Mythbusters Episode and FMS

[Marco Leon]

Saw a repeat episode of Mythbusters for the first time last night about
the use of cell phones on an airplane and interference with cockpit
instruments. I know that this was mentioned in a November 2006 thread
briefly but the short of it was that they concluded cell phones really
CAN interfere with the VOR signals.

One of the tests however, was on a Hawker jet with a glass cockpit
(Honeywell I believe) with a FMS. They could not get any frequencies or
amplitude of cellphone signals to budge the instruments like they were
able to on a 1970's era NAV system. From what I understand, the FMS
relies on a number of different inputs to drive its nav systems. If
that's the case, wouldn't it switch to another source if one seemed
unreliable? If it does, I imagine it would be a fundamental flaw in
their experiment. The FBO manager and avionics guy being interviewed
however, gave the nod to the robust wire shielding.

Marco

[Bill Denton]

Keep in mind that there is a difference between "valid" and "correct".

For example, a computer program may require that a number be entered in a
specific field.

Any number that is entered would be "valid", but it would not necessarily be
"correct".

A given electronic device might cause a reading to be 10 degrees off. The
nav system might well interpret the data as "valid" even though it would not
be correct.





"Marco Leon" > wrote in message
oups.com...
> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.
>
> One of the tests however, was on a Hawker jet with a glass cockpit
> (Honeywell I believe) with a FMS. They could not get any frequencies or
> amplitude of cellphone signals to budge the instruments like they were
> able to on a 1970's era NAV system. From what I understand, the FMS
> relies on a number of different inputs to drive its nav systems. If
> that's the case, wouldn't it switch to another source if one seemed
> unreliable? If it does, I imagine it would be a fundamental flaw in
> their experiment. The FBO manager and avionics guy being interviewed
> however, gave the nod to the robust wire shielding.
>
> Marco
>

[Marco Leon]

On Jan 25, 11:47 am, "Bill Denton" > wrote:
> Keep in mind that there is a difference between "valid" and "correct".
>
> For example, a computer program may require that a number be entered in a
> specific field.
>
> Any number that is entered would be "valid", but it would not necessarily be
> "correct".
>
> A given electronic device might cause a reading to be 10 degrees off. The
> nav system might well interpret the data as "valid" even though it would not
> be correct.

Agreed. However, having a choice of signals to "believe," the FMS
should have an integrity check in its logic, right? If the VOR-NAV is
showing you 3 miles to the left of the localizer and the GPS and INS
are showing you on it, then the FMS should disregard the VOR-NAV.

Also, there may be other ways of verifying integrity such as the
presence of wild fluctuations in a given period of time.

Marco

[Mxsmanic]

Marco Leon writes:

> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.

At very close range and in certain positions, yes. But that doesn't
mean that using a cell phone in a seat in the middle of the aircraft
will do anything. There's already a lot of RF noise in the air around
aircraft.

> One of the tests however, was on a Hawker jet with a glass cockpit
> (Honeywell I believe) with a FMS. They could not get any frequencies or
> amplitude of cellphone signals to budge the instruments like they were
> able to on a 1970's era NAV system. From what I understand, the FMS
> relies on a number of different inputs to drive its nav systems. If
> that's the case, wouldn't it switch to another source if one seemed
> unreliable?

Yes, within limits.

> If it does, I imagine it would be a fundamental flaw in
> their experiment. The FBO manager and avionics guy being interviewed
> however, gave the nod to the robust wire shielding.

I suspect the shielding is actually protecting the avionics. They
have to be shielded just to prevent interference with each other, much
less interference from cell phones.

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

[Mxsmanic]

Marco Leon writes:

> Agreed. However, having a choice of signals to "believe," the FMS
> should have an integrity check in its logic, right? If the VOR-NAV is
> showing you 3 miles to the left of the localizer and the GPS and INS
> are showing you on it, then the FMS should disregard the VOR-NAV.

Yes, it should have such checks, and it does.

