Metric Instruments [Archive]

Bill Daniels

August 24th 05, 06:25 PM

Does it strike some of the digerati here that expensive mechanical
altimeters with easily mis-read clock-like hands locked into either the
metric or US measurement systems are archaic?

GPS provides highly accurate, although not ATC compliant, altitude. Various
vendors provide electronic pressure altimeters with digital displays that
can be switched between meters and feet with the push of a button. Digital
pressure altitude sensors drive the "glass cockpits" of new GA aircraft.

I seems to me that clock-like altimeters designed 70 years ago and
maintained by watchmakers must be nearing their well-deserved retirement.

Bill Daniels

"Bert Willing" > wrote in
message ...
> Yes, they are.
>
> --
> Bert Willing
>
> ASW20 "TW"
>
>
> "Roy Bourgeois" > a écrit dans le message
de
> news: ...
> > This may be a silly question - but are all metric altimeters
> > configured with 'Zero at 6 O'clock' as I saw in France?
> > I did not have trouble converting to meters/kilometers
> > but I did have trouble quickly reading the altimeter
> > with the zero at the bottom of the instrument face
> > (especially on the little 57mm instruments). Just
> > curious.
> >
> > Roy
> >
> >
> >
> >
>
>

Stefan

August 24th 05, 07:07 PM

Bill Daniels wrote:

> Does it strike some of the digerati here that expensive mechanical
> altimeters with easily mis-read clock-like hands locked into either the
> metric or US measurement systems are archaic?

No, it doesn't. Most probably because the are not archaic, but still
much superior to digital displays, ergonomic wise. Besides, I really
appreciated their purely mechanic design when my battery died in flight.

Stefan

Malcolm Austin

August 24th 05, 08:47 PM

I believe there was some research some years ago, on a similar vein.

The fact seemed to be we "read" clocks almost without thinking. Just the
position of the hands "tells us" what the time is (think of 15 mins to 3
o'clock)

Maybe the altimeter view works the same, which would also make it more
difficult
to adjust to, when it isn't mounted to fit our usual expectations.

(also makes me question the way electrical switches are down for off and up
for
on, in opposition to domestic reality, then we go to hand throttle's!)

Malcolm...

"Bill Daniels" > wrote in message
...
> Does it strike some of the digerati here that expensive mechanical
> altimeters with easily mis-read clock-like hands locked into either the
> metric or US measurement systems are archaic?
>
> GPS provides highly accurate, although not ATC compliant, altitude.
> Various
> vendors provide electronic pressure altimeters with digital displays that
> can be switched between meters and feet with the push of a button.
> Digital
> pressure altitude sensors drive the "glass cockpits" of new GA aircraft.
>
> I seems to me that clock-like altimeters designed 70 years ago and
> maintained by watchmakers must be nearing their well-deserved retirement.
>
> Bill Daniels
>
>
> "Bert Willing" > wrote in
> message ...
>> Yes, they are.
>>
>> --
>> Bert Willing
>>
>> ASW20 "TW"
>>
>>
>> "Roy Bourgeois" > a écrit dans le message
> de
>> news: ...
>> > This may be a silly question - but are all metric altimeters
>> > configured with 'Zero at 6 O'clock' as I saw in France?
>> > I did not have trouble converting to meters/kilometers
>> > but I did have trouble quickly reading the altimeter
>> > with the zero at the bottom of the instrument face
>> > (especially on the little 57mm instruments). Just
>> > curious.
>> >
>> > Roy
>> >
>> >
>> >
>> >
>>
>>
>

Andreas Maurer

August 24th 05, 08:52 PM

On Wed, 24 Aug 2005 11:25:51 -0600, "Bill Daniels"
> wrote:

>Does it strike some of the digerati here that expensive mechanical
>altimeters with easily mis-read clock-like hands locked into either the
>metric or US measurement systems are archaic?
>
>GPS provides highly accurate, although not ATC compliant, altitude. Various
>vendors provide electronic pressure altimeters with digital displays that
>can be switched between meters and feet with the push of a button. Digital
>pressure altitude sensors drive the "glass cockpits" of new GA aircraft.
>
>I seems to me that clock-like altimeters designed 70 years ago and
>maintained by watchmakers must be nearing their well-deserved retirement.

How many times have you praised yourself for having instruments on
board that do not need electricity to work properly? :)

I did that dozens of times - electricity is definitely not a reliable
thing in gliders.

Bye
Andreas

01-- Zero One

August 24th 05, 09:32 PM

Whatever technology is behind the panel (analog or digital), the human
interface for instruments where trends and relative magnitude are
important then the "analog style" gauge is far superior to a digital
readout. It is easily discerned for ballpark, trends up or down, and
actual value rather precisely. So for airspeed indicators, varios, and
the like, the "analog style" interface is the way to go.

