me. Thanks for your input.


* http://www.sandiegomag.com/forums/aviation/cptnmord.shtml

[Bob Noel]

In article >,
Larry Dighera > wrote:

>Just so we are all aware of the definition of DO-178B software levels:
> Catastrophic [Level A] - Failure may cause a crash.

"Failure conditions which would prevent continued safe flight and
landing."

> Hazardous [Level B] - Failure has a large negative impact on
> safety or performance, or reduces the ability of the crew to
> operate the plane due to physical distress or a higher workload,
> or causes serious or fatal injuries among the passengers.

"Failure conditions which would reduce the capability of the aircraft or the
ability of the crew to cope with adverse operating conditions to the extent that
there would be:

(1) a large reduction in safety margins or functional capabilities,

(2) physical distress or higher workload such that the flight crew could not be
relied on to perform their tasks accurately or completely, or

(3) adverse effects on occupants including serious or potentially fatal injuries
to a small number of those occupants."


>
> Major [Level C] - Failure is significant, but has a lesser impact
> that a Hazardous failure (for example, leads to passenger
> discomfort rather than injuries).

"Failure conditions which would reduce the capability of the aircraft or the
ability of the crew to cope with adverse operating conditions to the extent that
there would be, for example, a significant reduction in safety margins or
functional capabilities, a significant increase in crew workload or in
conditions impairing crew efficiency, or discomfort to occupants, possibly
including injuries."

>
> Minor [Level D] - Failure is noticeable, but has a lesser impact
> than a Major failure (for example, causing passenger inconvenience
> or a routine flight plan change)

"Failure conditions which would not significantly reduce aircraft safety, and
which would involve crew actions that are well within their capabilities. Minor
failure conditions may include, for example, a slight reduction in safety
margins or functional capabilities, a slight increase in crew workload, such as,
routine flight plan changes, or some inconvenience to occupants."

>
> No Effect [Level E] - Failure has no impact on safety, aircraft
> operation, or crew workload.

"Failure conditions which do not affect the operational capability of the
aircraft or increase crew workload."


[snip]
> >Note that the windows portion of the software does NOT comply with
> >Level C objectives.
>
> I presume that Windows does not comply with Level B either.

Correct.

>
> And how, pray tell, can avionics that run an OS incapable of meeting
> the specification be citified to it?

By otherwise mitigating or controlling the hazard. For example, there could
be some other portion of the system (e.g., hardware) that is independently
monitoring the windows-based application.



>
> >But last I knew, Avidyne consider the technique(s) used [to meet DO-178B] to
> >be
> >proprietary. (I don't [know] what they are, but I have some educated
> >guesses
> >on possible methods).
>
> Would those methods include mordita?*

If I understand the reference correctly, no.


> >I've seen some demos of their products, which look way cool, but they are
> >also way too expensive for me.
>
> But are Avidyne products that employ Windows OS reliable enough to
> preclude their negatively impacting air safety?

I don't believe that their PFDs include windows. I assume that they have
some form of Greenhill's RTOS or Windriver's OS.

The stuff with Windows is just for situational awareness, they don't perform
any functions required for safe flight.

--
Bob Noel
Looking for a sig the
lawyers will hate

[Mxsmanic]

Dylan Smith writes:

> That's incorrect, too. During a formation flight, there will be some
> communication between the formation members even when ATC is involved.

Are there a lot of GA and commercial formation flights in the air?

That's a bit like saying that smoking flying out of the back of an
aircraft should not necessarily be considered abnormal because a few
acrobatic flying teams use it.

--
Transpose mxsmanic and gmail to reach me by e-mail.

[Mxsmanic]

Dylan Smith writes:

> I recently saw a photograph of the flight deck of the Airbus A380.
> Inside, one on the captain's side and one on the FO's side is a pull out
> keyboard and display, the display was clearly showing a Windows start
> menu. I doubt the PC had anything to do with _flying_ the plane itself ...

I certainly hope it doesn't. But knowing Airbus, and its tendency to
install bleeding-edge gadgets on its aircraft in a desperate attempt
to have _something_ that Boeing does not, it wouldn't surprise me at
all if Windows were being used for safety-of-life applications (even
though Microsoft itself recommends against this in the strongest
terms).

> ... it was probably a general purpose information system that could be used
> in flight.

I should think that pilots would have better things to do than type on
a PC. There's enough to worry about in commercial aviation as it is.

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[Mxsmanic]

Dylan Smith writes:

> I've seen general aviation displays that run Windows NT. They don't have
> the Win32 subsystem (which is what really sullies the NT based operating
> systems, the actual NT kernel that lies beneath things like the win32
> subsystem is quite small and elegant).

Which displays? If it's for safety-of-life applications, it's an
extremely stupid and dangerous idea to use Windows NT.

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[Mxsmanic]

Dave Stadt writes:

> You neeed to look a litle closer.

Looking closer might be scary, if I find Windows behind any
mission-critical systems.

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[Mxsmanic]

writes:

> You don't seem to understand there is NO quality difference in audio
> quality between FM & AM, unless you're equipment is faulty and
> introducing distortion. I've used AM & FM with amateur radio and been
> a professional Broadcast Engineer for 30 years so believe me you are
> wrong!

Odd that FM seems to sweep AM out of so many markets, then. All the
FM transmissions I've heard were superior to AM.

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[Mxsmanic]

Larry Dighera writes:

> But are Avidyne products that employ Windows OS reliable enough to
> preclude their negatively impacting air safety?

Nothing that runs a Windows OS is suitable for safety-of-life
applications. This is no reflection on Windows; it's just that the
operating system is designed for general information processing use in
homes, offices, and schools ... not for process control, real-time
systems, or mission-critical applications.

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[Mxsmanic]

Larry Dighera writes:

> The required level is determined from the safety assessment
> process and hazard analysis by examining the effects of a failure
> condition in the system.

In other words, nobody actually examines or formally verifies the
code.

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[Jim Logajan]

Mxsmanic > wrote:
> writes:
>
>> You don't seem to understand there is NO quality difference in audio
>> quality between FM & AM, unless you're equipment is faulty and
>> introducing distortion. I've used AM & FM with amateur radio and been
>> a professional Broadcast Engineer for 30 years so believe me you are
>> wrong!
>
> Odd that FM seems to sweep AM out of so many markets, then. All the
> FM transmissions I've heard were superior to AM.

I believe FM's principle advantage over AM is superior immunity to certain
classes of noise - audio fidelity per se should be equal. Here's what my
copy of "The ARRL Handbook for Radio Amateurs, 2002" says about FM:

"The primary advantage of FM is its ability to produce a high signal-to-
noise ratio when receiving a signal of only moderare strength. This has
made FM popular for mobile communications services and high-quality
broadcasting. However, because of the wide bandwidth required and the
distortion suffered in skywave propagation, the use of FM has generally
been limited to frequencies higher than 29 MHz."

[Jose[_1_]]

Mxsmanic > wrote:
>> Odd that FM seems to sweep AM out of so many markets, then. All the
>> FM transmissions I've heard were superior to AM.

That's the reason for your error. You are relying on your experience
with broadcast radio, without compensating for other differences.

Broadcast FM has huge bandwidth. (look it up - don't just take it from me)

Broadcast AM has tiny bandwidth. (look that up too)

It is the bandwidth difference that makes broadcast FM look better than
broadcast AM, not the encoding difference.