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

[Grumman-581[_1_]]

On Thu, 25 Jan 2007 08:15:54 -0800, in
. com>, Marco Leon wrote:

<snip>

Although they are not that bad of a show to watch sometimes, I've noticed
some of their experiments that were not exactly right... They did one on
exiting a car underwater recently... Their experiments methods came to the
conclusion that it was not possible to roll the window down on a car once
it was submerged due to the pressure on the window... To simulate this,
they put some weights on the window of a car door held in a horizontal
position... If you look closely at it, it seems pretty obvious that the
weights window was cracking open up to the point where the weights started
hitting the bottom edge of the window... I suspect that the results
from water pressure being distributed across the face of the window
would not act the same... At the very least, even the small amount that
the window would open would allow the water to enter the vehicle quicker
and as such equalize pressure quicker and thus allow you to open the door
quicker...

With regards to the cell phone usage aboard an aircraft, they also said
that they were prevented from doing it in the air because FAA rules made
it illegal... In fact, it is FCC rules and it is because of concerns of
the phones contacting multiple cell phone towers at the same time... The
way I understand it, the FAA rules concern airliners, so with regards to
that, they could have made the test on a VFR flight without any FAA
consequences...

Now, this doesn't address the issue of whether you can even get a cell
phone signal while in the air... My experience with Verizon is that above
about 500 ft or so, if a signal is available, it doesn't last long enough
for me to make a call... On the other hand, the old analog cell phones
would work at 10K ft... Of course, this was back in the old bag phone days
with a real handset, so you had to cut the engine back to idle slow down
as much as possible to reduce the engine and wind noise so that you could
actually hear what was said on the phone... Let's just say that it was not
conducive towards long conversations...

[Robert M. Gary]

No, all their tests were done with localizers, no VORs at all. Probably
no back up of that.
However, the show failed to mention that its the FCC rule that states,
no cell phones on in planes ever. The FAA rules are less strict.

-Robert


On Jan 25, 8:15 am, "Marco Leon" > wrote:
> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.
>
> One of the tests however, was on a Hawker jet with a glass cockpit
> (Honeywell I believe) with a FMS. They could not get any frequencies or
> amplitude of cellphone signals to budge the instruments like they were
> able to on a 1970's era NAV system. From what I understand, the FMS
> relies on a number of different inputs to drive its nav systems. If
> that's the case, wouldn't it switch to another source if one seemed
> unreliable? If it does, I imagine it would be a fundamental flaw in
> their experiment. The FBO manager and avionics guy being interviewed
> however, gave the nod to the robust wire shielding.
>
> Marco

[Darkwing]

"Grumman-581" > wrote in message
...
> On Thu, 25 Jan 2007 08:15:54 -0800, in
> . com>, Marco Leon wrote:
>
> <snip>
>
> Although they are not that bad of a show to watch sometimes, I've noticed
> some of their experiments that were not exactly right... They did one on
> exiting a car underwater recently... Their experiments methods came to the
> conclusion that it was not possible to roll the window down on a car once
> it was submerged due to the pressure on the window... To simulate this,
> they put some weights on the window of a car door held in a horizontal
> position... If you look closely at it, it seems pretty obvious that the
> weights window was cracking open up to the point where the weights started
> hitting the bottom edge of the window... I suspect that the results
> from water pressure being distributed across the face of the window
> would not act the same... At the very least, even the small amount that
> the window would open would allow the water to enter the vehicle quicker
> and as such equalize pressure quicker and thus allow you to open the door
> quicker...


I seen the exact same thing last night. Why they just didn't submerge the
car and let Jamie mess with it with his scuba gear on was a little dumb, it
would have taken 2 minutes.

-----------------------------------
DW

[Grumman-581[_1_]]

On Thu, 25 Jan 2007 13:06:37 -0800, in
. com>, Robert M. Gary
wrote:
> However, the show failed to mention that its the FCC rule that states,
> no cell phones on in planes ever. The FAA rules are less strict.

Correct... And since they're in CA, they could have flown far enough
offshore to be out of the jurisdiction of the FCC... They would also have
been far enough out that the cell phone signal would not have interfered
with any of the cell phone towers (assuming that is even still an issue
with the digital phones of today)...

[C J Campbell]

On Thu, 25 Jan 2007 08:15:54 -0800, Marco Leon wrote
(in article . com>):

> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.


Yeah, sure. In addition to the other objections mentioned, it would be
interesting to know if they used a real cell phone and if they did, where
they got it and if it was damaged in any way. Digital PCS phones, which are
much more common nowadays, are also much less likely to interfere with
avionics.

Mythbusters has been going out on a limb and sawing it off lately.
Mythbusters BUSTED!

--
Waddling Eagle
World Famous Flight Instructor

[Robert M. Gary]

On Jan 25, 1:59 pm, Grumman-581
> wrote:
> On Thu, 25 Jan 2007 13:06:37 -0800, in
> . com>, Robert M. Gary
> wrote:
>
> > However, the show failed to mention that its the FCC rule that states,
> > no cell phones on in planes ever. The FAA rules are less strict.Correct... And since they're in CA, they could have flown far enough
> offshore to be out of the jurisdiction of the FCC... They would also have
> been far enough out that the cell phone signal would not have interfered
> with any of the cell phone towers (assuming that is even still an issue
> with the digital phones of today)...

It would have been more interesting if they talked about the FCC's
reasons for their ban and if current technology could still cause
problems with towers.

-Robert

[Kyle Boatright]

"Marco Leon" > wrote in message
oups.com...
> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.
>
>
> Marco

And they are probably right. Not the same hardware, obviously, but I have
seen my portable MP3 player interfere with my portable GPS. Until someone
"certifies" a particular brand/model of electronic item for in-flight use,
there isn't any guarantee that the device won't cause some sort of glitch in
the sensitive nav equipment on an airplane. I know the chance is remote,
but I'd rather not take it...

KB

[[email protected]]

On Jan 25, 8:15 am, "Marco Leon" > wrote:
> Saw a repeat episode of Mythbusters for the first time last night about
> the use of cell phones on an airplane and interference with cockpit
> instruments. I know that this was mentioned in a November 2006 thread
> briefly but the short of it was that they concluded cell phones really
> CAN interfere with the VOR signals.

Sometime in the last year or two, the IEEE (the main EE professional
society) had an authoritative article about this in their monthly
magazine "IEEE Spectrum." The bottom line as I remember it: 99.999% of
cell phones and other electronic gizmos cause absolutely no
interference to flight instruments. (The 99.999% figure is indicative,
not exact.) But, very rarely a cell phone or other electronic device
gets out of spec on RFI (but still "works" so far as the user is
concerned) and can make the FI's go haywire.

The authors conclude that unrestricted use of cell phones and other
electronic devices (including ones now allowed) will probably cause a
crash something like once every decade or so. I forget the number, but
it's in that ball park -- the kind of thing that, until it happens, the
regs seem overly restrictive. But after it happens, everyone will ask
"Why didn't they ban those devices?" If memory serves me, the authors
cannot rule out that such crashes have already happened.

The authors had done a study in which they planted a measuring device
in a suitcase and flew it on a large number of flights in an overhead
bin, and recorded the EM spectrum. Interestingly, they found cell
phones were used illegally about once per flight or thereabouts. They
also found a number of cases where a device had failed, at least in the
sense that its spectrum could cause interference to GPS and other FI's.
They also reported one incident where an airliner's FI's went haywire
and the captain asked everyone to shut down all electronic devices. The
FI's recovered, and a bit of sleuthing traced the problem to one
passenger's device.