Think of it this way - they make concrete highways and dirt roads.
Station wagons are allowed only on dirt roads, sedans are allowed only
on concrete highways. I can get from NY to CA much faster in a sedan.

Are sedans inherenly faster?

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[Dylan Smith]

On 2006-09-04, Mxsmanic > wrote:
> Dylan Smith writes:
>
>> That's incorrect, too. During a formation flight, there will be some
>> communication between the formation members even when ATC is involved.
>
> Are there a lot of GA and commercial formation flights in the air?

That's irrelevant - your assertion was that if there was a controller on
frequency, then pilots only talk to the controller and there is no air
to air communications. This is false, even if there is only ever one
formation flight a year. (In reality, GA formation flight isn't that
uncommon, I've participated in dozens of GA formation flights, many of
which involved communication with ATC, as well as formation takeoffs
from controlled fields).

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[[email protected]]

On Mon, 04 Sep 2006 17:59:41 -0000, Jim Logajan >
wrote:

>Mxsmanic > wrote:
>> writes:
>>
>>> You don't seem to understand there is NO quality difference in audio
>>> quality between FM & AM, unless you're equipment is faulty and
>>> introducing distortion. I've used AM & FM with amateur radio and been
>>> a professional Broadcast Engineer for 30 years so believe me you are
>>> wrong!
>>
>> Odd that FM seems to sweep AM out of so many markets, then. All the
>> FM transmissions I've heard were superior to AM.
>
>I believe FM's principle advantage over AM is superior immunity to certain
>classes of noise - audio fidelity per se should be equal. Here's what my
>copy of "The ARRL Handbook for Radio Amateurs, 2002" says about FM:
>
>"The primary advantage of FM is its ability to produce a high signal-to-
>noise ratio when receiving a signal of only moderare strength. This has
>made FM popular for mobile communications services and high-quality
>broadcasting. However, because of the wide bandwidth required and the
>distortion suffered in skywave propagation, the use of FM has generally
>been limited to frequencies higher than 29 MHz."

Yes you're correct "audio fidelity per se should be equal" but you
also mention bandwidth, that's critical. There are some advantages
with FM, until the signal gets weak! The other reason for FM is you
can easily modulate the carrier at low level. With AM you need a
higher power modualtor which uses more power.

[[email protected]]

On Mon, 04 Sep 2006 19:47:13 +0200, Mxsmanic >
wrote:

writes:
>
>> You don't seem to understand there is NO quality difference in audio
>> quality between FM & AM, unless you're equipment is faulty and
>> introducing distortion. I've used AM & FM with amateur radio and been
>> a professional Broadcast Engineer for 30 years so believe me you are
>> wrong!
>
>Odd that FM seems to sweep AM out of so many markets, then. All the
>FM transmissions I've heard were superior to AM.

Because it's simple to modulate at low level and generally uses a
wider bandwidth. It is only superior in signal to noise as long as the
receiver detector is limiting but once the signal drops it's useless.
I don't know if you would get much multipath distortion from the
ground to an aircraft but if you do you would get noticable
distortion.

I cannot remember the exact figures but I seem to remember
communication quality AM is about 8db better than the equivalent FM.
SSB is about 13db better than FM. Remember you need also to specify
power.

[[email protected]]

On Mon, 04 Sep 2006 18:15:29 GMT, Jose >
wrote:

>Mxsmanic > wrote:
>>> Odd that FM seems to sweep AM out of so many markets, then. All the
>>> FM transmissions I've heard were superior to AM.
>
>That's the reason for your error. You are relying on your experience
>with broadcast radio, without compensating for other differences.
>
Yes, thank you for understanding that!

>Broadcast FM has huge bandwidth. (look it up - don't just take it from me)
>
>Broadcast AM has tiny bandwidth. (look that up too)
>
>It is the bandwidth difference that makes broadcast FM look better than
>broadcast AM, not the encoding difference.
>
>Think of it this way - they make concrete highways and dirt roads.
>Station wagons are allowed only on dirt roads, sedans are allowed only
>on concrete highways. I can get from NY to CA much faster in a sedan.
>
>Are sedans inherenly faster?
>
>Jose

At this point I'll give up with the troll but I hope those of you who
are pilots heave learned something useful.

[RK Henry]

On Tue, 05 Sep 2006 00:49:23 +0100, wrote:

>I cannot remember the exact figures but I seem to remember
>communication quality AM is about 8db better than the equivalent FM.
>SSB is about 13db better than FM. Remember you need also to specify
>power.

I think you have identified precisely the reason why aircraft use AM,
or in some cases SSB, instead of FM. We're going for distance, not
quality. Voice's narrow range of frequencies doesn't require broadband
to useful information. Under many circumstances, punching through with
a noisy, barely readable message is preferable to no message at all.
Flying an ordinary instrument approach might exceed the limits of
narrowband FM, especially if the aircraft happens to be encased in
ice. Over mountains, it's easy to exceed the limits of VHF
communications with ATC, getting a weak, "radar service terminated..."
until you get closer to the airport or to a RCO. I don't think we're
willing to go to the extreme of SSB, so AM offers a reasonable
compromise for most operations.

On the issue of intelligibility, I've always found that a more
important factor is equipment, not modulation. Old, decrepit
radios in need of maintenance send and receive poorly. I've flown
airplanes where one radio was loud and clear and the other was
unreadable. Bad microphones may not give the transmitter much to work
with either. There are still airplanes flying with cheap (relatively)
carbon hand mikes. I was flying with such a mike, from a major name in
aircraft communications, when ATC refused to handle my flight because
of the poor communications. Some headset mikes can be really bad too.
Some aren't even noise canceling, and sometimes even noise canceling
isn't enough, as evidenced by some transmissions I've heard from
helicopters. It should also be noted that communication mikes have a
different frequency response from the broadcast mikes they use at the
FM broadcast station. The frequency response helps to emphasize those
frequencies that will punch the signal out over a distance.

A good AM radio with a good mike ought to give quite satisfactory
results. Unfortunately, sometimes FAA's radios aren't that good
either. I once reported poor transmissions to a controller. He thanked
me, made a switch, and I was then able to report 5x5 to him. Unicom
operators' radios are sometimes virtually useless.

RK Henry

[Thomas Borchert]

Mxsmanic,

> But knowing Airbus, and its tendency to
> install bleeding-edge gadgets on its aircraft in a desperate attempt
> to have _something_ that Boeing does not,

Examples?

> There's enough to worry about in commercial aviation as it is.

Examples?

Oh, I forgot, you don't back up your "statements" with fact.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

> This is no reflection on Windows; it's just that the
> operating system is designed for general information processing use in
> homes, offices, and schools ... not for process control, real-time
> systems, or mission-critical applications.
>

Says who? You?