[**THE-RFI-EMI-GUY**]

Its just plain good sense not to use cellphones in an aircraft. Has
anyone noticed how a NEXTEL phone will tear up speaker phones and
computer monitors? Its the pulsing of the time division multiplex (TDMA)
RF signal that gets inadvertently coupled into electronics and biases
transistors on and off. Think what would happen if a passenger left that
phone turned on in a bag near a bulkhead next to some sensitive avionics
box and a call came in. Whenever I read about A/C having "uncommanded"
control movement, I have to wonder about that environment.

wrote:

>On Jan 25, 8:15 am, "Marco Leon" > wrote:
>
>
>>Saw a repeat episode of Mythbusters for the first time last night about
>>the use of cell phones on an airplane and interference with cockpit
>>instruments. I know that this was mentioned in a November 2006 thread
>>briefly but the short of it was that they concluded cell phones really
>>CAN interfere with the VOR signals.
>>
>>
>
>Sometime in the last year or two, the IEEE (the main EE professional
>society) had an authoritative article about this in their monthly
>magazine "IEEE Spectrum." The bottom line as I remember it: 99.999% of
>cell phones and other electronic gizmos cause absolutely no
>interference to flight instruments. (The 99.999% figure is indicative,
>not exact.) But, very rarely a cell phone or other electronic device
>gets out of spec on RFI (but still "works" so far as the user is
>concerned) and can make the FI's go haywire.
>
>The authors conclude that unrestricted use of cell phones and other
>electronic devices (including ones now allowed) will probably cause a
>crash something like once every decade or so. I forget the number, but
>it's in that ball park -- the kind of thing that, until it happens, the
>regs seem overly restrictive. But after it happens, everyone will ask
>"Why didn't they ban those devices?" If memory serves me, the authors
>cannot rule out that such crashes have already happened.
>
>The authors had done a study in which they planted a measuring device
>in a suitcase and flew it on a large number of flights in an overhead
>bin, and recorded the EM spectrum. Interestingly, they found cell
>phones were used illegally about once per flight or thereabouts. They
>also found a number of cases where a device had failed, at least in the
>sense that its spectrum could cause interference to GPS and other FI's.
>They also reported one incident where an airliner's FI's went haywire
>and the captain asked everyone to shut down all electronic devices. The
>FI's recovered, and a bit of sleuthing traced the problem to one
>passenger's device.
>
>
>

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

[[email protected]]

On Feb 10, 10:19 pm, **THE-RFI-EMI-GUY** >
wrote:
> Its just plain good sense not to use cellphones in an aircraft. Has
> anyone noticed how a NEXTEL phone will tear up speaker phones and
> computer monitors? Its the pulsing of the time division multiplex (TDMA)
> RF signal that gets inadvertently coupled into electronics and biases
> transistors on and off. Think what would happen if a passenger left that
> phone turned on in a bag near a bulkhead next to some sensitive avionics
> box and a call came in. Whenever I read about A/C having "uncommanded"
> control movement, I have to wonder about that environment.
>
>
>
>
>
> wrote:
> >On Jan 25, 8:15 am, "Marco Leon" > wrote:
>
> >>Saw a repeat episode of Mythbusters for the first time last night about
> >>the use of cell phones on an airplane and interference with cockpit
> >>instruments. I know that this was mentioned in a November 2006 thread
> >>briefly but the short of it was that they concluded cell phones really
> >>CAN interfere with the VOR signals.
>
> >Sometime in the last year or two, the IEEE (the main EE professional
> >society) had an authoritative article about this in their monthly
> >magazine "IEEE Spectrum." The bottom line as I remember it: 99.999% of
> >cell phones and other electronic gizmos cause absolutely no
> >interference to flight instruments. (The 99.999% figure is indicative,
> >not exact.) But, very rarely a cell phone or other electronic device
> >gets out of spec on RFI (but still "works" so far as the user is
> >concerned) and can make the FI's go haywire.
>
> >The authors conclude that unrestricted use of cell phones and other
> >electronic devices (including ones now allowed) will probably cause a
> >crash something like once every decade or so. I forget the number, but
> >it's in that ball park -- the kind of thing that, until it happens, the
> >regs seem overly restrictive. But after it happens, everyone will ask
> >"Why didn't they ban those devices?" If memory serves me, the authors
> >cannot rule out that such crashes have already happened.
>
> >The authors had done a study in which they planted a measuring device
> >in a suitcase and flew it on a large number of flights in an overhead
> >bin, and recorded the EM spectrum. Interestingly, they found cell
> >phones were used illegally about once per flight or thereabouts. They
> >also found a number of cases where a device had failed, at least in the
> >sense that its spectrum could cause interference to GPS and other FI's.
> >They also reported one incident where an airliner's FI's went haywire
> >and the captain asked everyone to shut down all electronic devices. The
> >FI's recovered, and a bit of sleuthing traced the problem to one
> >passenger's device.
>
> --
> Joe Leikhim K4SAT
> "The RFI-EMI-GUY"©
>
> "Treason doth never prosper: what's the reason?
> For if it prosper, none dare call it treason."
>
> "Follow The Money" ;-P- Hide quoted text -
>
> - Show quoted text -