--
Thomas Borchert (EDDH)

[[email protected]]

On Tue, 05 Sep 2006 06:34:33 GMT, RK Henry
> wrote:

>On Tue, 05 Sep 2006 00:49:23 +0100, wrote:
>
>>I cannot remember the exact figures but I seem to remember
>>communication quality AM is about 8db better than the equivalent FM.
>>SSB is about 13db better than FM. Remember you need also to specify
>>power.
>
>I think you have identified precisely the reason why aircraft use AM,
>or in some cases SSB, instead of FM. We're going for distance, not
>quality. Voice's narrow range of frequencies doesn't require broadband
>to useful information. Under many circumstances, punching through with
>a noisy, barely readable message is preferable to no message at all.
>Flying an ordinary instrument approach might exceed the limits of
>narrowband FM, especially if the aircraft happens to be encased in
>ice. Over mountains, it's easy to exceed the limits of VHF
>communications with ATC, getting a weak, "radar service terminated..."
>until you get closer to the airport or to a RCO. I don't think we're
>willing to go to the extreme of SSB, so AM offers a reasonable
>compromise for most operations.
>
>On the issue of intelligibility, I've always found that a more
>important factor is equipment, not modulation. Old, decrepit
>radios in need of maintenance send and receive poorly. I've flown
>airplanes where one radio was loud and clear and the other was
>unreadable. Bad microphones may not give the transmitter much to work
>with either. There are still airplanes flying with cheap (relatively)
>carbon hand mikes. I was flying with such a mike, from a major name in
>aircraft communications, when ATC refused to handle my flight because
>of the poor communications. Some headset mikes can be really bad too.
>Some aren't even noise canceling, and sometimes even noise canceling
>isn't enough, as evidenced by some transmissions I've heard from
>helicopters. It should also be noted that communication mikes have a
>different frequency response from the broadcast mikes they use at the
>FM broadcast station. The frequency response helps to emphasize those
>frequencies that will punch the signal out over a distance.
>
>A good AM radio with a good mike ought to give quite satisfactory
>results. Unfortunately, sometimes FAA's radios aren't that good
>either. I once reported poor transmissions to a controller. He thanked
>me, made a switch, and I was then able to report 5x5 to him. Unicom
>operators' radios are sometimes virtually useless.
>
>RK Henry

Thank you RKH, I wasn't going return to this thread but you have
detailed exactly what I was trying to put across.

SSB is by far the best for long range communication but requires very
accurate tuning, unless you leave a small amount of carrier and allow
the receiver to do it for you. At least with AM the carrier is
transmitted along with the signal so tuning is relatively unimportant.
You only have to listen to two stations transmitting at the same time
and you can hear the inaccuracy in the form of the heterodyne. If they
were both on frequency you would not hear the hetrodine.

David

[jladd]

FM receivers typically use a PLL (phase lock loop) circuit for
demodulation. In the presence of multiple received signals the largest
amplitude one will be locked to and thus demodulated. In AM receivers
all signals present at the detector above a certain noise threshhold
are detected. This feature, while often noiser, allows your friendly
controller to hear two guys calling simultaneously. For voice
transmissions, narrow band FM can be used and equivalent bandwidth
results.

Sorry if this is addressed somewhere in this thread already. I didn't
wade through all of it.

[Mxsmanic]

Thomas Borchert writes:

> Says who? You?

I and Microsoft, as well as anyone else familiar with Windows
internals.

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[Thomas Borchert]

Mxsmanic,

> I and Microsoft, as well as anyone else familiar with Windows
> internals.
>

Sources? (I'll be really interesetd in one for the "anyone else" part)

Windows isn't Windows, as you try to make it in your generalization -
which in itslef implies a certain cluelessness with the topic.
Furthermore, these units are certified to certain reliability levels,
which are well defined. Your sweepingly broad statements just aren't
true.

--
Thomas Borchert (EDDH)

[Bob Noel]

In article >,
Thomas Borchert > wrote:

> Sources? (I'll be really interesetd in one for the "anyone else" part)
>
> Windows isn't Windows, as you try to make it in your generalization -
> which in itslef implies a certain cluelessness with the topic.
> Furthermore, these units are certified to certain reliability levels,
> which are well defined. Your sweepingly broad statements just aren't
> true.

What reliability levels are available for which windows products that would
be appropriate for a critical application? I assume you aren't talking about
Windows XP versions intended for desktop/laptop computers.

I wasn't aware that microsoft had any OS that would "certifiable" to DO-178B
level C or above (for those that are familar with 178B, please forgive the
shorthand wrt certification and levels), never mind any of the European
safety standards.

--
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Looking for a sig the
lawyers will hate

[Grumman-581[_3_]]

"Steven P. McNicoll" > wrote in message
ink.net...
> Didn't all early radio use AM?

Technically, they were probably digital... Dashes and dots... <grin>

.-.. .. ...- . / ..-. .- ... -
-.. .. . / -.-- --- ..- -. --.
.-.. . .- ...- . / .- / -.-. ..- - . / .-- .. -.. --- .--

----
--. .-. ..- -- -- .- -. ..... ---.. .---- .--.-. --. -- .- .. .-..
..-.-.- -.-. --- --

[Grumman-581[_3_]]

"Jim Logajan" > wrote in message
.. .
> Which ones? (I'd like to know what avionics use MS Windows so I can know
> which planes not to get into ;-) )

There are some aircraft systems that use an embedded version of XP and WinCE
from what I understood while working at Rockwell... Also an embedded Linux
derivative...

[Jim Logajan]

"Grumman-581" > wrote:
> "Jim Logajan" > wrote in message
> .. .
>> Which ones? (I'd like to know what avionics use MS Windows so I can
>> know which planes not to get into ;-) )
>
> There are some aircraft systems that use an embedded version of XP and
> WinCE from what I understood while working at Rockwell... Also an
> embedded Linux derivative...

Systems employing embedded Linux I don't have a problem with. Even Wind
River now sells a version of Linux in addition to its VxWorks OS.

[Mxsmanic]

Thomas Borchert writes:

> Sources?

Yes.

> Windows isn't Windows, as you try to make it in your generalization -
> which in itslef implies a certain cluelessness with the topic.

Windows isn't Windows?

> Furthermore, these units are certified to certain reliability levels,
> which are well defined.

Certain _low_ reliability levels.

> Your sweepingly broad statements just aren't true.

Unfortunately they are, and they apply to most commodity,
general-purpose operating systems, not just Windows.

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[Greg Copeland[_1_]]

On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote:

> Greg Copeland writes:
>
>> New systems (P25) already do this type of thing. I develop digital radio
>> systems. Police, fire, FBI, CIA, DoD, DoE, various municipal
>> utilities, and various branches of the military are all taking advantage
>> of this technology. In many cases, the old analog systems must co-exist
>> with the newer P25 systems. In some cases, more rural analog systems
>> actually connect with a P25 network via a specialized repeated.
>> Integration is not a problem.
>
> So why wouldn't it extend to aviation?
>

Great question. I don't have an answer. I've been planting a seed to
have the federal marketing types start sniffing around for FAA/political
upstarts...but so far, for my company, it seems to fall on deaf ears.

>> Last I read, an FAA study indicated they need lots and lots of money
>> (sorry, don't remember the amount) to upgrade their infrastructure from
>> analog to digital.
>
> They need not upgrade it all at once.
>

I agree with that. I didn't read the whole report and it was a couple of
years old. I believe the plan was to upgrade over a number of years...I
don't recall the window.

[snip]
>> Advantages of this technology include:
>> o call queuing - meaning, PTT places you in a queue so you can get a word
>> in, even when the controllers are very busy. BTW, this also means no more
>> "walked on" transmissions.
>
> Do other aircraft hear the transmission when you make it, or when the
> controller hears it? Granted, they are only supposed to listen to the
> controller, but in practice they will be listening to other aircraft
> as well.

Sorry. I forgot most people don't know how this stuff works. You are
queued when you activate your PTT but you don't actually get your "beep"
(think NexTel walkie-talkie sound) back until you're granted your call.
Only after you're granted your call do you speak. Otherwise, no one hears
you because your radio doesn't xmit. Thusly, no more "stomped on" radio
calls.

Example:
Pilot 1 Pilot 2
PTT PTT
"beep"
Pilot speaks
Hears pilot 1
Release PTT
"beep"
Pilot Speaks
Hears pilot 2

>
> How do you make this work in parallel with analog systems that cannot
> queue?
>

The repeater initiates the call on your behalf. The repeater is queued
rather than the analog radio. Likewise, the reply goes to the repeater,
which then re-RXs ("repeats") as analog. For this to work, the analog and
digitial systems must have their own frequencies.

>> o call prioritization - All sorts of cool things can be done here -
>> including, most recent exchange receives priority. Also, should IFR
>> traffic receive higher priority over that of VFR? What about commercial
>> traffic? Priority could be adjusted dynamically too. This means
>> planes in distress could be assigned higher priority. So on and so on...
>
> It's best not to jump off the deep end with gadgets. Just because
> something can be done doesn't mean that it should be done.

Agreed. I was just tossing stuff out to show the types of things that can
be done. A more likely scenario is to give priority to controllers. This
allows controllers to pre-empt pilots when the talk group is busy. Which
is, more than likely the prefered solution.

Also, the concept of "emergency" call is also very useful. For example,
it places you at the top of the queue. Combine "emergency" with a GPS
source, plus data services, and now your squawking 7700, your GPS position
is sent with your PTT, and you now have priority with the controller.

>
>> o caller id - imagine your tail number, altimeter, heading, and aircraft
>> type provided to the controller on every PTT.
>
> Where does this leave people with analog equipment?

An anachronism? ;) No worse off than they are today. Until everyone
is converted, such features would simply be a perk to controllers; with
the potential to increase QoS for those that digitally participate.

>
>> o Limited data services
>
> What kind of data services do pilots need? Are they going to be
> surfing the Web?

Oh, most definiately not web browsing. TAFs, METARS, in route weather,
PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc...

[snip]
>> The only con of digitial compared to analog is reception. With analog,
>> you can hear a weak signal. It may sound like absoluete crap, but you
>> can still hear it. With digitial, either you have a strong enough
>> signal to hear it...and it sounds awesome...or you hear absoluetely
>> nothing at all.
>
> If the digital threshold is set where the threshold of intelligibility
> would be in analog, there's no net loss.

Doesn't work that way. Nor, would you want it to. One of the key points
of digitial radio is that everything is crystal clear. This means lots
and lots of filtering takes place to pull out voice from the background.
If it's intelligible, chances are, it will be considered background noise
and filtered out.


Greg

[Bob Noel]

In article >,
"Grumman-581" > wrote:

> There are some aircraft systems that use an embedded version of XP and WinCE
> from what I understood while working at Rockwell...

Which systems? entertainment system? coffee pot? weather display? PFD?

--
Bob Noel
Looking for a sig the
lawyers will hate

[Jim Logajan]

Greg Copeland > wrote:
> On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote:
>> Do other aircraft hear the transmission when you make it, or when the
>> controller hears it? Granted, they are only supposed to listen to
>> the controller, but in practice they will be listening to other
>> aircraft as well.
>
> Sorry. I forgot most people don't know how this stuff works. You are
> queued when you activate your PTT but you don't actually get your
> "beep" (think NexTel walkie-talkie sound) back until you're granted
> your call. Only after you're granted your call do you speak.

Just tell people they would operate it like a telephone: the pilot would
direct her call to a particular listener (e.g. ATC) and ATC gets a signal
(like a phone ringing!) and can let it ring until they have time to answer
the call. But in a pinch, the system could also act like a party line system
and after hitting the emergency transmit button in her aircraft, the pilot's
distress call would automatically cut in over less-urgent calls to not only
ATC, but to any aircraft who have set their receivers to automatically accept
emergency calls.

In essence, digital systems provide multiple virtual private circuits if
needed, but still allow broadcast or "party" line equivalents for situations
where that communication mode is more useful.

[Jose[_1_]]

> Just tell people they would operate it like a telephone: the pilot would
> direct her call to a particular listener (e.g. ATC) and ATC gets a signal
> (like a phone ringing!)

"Your call is important to us. Our operators are busy right now giving
their full attention to other airlines. We will be with you shortly.
Did you know that you can find most of the information you seek on our
website? Please log on to www.getlostspamcan.com. In the mean time, we
hope you enjoy our new rap hold music."

> after hitting the emergency transmit button in her aircraft

Yanno, this reminds me of what was promised in our health care system
about twenty or thirty years ago.

Jose
--
There are more ways to skin a cat than there are cats.
for Email, make the obvious change in the address.

[Emily[_1_]]

Bob Noel wrote:
> In article >,
> "Grumman-581" > wrote:
>
>> There are some aircraft systems that use an embedded version of XP and WinCE
>> from what I understood while working at Rockwell...
>
> Which systems? entertainment system? coffee pot? weather display? PFD?
>
Hey, the coffee pot's important.

Just kidding. Have you ever seen a coffee pot just pulled off an
airliner? Blech.

[Mxsmanic]

Jim Logajan writes:

> Systems employing embedded Linux I don't have a problem with.

I do. Linux has the same problems for safety-of-life applications as
Windows. All general-purpose operating systems have the same
problems.

--
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[Mxsmanic]

Greg Copeland writes:

> The repeater initiates the call on your behalf. The repeater is queued
> rather than the analog radio. Likewise, the reply goes to the repeater,
> which then re-RXs ("repeats") as analog. For this to work, the analog and
> digitial systems must have their own frequencies.

Is there a guarantee that transmissions will occur within a certain
period? Are these systems verified for safety-of-life applications?

> Also, the concept of "emergency" call is also very useful. For example,
> it places you at the top of the queue. Combine "emergency" with a GPS
> source, plus data services, and now your squawking 7700, your GPS position
> is sent with your PTT, and you now have priority with the controller.

Interesting.

This does bring to mind something else, though: If your channels are
so crowded that you need a system to queue messages and give priority
for emergencies, you need more channels. It's much safer to have
multiple channels that don't require queuing than it is to queue on a
single channel.

Also, how do you deal with analog users who have no queuing? They
will still walk over the simultaneous transmissions in digital and
analog.

> An anachronism? ;) No worse off than they are today.

Actually they would be, since practices extended to digital users
would naturally tend to affect analog users, even though they don't
have the same advantages. This would put them at a safety risk.

> Until everyone
> is converted, such features would simply be a perk to controllers; with
> the potential to increase QoS for those that digitally participate.

Quality of service has to translate to increased safety in my book.
As I've said, if fancy queuing systems are required just to manage
traffic on the channel, then there are not enough channels, digital or
otherwise.

> Oh, most definiately not web browsing. TAFs, METARS, in route weather,
> PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc...

As long as someone is still actually flying the plane. A beautiful
digital display of weather 300 nm ahead doesn't help if it distracts
you from the mountainside looming just ahead through the cockpit
window.

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[Mxsmanic]

Jim Logajan writes:

> Just tell people they would operate it like a telephone: the pilot would
> direct her call to a particular listener (e.g. ATC) and ATC gets a signal
> (like a phone ringing!) and can let it ring until they have time to answer
> the call. But in a pinch, the system could also act like a party line system
> and after hitting the emergency transmit button in her aircraft, the pilot's
> distress call would automatically cut in over less-urgent calls to not only
> ATC, but to any aircraft who have set their receivers to automatically accept
> emergency calls.
>
> In essence, digital systems provide multiple virtual private circuits if
> needed, but still allow broadcast or "party" line equivalents for situations
> where that communication mode is more useful.