Not gonna happen. Avionics have to survive HIRF RF at 100V/M over the
entire RF spectrum.

The real threat is to radio receivers for navigations and
communications. A cell phone can swamp out the receiver and block
important signals. They cannot cause any permanent damage such as you
are describing because of the shielding and other design practices
that are put into place to handle HIRF...

Dean Wilkinson
B.S.E.E. and avionics designer

[Roger[_4_]]

On Sun, 11 Feb 2007 00:19:32 -0500, **THE-RFI-EMI-GUY**
> wrote:

>Its just plain good sense not to use cellphones in an aircraft. Has
>anyone noticed how a NEXTEL phone will tear up speaker phones and
>computer monitors? Its the pulsing of the time division multiplex (TDMA)

Nope. I have both right here and with no problem.

>RF signal that gets inadvertently coupled into electronics and biases
>transistors on and off. Think what would happen if a passenger left that
>phone turned on in a bag near a bulkhead next to some sensitive avionics

The wiring in an aircrafti s well shielded.

>box and a call came in. Whenever I read about A/C having "uncommanded"
>control movement, I have to wonder about that environment.
>
wrote:
>
>>On Jan 25, 8:15 am, "Marco Leon" > wrote:
>>
>>
>>>Saw a repeat episode of Mythbusters for the first time last night about
>>>the use of cell phones on an airplane and interference with cockpit
>>>instruments. I know that this was mentioned in a November 2006 thread
>>>briefly but the short of it was that they concluded cell phones really
>>>CAN interfere with the VOR signals.

Not really. They determined it can be done when none of the wiring in
the test cockpit is shielded.

>>>
>>>
>>
>>Sometime in the last year or two, the IEEE (the main EE professional
>>society) had an authoritative article about this in their monthly
>>magazine "IEEE Spectrum." The bottom line as I remember it: 99.999% of
>>cell phones and other electronic gizmos cause absolutely no
>>interference to flight instruments. (The 99.999% figure is indicative,
>>not exact.) But, very rarely a cell phone or other electronic device
>>gets out of spec on RFI (but still "works" so far as the user is
>>concerned) and can make the FI's go haywire.

A lap top or probably more likely to cause a problem.

>>
>>The authors conclude that unrestricted use of cell phones and other
>>electronic devices (including ones now allowed) will probably cause a
>>crash something like once every decade or so. I forget the number, but

That was one of those programs where the result was it might , maybe,
we think could possibly... IOW they thought the possibility might
exist but could not say any thing specific. Some day one may get hit
by a meteor too. Who knows?

>>it's in that ball park -- the kind of thing that, until it happens, the
>>regs seem overly restrictive. But after it happens, everyone will ask

What regs? Last I knew the FAA had *no* regulations on the use of
cell phones or other electronic radiators in aircraft with one
exception. No intentional radiating devices may be used while the
aircraft is operating by reference to instruments alone and I do not
know if that pertains to commercial flights as well as GA..

The cell phone ban is an FCC regulation which may disappear in the not
too distant future.
Remember as long as it's turned on it's transmitting whether you are
using it or not. Only when turned completely off does it stop
transmitting.
>>"Why didn't they ban those devices?" If memory serves me, the authors
>>cannot rule out that such crashes have already happened.
>>
>>The authors had done a study in which they planted a measuring device
>>in a suitcase and flew it on a large number of flights in an overhead
>>bin, and recorded the EM spectrum. Interestingly, they found cell
>>phones were used illegally about once per flight or thereabouts. They

I find it difficult to believe as every one that was forgotten would
have been transmitting. Many will stop working. I don't know how many
times I've forgotten mine in the Deb but I always have to turn it off
and back on before being able to use it.

>>also found a number of cases where a device had failed, at least in the
>>sense that its spectrum could cause interference to GPS and other FI's.
>>They also reported one incident where an airliner's FI's went haywire
>>and the captain asked everyone to shut down all electronic devices. The
>>FI's recovered, and a bit of sleuthing traced the problem to one
>>passenger's device.
Probably a lap top.
Lap tops and games are particularly bad. Add to that most lap tops now
have built in WiFi.

Generally they aren't a problem and when they have been its been quite
evident.

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

[Dylan Smith]

On 2007-02-12, Roger > wrote:
>>Its just plain good sense not to use cellphones in an aircraft. Has
>>anyone noticed how a NEXTEL phone will tear up speaker phones and
>>computer monitors? Its the pulsing of the time division multiplex (TDMA)
>
> Nope. I have both right here and with no problem.

GSM phones are particularly bad about intefering with things. If I leave
mine by the gearstick of my car (just below the radio), I can hear
every time it hands off between cell towers on the car's radio. I can
also recognise the inteference it makes as a call comes in - so I know
before it rings with a call or beeps with a text message that it's going
to do so because the sound of the inteference is so distinct. It will
intefere with cheap CRT monitors (but not well made more expensive
ones).

I also have a first hand experience of a GSM phone ringing just as we
were intercepting the localiser on a dark, rainy night with 600 foot
ceilings. I was with a friend (who happened to be doing his first for
real ILS). He had forgotten to switch his phone off, and his wife called
just as we were intercepting the localiser. The calm voice of the
tower controller (and everything else) was drowned out by a noise that
went "BIP B B BIP B B BIP B B BIP B B BIP BRRRRRRRRRRRRRRRRRRR". Anyone
with a GSM phone probably recognises that noise if they've ever left
their phone near a radio! Needless to say, it completely obliterated any
radio communications from the tower, and I had to take over flying the
approach while my friend dug into his most inaccessable pocket to find
the offending phone and turn it off.

So far as I can tell it didn't affect the loc or glideslope indications
at all, but it certainly made the com radios completely unusable.

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

[Mike Young]

"Roger" > wrote in message
...
> On Sun, 11 Feb 2007 00:19:32 -0500, **THE-RFI-EMI-GUY**
> > wrote:
>
>>Its just plain good sense not to use cellphones in an aircraft. Has
>>anyone noticed how a NEXTEL phone will tear up speaker phones and
>>computer monitors? Its the pulsing of the time division multiplex (TDMA)
>
> Nope. I have both right here and with no problem.

My old phone, or old service had problems. It would periodically talk to the
cell tower, doing whatever it is that cellphones do. The RF couples strongly
into my audio systems. It was most noticeable in the office when I set the
phone down next to the PC's speaker wire. The amplified speaker made it very
audible; it's louder than normal audio coming from the PC. (I'm qualified to
speak to RFI and EMI in a way you might accept; I hold a fast code Extra
ticket in the US. Eleventh month; region number for great lakes; replaced by
CAT scans; country where you'll find Calcutta.)