What about analog users? What if an analog user transmits while a
queued message is being transmitted?

--
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[Mxsmanic]

Jose writes:

> "Your call is important to us. Our operators are busy right now giving
> their full attention to other airlines. We will be with you shortly.
> Did you know that you can find most of the information you seek on our
> website? Please log on to www.getlostspamcan.com. In the mean time, we
> hope you enjoy our new rap hold music."

"If this is an emergency, press one. If this is a normal call, press
two. If this is a reply to a previous call directed to you, press
three.

If the emergency prevents you from maintaining your assigned altitude,
press one. If it prevents you from maintaining your assigned heading,
press two. If explosive decompression has occurred, press three. If
both pilots are unconscious, press four. If the aircraft has exploded
in midair, press five. If you have struck a mountainside or structure
while waiting for the queued reply to your last call, press six. If
none of these apply, please stand by, and a controller will personally
address your emergency as soon as possible. The current queue is ...
seven ... minutes long. Thank you for waiting.

High fashion reigns at Frammis Terminal's Duty Free Mall, with fall
colors now in stock! Reserve your table via pilot radio at the
Fallingsky lounge for fine dining after touchdown!

The current queue is ... six ... minutes long. Thank you for
waiting."

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[Jay Beckman]

"Mxsmanic" > wrote in message
...

<SNIP>

>
> As long as someone is still actually flying the plane. A beautiful
> digital display of weather 300 nm ahead doesn't help if it distracts
> you from the mountainside looming just ahead through the cockpit
> window.
>

If you're flying something that requires you to be concerned (near term)
with Wx that is 300nm ahead...and you are low enough to hit something that
is part of Earth...you've got larger issues to deal with than how you are
communicating.

;O)

Jay B

[Roger[_4_]]

On Sat, 02 Sep 2006 16:58:12 GMT, "Steven P. McNicoll"
> wrote:

>
>"Ron Natalie" > wrote in message
m...
>>
>> No actually, it's just historical. Early av radio used AM, and for that
>> reason we still do.
>>
>
>Didn't all early radio use AM?

Nope. Used Morse code.
You didn't mean quite that early?



>
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Grumman-581[_3_]]

"Bob Noel" wrote in message
...
> Which systems? entertainment system? coffee pot? weather display? PFD?

I'm not sure which ones were on what type of embedded system since I was
only up there for a 6 month contract and didn't really get much experience
in what all the other groups were doing... Basically my own niche, for the
most part, but I was aware of them using various types of embedded O/Ss for
different things... The portion that I was working on was an embedded Linux
platform... Embedded WinCE was used for some other things and embedded XP
was used for other things... Sorry I can't be more specific, but I really
didn't get a chance to see everything that they were doing up there... What
I did get a chance to see was pretty neat though... Enough to reinforce to
me that if you have the money, someone has a way for you to spend it...

[Grumman-581[_3_]]

"Emily" > wrote in message
. ..
> Hey, the coffee pot's important.

I believe that there are some software controls for the coffee pot... On one
of the aircraft that I was reading the docs on, there were software controls
for various operations and measurements of the waste water system... I don't
remember there being a way of initiating a comode flush via software
though...

[Grumman-581[_3_]]

"Mxsmanic" > wrote in message
...
> I do. Linux has the same problems for safety-of-life applications as
> Windows. All general-purpose operating systems have the same
> problems.

The embedded flavors of Linux that you see on aircraft systems are
*extremely* stripped down... Same with the embedded flavors of WinCE and
WinXP...

[Grumman-581[_3_]]

"Mxsmanic" > wrote in message
...
> Nothing that runs a Windows OS is suitable for safety-of-life
> applications. This is no reflection on Windows; it's just that the
> operating system is designed for general information processing use in
> homes, offices, and schools ... not for process control, real-time
> systems, or mission-critical applications.

Sorry, but you're not quite familiar with the embedded versions of the O/Ss,
so you really can't make that sort of statement with any kind of
certainty... The embedded versions are a completely different beast than the
consumer versions... I might not like Windows, but at least I recognize that
there is a difference between the embedded stuff and the consumer stuff...

[Thomas Borchert]

Mxsmanic,

> > Sources?
>
> Yes.
>

That's all you have to offer?

--
Thomas Borchert (EDDH)

[Stefan]

Mxsmanic schrieb:

> I do. Linux has the same problems for safety-of-life applications as
> Windows. All general-purpose operating systems have the same
> problems.

Point is, stripped down and tweaked embedded versions are not "general
purpose" operating systems, but highly specialized ones which are
surprizingly reliable even if they are called Windows.

Stefan
(usually a declared Windows hater)

[[email protected]]

On Wed, 06 Sep 2006 22:50:20 GMT, "Grumman-581"
> wrote:

>"Steven P. McNicoll" > wrote in message
ink.net...
>> Didn't all early radio use AM?
>
>Technically, they were probably digital... Dashes and dots... <grin>
>
> .-.. .. ...- . / ..-. .- ... -
> -.. .. . / -.-- --- ..- -. --.
> .-.. . .- ...- . / .- / -.-. ..- - . / .-- .. -.. --- .--
>
>----
> --. .-. ..- -- -- .- -. ..... ---.. .---- .--.-. --. -- .- .. .-..
>.-.-.- -.-. --- --
>

You're probably right but putting it into writing with dots & dashes
drives me mad!

After learning morse (up to 20 wpm) about 30 years before getting my
PPL it was easy to ident the VOR's. My instructor was very unhappy
that I would not write down the ID in dots & dashes. Claimed the
iexaminor would not like it. He couldn't believe I found it difficult
to understand morse written as you've done above. Just for fun I tried
to decode your characters, took me a 2-3 minutes to make sense of it.
Much easier to understand as a sequence of musincal type tones :-)

[RST Engineering]

YOu don't want to talk about blech until you've had to change the cabin
airflow filter on a 727 in a cold hangar at 3 am with a hangover back in the
days when you could smoke on board the aircraft. Nicotine, for those of you
who haven't ever seen the raw stuff, mixed with all the rest of the crap
that had flowed through the airplane, strongly resembles drippy malted snot.

Jim




"Emily" > wrote in message
. ..

>
> Just kidding. Have you ever seen a coffee pot just pulled off an
> airliner? Blech.

[Dylan Smith]

On 2006-09-06, Mxsmanic > wrote:
> Thomas Borchert writes:
>> Windows isn't Windows, as you try to make it in your generalization -
>> which in itslef implies a certain cluelessness with the topic.
>
> Windows isn't Windows?

'Windows' is mainly a marketing name. There is a world of difference
between the Windows on GA GPS displays (it'll be the NT microkernel
running software designed by the display maker and will NOT contain the
Win32 subsystem nor the usual crufty device drivers) and Windows on a PC
(which does include the Win32 subsystem and a lot of other cruft).

It's the Win32 subsystem and various Windows drivers that people are
complaining about when they complain about the stability/quality of
Windows. Win32 itself is pretty vile - messy, looks like it was designed
by a dozen teams who never communicated with each other. Like car
crashes, most Windows crashes are caused by bad drivers.

A GA GPS display with the NT microkernel won't contain these buggy
drivers nor the hideous pile of cruft that is the Win32 subsystem. The
NT kernel itself is small and fairly elegant (even if the VMM, in my
opinion, leaves a lot to be desired). It's probably within the realm of
practicality to certify the NT kernel to a certain level of reliability.
(Whether it has been done or not I don't know).