[**THE-RFI-EMI-GUY**]

wrote:

>On Feb 10, 10:19 pm, **THE-RFI-EMI-GUY** >
>wrote:
>
>
>>Its just plain good sense not to use cellphones in an aircraft. Has
>>anyone noticed how a NEXTEL phone will tear up speaker phones and
>>computer monitors? Its the pulsing of the time division multiplex (TDMA)
>>RF signal that gets inadvertently coupled into electronics and biases
>>transistors on and off. Think what would happen if a passenger left that
>>phone turned on in a bag near a bulkhead next to some sensitive avionics
>>box and a call came in. Whenever I read about A/C having "uncommanded"
>>control movement, I have to wonder about that environment.
>>
>>
>>
>>
>>
>>snip
>>
>>--
>>Joe Leikhim K4SAT
>>"The RFI-EMI-GUY"©
>>
>>"Treason doth never prosper: what's the reason?
>>For if it prosper, none dare call it treason."
>>
>>"Follow The Money" ;-P- Hide quoted text -
>>
>>- Show quoted text -
>>
>>
>
>Not gonna happen. Avionics have to survive HIRF RF at 100V/M over the
>entire RF spectrum.
>
>The real threat is to radio receivers for navigations and
>communications. A cell phone can swamp out the receiver and block
>important signals. They cannot cause any permanent damage such as you
>are describing because of the shielding and other design practices
>that are put into place to handle HIRF...
>
>Dean Wilkinson
> B.S.E.E. and avionics designer
>
>
>
Do the levels of the HIRF specs pertain to permanent damage or do they
pertain to "upsets"? I wasn't talking about permanent effects. What I
have seen is that these phones very easily cause upsets to consumer
grade equipment. Granted one would expect avionics to be well sheilded.
I would hope that extends to sensors as well.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

[[email protected]]

On Feb 12, 8:51 pm, **THE-RFI-EMI-GUY** > wrote:
> wrote:
> >On Feb 10, 10:19 pm, **THE-RFI-EMI-GUY** >
> >wrote:
>
> >>Its just plain good sense not to use cellphones in an aircraft. Has
> >>anyone noticed how a NEXTEL phone will tear up speaker phones and
> >>computer monitors? Its the pulsing of the time division multiplex (TDMA)
> >>RF signal that gets inadvertently coupled into electronics and biases
> >>transistors on and off. Think what would happen if a passenger left that
> >>phone turned on in a bag near a bulkhead next to some sensitive avionics
> >>box and a call came in. Whenever I read about A/C having "uncommanded"
> >>control movement, I have to wonder about that environment.
>
> >>snip
>
> >>--
> >>Joe Leikhim K4SAT
> >>"The RFI-EMI-GUY"©
>
> >>"Treason doth never prosper: what's the reason?
> >>For if it prosper, none dare call it treason."
>
> >>"Follow The Money" ;-P- Hide quoted text -
>
> >>- Show quoted text -
>
> >Not gonna happen. Avionics have to survive HIRF RF at 100V/M over the
> >entire RF spectrum.
>
> >The real threat is to radio receivers for navigations and
> >communications. A cell phone can swamp out the receiver and block
> >important signals. They cannot cause any permanent damage such as you
> >are describing because of the shielding and other design practices
> >that are put into place to handle HIRF...
>
> >Dean Wilkinson
> > B.S.E.E. and avionics designer
>
> Do the levels of the HIRF specs pertain to permanent damage or do they
> pertain to "upsets"? I wasn't talking about permanent effects. What I
> have seen is that these phones very easily cause upsets to consumer
> grade equipment. Granted one would expect avionics to be well sheilded.
> I would hope that extends to sensors as well.
>
> --
> Joe Leikhim K4SAT
> "The RFI-EMI-GUY"©
>
> "Treason doth never prosper: what's the reason?
> For if it prosper, none dare call it treason."
>
> "Follow The Money" ;-P- Hide quoted text -
>
> - Show quoted text -


Avionics aren't supposed to be upset or damaged by HIRF. For some
categories, test levels can be as high as 200V/M

Consumer grade equipment isn't designed to these standards because
they don't need to be, and they can't be due to cost constraints.
Avionics designs are low volume high cost products...

I have designed for both Laser Printers and avionics, and they have
very different design requirements.

Dean