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Thomas Borchert]

Dylan,

> Like car
> crashes, most Windows crashes are caused by bad drivers.
>

I like that ;-)

FWIW, for the PC space, most of the bad drivers are made by legions of
third-party hardware manufacturers. The fact that those legions exist
makes Windows and PCs so cheap and pervasive. It also leads to
problems. Which is why the hard- and software quasi-monopoly employed
by Apple does not have these stability problems as much. It also
explains the much lower marker share of Macs...

Oh, another point: The stability of the Windows PC OS has improved
dramatically with the last two or so versions.

But, as you say, all this is completely irrelevant to the "Windows"
used in avionics.


--
Thomas Borchert (EDDH)

[Mxsmanic]

Thomas Borchert writes:

> That's all you have to offer?

If you have source, that's all you need.

--
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[Mxsmanic]

Dylan Smith writes:

> 'Windows' is mainly a marketing name. There is a world of difference
> between the Windows on GA GPS displays (it'll be the NT microkernel
> running software designed by the display maker and will NOT contain the
> Win32 subsystem nor the usual crufty device drivers) and Windows on a PC
> (which does include the Win32 subsystem and a lot of other cruft).

Even the NT kernel has never been validated or certified for any
safety-of-life use that I'm aware of. There's just too much code.

> It's the Win32 subsystem and various Windows drivers that people are
> complaining about when they complain about the stability/quality of
> Windows. Win32 itself is pretty vile - messy, looks like it was designed
> by a dozen teams who never communicated with each other.

It received an infusion of the very poorly written code from Windows
95 when NT 4.0 was written, from what I recall. It made the OS more
friendly, but less stable and secure. But apparently Microsoft felt
that was what the market wanted, and they were probably right, at
least with respect to desktop machines.

> Like car crashes, most Windows crashes are caused by bad drivers.

Virtually all, not just most.

> A GA GPS display with the NT microkernel won't contain these buggy
> drivers nor the hideous pile of cruft that is the Win32 subsystem. The
> NT kernel itself is small and fairly elegant (even if the VMM, in my
> opinion, leaves a lot to be desired). It's probably within the realm of
> practicality to certify the NT kernel to a certain level of reliability.
> (Whether it has been done or not I don't know).

Avionics software is sometimes verified instruction-by-instruction in
its final binary form. I have a hard time believing that anyone would
do that for NT, even for just the kernel. Even a Linux or UNIX kernel
would be hard to verify.

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[Mxsmanic]

Thomas Borchert writes:

> FWIW, for the PC space, most of the bad drivers are made by legions of
> third-party hardware manufacturers. The fact that those legions exist
> makes Windows and PCs so cheap and pervasive. It also leads to
> problems. Which is why the hard- and software quasi-monopoly employed
> by Apple does not have these stability problems as much. It also
> explains the much lower marker share of Macs...

I find that companies that build nice hardware often build terrible
drivers, and vice versa. You end up having to find a compromise: a
vendor that produces reasonable hardware with reasonable drivers. If
stability is a priority, then you must settle for mediocre hardware
with good drivers; if features are a priority, you must settle for
bug-laden, system-crashing drivers with great hardware.

> Oh, another point: The stability of the Windows PC OS has improved
> dramatically with the last two or so versions.

Windows has been stable since NT was first released. NT 4
destabilized things a bit in its attempt to ape the features of
Windows 95.

--
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[Jim Logajan]

Dylan Smith > wrote:
> Like car crashes, most Windows crashes are caused by bad drivers.

The same is true of all operating systems; I once had a Sun Solaris system
crash because the tape driver had a bug.

It's been a while since I worked on any RTOS, but I seem to (probably
incorrectly) recall that applications running on VxWorks (the OS used on
the Mars Explorer, among other spacecraft) generally have full run of the
memory. That is, there is no distinction between the app and the OS as far
as access privileges to memory or I/O.

And I'll admit it eventually doesn't matter how reliable the OS is once it
passes a certain reasonable level, since the application(s) are always
going to be less reliable. If your app crashes, you may not get a "blue
screen" but the end result for the pilot is the same: they have to restart
the app somehow, and a cold restart is generally the easiest. (Though if
the OS is running okay it can tell when the app dies and do a warm restart
on the pilot's behalf.)

[Mxsmanic]

"Grumman-581" > writes:

> The embedded flavors of Linux that you see on aircraft systems are
> *extremely* stripped down... Same with the embedded flavors of WinCE and
> WinXP...

If they are stripped enough to be certifiably safe, they are not
longer Linux or Windows.

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[Mxsmanic]

"Grumman-581" > writes:

> I believe that there are some software controls for the coffee pot... On one
> of the aircraft that I was reading the docs on, there were software controls
> for various operations and measurements of the waste water system...

Sounds like an Airbus.

--
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[Mxsmanic]

"Grumman-581" > writes:

> Sorry, but you're not quite familiar with the embedded versions of the O/Ss,
> so you really can't make that sort of statement with any kind of
> certainty... The embedded versions are a completely different beast than the
> consumer versions...

Then they aren't Windows.

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[Mxsmanic]

Jim Logajan writes:

> It's been a while since I worked on any RTOS, but I seem to (probably
> incorrectly) recall that applications running on VxWorks (the OS used on
> the Mars Explorer, among other spacecraft) generally have full run of the
> memory. That is, there is no distinction between the app and the OS as far
> as access privileges to memory or I/O.

It makes sense, since anything used in a truly mission-critical
environment has to be error-free for the mission to succeed.
Protecting the OS against applications serves no purpose, because any
error in the applications will negatively impact or destroy the
mission, anyway. In other words, even if the OS is protected against
an application bug, the mere fact that there is a bug is going to
prevent the mission from being carried out, so one gains nothing by
protecting the OS.

Ultimately you end up with a system that is entirely OS, with
everything being privileged. A system that enforces restricted user
privileges just does so to protect against poorly-written software;
but you cannot afford poorly-written software to begin with in
mission-critical systems, so such restrictions are too little, too
late, if something goes wrong.

> And I'll admit it eventually doesn't matter how reliable the OS is once it
> passes a certain reasonable level, since the application(s) are always
> going to be less reliable.

And vice versa. If it's all mission-critical, there's no reason to
restrict any of it, because it all has to be 100% trustworthy to begin
with.

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[Grumman-581[_3_]]

"Mxsmanic" > wrote in message
...
> If they are stripped enough to be certifiably safe, they are not
> longer Linux or Windows.

Are you naturally this dense or did you have to work at it? There is no ONE
****in' version of Linux nor even Windows... We're talking a completely
different ****in' world from what you are familiar with... I would suggest
that perhaps you should consider only voicing opinions on things that you
might be competent in discussing, but that would probably prevent you from
being able to post...

[Grumman-581[_3_]]

"Mxsmanic" > wrote in message
...
> Sounds like an Airbus.

Perhaps... Perhaps it was one of the Bombadier aircraft... I was reading so
many docs while coming up to speed on the project that it all kind of
blurred together after awhile... The best I remember, there were temperature
sensors in the waste water system in addition to heaters for the lines so
that the temperature at altitude didn't cause everything to freeze up...
Various sensors could be read and were to be displayed on certain displays
if they exceeded some particular normal operating range, IIRC... There was
this one particular cabin lighting system that consisted of red, green, and
blue LEDs with software control of the intensity and color for various zones
in the aircraft... You would send a particular formated TCP/IP message via a
socket connection to a particular controller that would then change the
intensity of the LEDs in the specified zone... Quite a bit of the
communication between the various devices was handled via TCP/IP
communication... I believe that Rockwell had been granted a patent on that
approach...

[Stefan]

Mxsmanic schrieb:

> If they are stripped enough to be certifiably safe, they are not
> longer Linux or Windows.

Windows is nothing more than a copyrighted name, and Microsoft is free
to sell anything they want under this name. If they decide to call that
stripped, reliable code Windows, then yes, it *is* Windows.

Stefan

[Bob Noel]

In article >,
Jim Logajan > wrote:

> It's been a while since I worked on any RTOS, but I seem to (probably
> incorrectly) recall that applications running on VxWorks (the OS used on
> the Mars Explorer, among other spacecraft) generally have full run of the
> memory. That is, there is no distinction between the app and the OS as far
> as access privileges to memory or I/O.

There are versions of VxWorks that are certifiable to DO-178B level A.
Kind of hard to do that while allowing full run of the memory.

>
> And I'll admit it eventually doesn't matter how reliable the OS is once it
> passes a certain reasonable level, since the application(s) are always
> going to be less reliable.

um, not always. the complexity of the OS could dominate the complexity
of the app, especially if the OS provides protection for the app (e.g.,
partitioning).

--
Bob Noel
Looking for a sig the
lawyers will hate

[Greg Copeland[_1_]]

On Thu, 07 Sep 2006 07:41:03 +0200, Mxsmanic wrote:

> Greg Copeland writes:
>
>> The repeater initiates the call on your behalf. The repeater is queued
>> rather than the analog radio. Likewise, the reply goes to the repeater,
>> which then re-RXs ("repeats") as analog. For this to work, the analog and
>> digitial systems must have their own frequencies.
>
> Is there a guarantee that transmissions will occur within a certain
> period? Are these systems verified for safety-of-life applications?
>

You consider DoD, DoE, CIA, FBI, military, fire, and police to be
"safety-of-life applications?" If so, yes. Do keep in mind, these are
existing systems but do not specifically target aviation. I would imagine
aviation would require some adaptation or P25 or a P25-like standard.

>> Also, the concept of "emergency" call is also very useful. For example,
>> it places you at the top of the queue. Combine "emergency" with a GPS
>> source, plus data services, and now your squawking 7700, your GPS position
>> is sent with your PTT, and you now have priority with the controller.
>
> Interesting.
>
> This does bring to mind something else, though: If your channels are
> so crowded that you need a system to queue messages and give priority
> for emergencies, you need more channels. It's much safer to have
> multiple channels that don't require queuing than it is to queue on a
> single channel.
>

Yes. That's a function of scalability. It's up to the customer (FAA in
this case) to ensure enough talk groups exist to meet their often growing
needs. As it applies to aviation, talk groups would be ground, tower,
departure, arrival, etc...

Also, I don't want to be misleading. Queuing serves as a short term
solution for **peak** periods. In other words, queuing is only honored
for brief periods of time; usually in the 1-3 second range. The notion is
to allow for first-come, first-serve without forcing users to constantly
rekey their PTT if they didn't get their call grant. If a queue depth
greater than one becomes the norm, someone failed to properly scale the
system.

> Also, how do you deal with analog users who have no queuing? They
> will still walk over the simultaneous transmissions in digital and
> analog.

Analog users would require an analog system to sit beside it or you would
require an analog/digital repeater. I must profess, I've never used the
analog P25 repeater. I'm in the P25 infrastructure development group at
my company so I don't use the analog stuff. As such, I must profess some
ignorance.

>
>> An anachronism? ;) No worse off than they are today.
>
> Actually they would be, since practices extended to digital users
> would naturally tend to affect analog users, even though they don't
> have the same advantages. This would put them at a safety risk.

How so? How is a current analog user "at risk"? It's not like it's
removing existing capabilities.

>
>> Until everyone
>> is converted, such features would simply be a perk to controllers; with
>> the potential to increase QoS for those that digitally participate.
>
> Quality of service has to translate to increased safety in my book.
> As I've said, if fancy queuing systems are required just to manage
> traffic on the channel, then there are not enough channels, digital or
> otherwise.

With analog, you don't have a queuing system...which translates directly
into walked on radio calls. That's a loss of service and wasted airtime.
"Fancy" queuing and resource allocation immediately translates into
increased QoS. In this case, that translates to increased safety. That's
just for starters, directly comparing analog to digital. By having an
analog to P25 repeater, on the digital side, you reap the same benefits.

>
>> Oh, most definiately not web browsing. TAFs, METARS, in route weather,
>> PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc...
>
> As long as someone is still actually flying the plane. A beautiful
> digital display of weather 300 nm ahead doesn't help if it distracts
> you from the mountainside looming just ahead through the cockpit
> window.

If you're trying to get weather while flying toward a mountain, you have
priority issues which conflict with safety. Somehow, I don't imagine data
services will be the probable cause of death.

Lastly, let me stress, I'm talking about existing services which does NOT
serve aviation; save only a few police helicopters and planes. And those
radios are used for unit to unit (person to person) and group calls
("party line")...not for aviation specific communication. As I said
above, I'm sure parts of P25 would need to be adapted to better serve the
needs of pilots. Nonetheless, the technology is both here and proven.


Greg

[Greg Copeland[_1_]]

On Thu, 07 Sep 2006 02:11:51 +0000, Jim Logajan wrote:

> Greg Copeland > wrote:
>> On Sun, 03 Sep 2006 15:37:38 +0200, Mxsmanic wrote:
>>> Do other aircraft hear the transmission when you make it, or when the
>>> controller hears it? Granted, they are only supposed to listen to
>>> the controller, but in practice they will be listening to other
>>> aircraft as well.
>>
>> Sorry. I forgot most people don't know how this stuff works. You are
>> queued when you activate your PTT but you don't actually get your
>> "beep" (think NexTel walkie-talkie sound) back until you're granted
>> your call. Only after you're granted your call do you speak.
>
> Just tell people they would operate it like a telephone: the pilot would
> direct her call to a particular listener (e.g. ATC) and ATC gets a signal
> (like a phone ringing!) and can let it ring until they have time to answer
> the call.

That would be very frowned upon. A unit to unit call (like a non-party
line telephone) would tie up resources which should otherwise be shared.
That's not to say they don't have their place, but it's not something you
would want happening all the time.

> But in a pinch, the system could also act like a party line system
> and after hitting the emergency transmit button in her aircraft, the pilot's
> distress call would automatically cut in over less-urgent calls to not only
> ATC, but to any aircraft who have set their receivers to automatically accept
> emergency calls.

Emergency calls can be group calls just as they are today with their
analog equivalent. The point of an emergency call is to give priority to
your conversation with someone on the other end. Anything beyond that is
a perk.

>
> In essence, digital systems provide multiple virtual private circuits if
> needed, but still allow broadcast or "party" line equivalents for situations
> where that communication mode is more useful.

I would emphasize it the other way around. A unit to unit call ties up an
entire channel for its duration. So you would not want that to be the
common case.

Greg

[Greg Copeland[_1_]]

On Thu, 07 Sep 2006 07:41:55 +0200, Mxsmanic wrote:

> Jim Logajan writes:
>
>> Just tell people they would operate it like a telephone: the pilot would
>> direct her call to a particular listener (e.g. ATC) and ATC gets a signal
>> (like a phone ringing!) and can let it ring until they have time to answer
>> the call. But in a pinch, the system could also act like a party line system
>> and after hitting the emergency transmit button in her aircraft, the pilot's
>> distress call would automatically cut in over less-urgent calls to not only
>> ATC, but to any aircraft who have set their receivers to automatically accept
>> emergency calls.
>>
>> In essence, digital systems provide multiple virtual private circuits if
>> needed, but still allow broadcast or "party" line equivalents for situations
>> where that communication mode is more useful.
>
> What about analog users? What if an analog user transmits while a
> queued message is being transmitted?

Normally, the duration between keying and the call grant is very. It's
measured in milliseconds. This means, the analog users PTTs and starts
talking, assuming he doesn't already hear someone talking. The grant
comes back to the repeater and it starts repeating. That means the
digital portion is some number of milliseconds behind the analog portion.
If someone else on the analog side walks on your analog call, I imagine
the DSP will do its best to filter it out. That probably means your call
it terminated before you intended or it's removed. If an analog user
talks over the P25 repeater, repeating from the digital side (xmiting
analog), then you have the classic walked on radio call problem. That is,
after all, one of the problems of analog radio.

And from my first posting on the topic:
>>
>> How do you make this work in parallel with analog systems that cannot
>> queue?
>>
>
>The repeater initiates the call on your behalf. The repeater is queued
>rather than the analog radio. Likewise, the reply goes to the repeater,
>which then re-RXs ("repeats") as analog. For this to work, the analog
>and digitial systems must have their own frequencies.

Hopefully this clears things up.

Greg

[Mxsmanic]

Bob Noel writes:

> There are versions of VxWorks that are certifiable to DO-178B level A.
> Kind of hard to do that while allowing full run of the memory.

Why?

> um, not always. the complexity of the OS could dominate the complexity
> of the app, especially if the OS provides protection for the app (e.g.,
> partitioning).

In mission-critical systems, all of the software works as an
integrated whole; you don't just load arbitrary code off a CD and run
it. If you are running untrustworthy code, you're also running
uncertified/unvalidated code, which is dangerous.

--
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[Mxsmanic]

Stefan writes:

> Windows is nothing more than a copyrighted name, and Microsoft is free
> to sell anything they want under this name. If they decide to call that
> stripped, reliable code Windows, then yes, it *is* Windows.

But then it's not a desktop or server Windows, which is what most
people have in mind when they use the adjective.

Windows is not copyrighted, it's trademarked, as an adjective.

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[Mxsmanic]

"Grumman-581" > writes:

> You would send a particular formated TCP/IP message via a
> socket connection to a particular controller that would then change the
> intensity of the LEDs in the specified zone...

Seriously? Is it an aircraft or a video game?

And people think I'm being extreme in suggesting FM radio instead of
AM radio?

> Quite a bit of the
> communication between the various devices was handled via TCP/IP
> communication... I believe that Rockwell had been granted a patent on that
> approach...

A patent on TCP/IP? Would anyone really want to steal something based
on TCP/IP?

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[Grumman-581[_3_]]

"Mxsmanic" > wrote in message
...
> Seriously? Is it an aircraft or a video game?

Yeah, I'm very serious... In fact, it cuts down on the wiring... Think of
multiple control stations aboard an aircraft being able to control various
pieces of hardware... With the typical analog controls like you have for
lights in your house, you would be running 110VAC all over everywhere...
With this sort of system, you run power to the actual device and use lower
gauge wires for sending signals to the controller for that device... Think
of it as every device that you want to possibly control having a particular
IP address and port number... You format a command and send it to the
device... Perhaps this one controller handles multiple physical devices and
the format of the message indicates which device is to be controlled or
queried with respect to its current status... Would you rather hligh voltage
running all around the aircraft or just where it was really needed and
basically the equivalent of phone (i.e. CAT-5/6) wire running everywhere
else? In addition to this, the controls for the cabin entertainment system
also were TCP/IP based... Even the video and audio that was piped throughout
the cabin went over a TCP/IP connection -- UDP, actually...

> And people think I'm being extreme in suggesting FM radio instead of
> AM radio?

Well, that's because FM doesn't provide any real benefit as compared to AM
for aircraft communications... As I've shown in the above aircraft, using
TCP/IP for communication / control of various devices aboard an aircraft can
definitely provide a certain benefit...

> A patent on TCP/IP? Would anyone really want to steal something based
> on TCP/IP?

No, a patent on the idea of using TCP/IP for communication between various
systems aboard an aircraft... Or maybe it's a copywrite... Whatever...

[Thomas Borchert]

Mxsmanic,

> If they are stripped enough to be certifiably safe, they are not
> longer Linux or Windows.
>

If the manufacturer calls it Windows, it is Windows, period. Man, this
is really simple...

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Mxsmanic,

> Then they aren't Windows.
>

You are wrong. Again.

--
Thomas Borchert (EDDH)

[Dylan Smith]

On 2006-09-08, Grumman-581 <grumman581@DIE-SPAMMER-SCUM> wrote:
> No, a patent on the idea of using TCP/IP for communication between various
> systems aboard an aircraft... Or maybe it's a copywrite... Whatever...

It could be either or both. The code would be copyrighted by default,
and the method itself could be patented. However, just like most patents
issued by the USPTO today, it's barely worthy of a patent because it's
just so obvious to control devices using data passed down some data
connection (such as TCP/IP). I suspect they used TCP/IP rather than
concocting their own control protocol because TCP/IP (for all its warts)
is well understood and TCP/IP stacks are ubiquitous on virtually any
device (including microcontrollers) with even trivial amounts of
processing power - thus reducing development costs.

--
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Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

[Randy Aldous]

[snip]
> to understand morse written as you've done above. Just for fun I tried
> to decode your characters, took me a 2-3 minutes to make sense of it.
> Much easier to understand as a sequence of musincal type tones :-)

I'll admit I cheated a little. Go to
http://www.onlineconversion.com/morse_code.htm and you can paste the
dots and dashes in and get a english translation. Works the other way
too.

Randy

[[email protected]]

Mxsmanic wrote:
> Perhaps this is a naive question, but: Why don't voice radio
> communications for aviation use FM radio instead of AM radio?

FM offers better quality that AM when signal is relatively strong (or
signal to noise ratio is high). As the signal strength decreases, there
is a point when the quality is identical in both cases and then the
quality of FM deteriorates _rapidly_, while AM is still usable.
So, it might be a safety issue - using FM would effectively filter out
the weakest stations that could be heard if AM was used. Just a theory
;-)

Bartek

[Mxsmanic]

"Grumman-581" > writes:

> Yeah, I'm very serious... In fact, it cuts down on the wiring...

Which means that a single break in a single wire disables multiple
aircraft systems. Brilliant.

> Think of
> multiple control stations aboard an aircraft being able to control various
> pieces of hardware... With the typical analog controls like you have for
> lights in your house, you would be running 110VAC all over everywhere...

I could never find a justification for those home remote control
systems that used house wiring, and they weren't always reliable,
anyway.

> Well, that's because FM doesn't provide any real benefit as compared to AM
> for aircraft communications... As I've shown in the above aircraft, using
> TCP/IP for communication / control of various devices aboard an aircraft can
> definitely provide a certain benefit...

It makes things cheaper, I suppose. I'm not sure I see a safety
benefit, and there might even be a reduction in safety.

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