For battery voltage levels, radio frequencies, etc. where precision is
more important than trends or "ballpark" then a digital readout is just
the ticket.

Regards,

Larry

"Bill Daniels" > wrote in message
:

> Does it strike some of the digerati here that expensive mechanical
> altimeters with easily mis-read clock-like hands locked into either the
> metric or US measurement systems are archaic?
>
> GPS provides highly accurate, although not ATC compliant, altitude. Various
> vendors provide electronic pressure altimeters with digital displays that
> can be switched between meters and feet with the push of a button. Digital
> pressure altitude sensors drive the "glass cockpits" of new GA aircraft.
>
> I seems to me that clock-like altimeters designed 70 years ago and
> maintained by watchmakers must be nearing their well-deserved retirement.
>
> Bill Daniels
>
>
> "Bert Willing" > wrote in
> message ...
> > Yes, they are.
> >
> > --
> > Bert Willing
> >
> > ASW20 "TW"
> >
> >
> > "Roy Bourgeois" > a écrit dans le message
> de
> > news: ...
> > > This may be a silly question - but are all metric altimeters
> > > configured with 'Zero at 6 O'clock' as I saw in France?
> > > I did not have trouble converting to meters/kilometers
> > > but I did have trouble quickly reading the altimeter
> > > with the zero at the bottom of the instrument face
> > > (especially on the little 57mm instruments). Just
> > > curious.
> > >
> > > Roy
> > >
> > >
> > >
> > >
> >
> >

Bill Daniels

August 24th 05, 10:17 PM

"Andreas Maurer" > wrote in message
...

> How many times have you praised yourself for having instruments on
> board that do not need electricity to work properly? :)
>
> I did that dozens of times - electricity is definitely not a reliable
> thing in gliders.
>
>
>
> Bye
> Andreas

This amazes me. Electricity not reliable? I know this is "conventional
wisdom" but, I have never had an electronic device fail in flight but many,
many mechanical instruments have failed me. In fact, even when an
electronic device seemed to fail, it was always a mechanical switch or
battery contact that failed and not the device itself. (Hint: Use the best
electrical hardware money can buy.)

I sit here typing on an incredibly complex device called a Personal
Computer. The CPU alone has over 10 million transistors in it. If the PC
ever fails, the reason will almost certainly be the mechanical hard drive.
If the power grid fails to provide electricity, the UPS will keep it running
long enough for a graceful shutdown.

In just the last month, we have had a mechanical altimeter fail. The only
way we knew was that it couldn't be set to local field elevation. We had an
airspeed indicator fail to work at all. I had mechanical altimeter suddenly
lose 2000 feet as it became unstuck. The Winter mechanical vario in one
glider spends most of the time stuck at +10 Kts. so we rely on the only
reliable one - the Cambridge L-Nav. (If I ask, "Why the mechanical vario",
I hear, "For backup".) Mechanical instruments are neither rugged nor
reliable.

Mike Borgelt makes an excellent case for using his B40 with it's internal 9V
battery as a backup. Unlike the Winter, it has audio even while running on
the internal battery.

As for readability, I don't think you will find a "three hand" altimeter in
an airliner anymore. They have had drum-type digital displays since
sometime in the 1960's. Many studies have shown the digital readout is
harder to mis-read. Although, today these are likely to be just the back-up
to the digital "glass cockpit".

Bill Daniels

Stefan

August 24th 05, 10:35 PM

Bill Daniels wrote:

> This amazes me. Electricity not reliable? I know this is "conventional
> wisdom" but, I have never had an electronic device fail in flight but many,

I had the battery fail twice on me: During my first 300km flight and
during my second 300km flight. Which meant that I had done two
successful 300km flights without GPS and acoustic vario, but none of
them was logged. :-P

Stefan

Raphael Warshaw

August 24th 05, 10:49 PM

I'll second the use of the B40 as a backup. I don't have a mechanical vario
at all. As a precaution, I change the B40 internal battery on the same
schedule as the one on the MH Oxygen system, wasteful perhaps, but
reassuring.

Ray Warshaw
1LK

"Bill Daniels" > wrote in message
...
>
> "Andreas Maurer" > wrote in message
> ...
>
>> How many times have you praised yourself for having instruments on
>> board that do not need electricity to work properly? :)
>>
>> I did that dozens of times - electricity is definitely not a reliable
>> thing in gliders.
>>
>>
>>
>> Bye
>> Andreas
>
> This amazes me. Electricity not reliable? I know this is "conventional
> wisdom" but, I have never had an electronic device fail in flight but
> many,
> many mechanical instruments have failed me. In fact, even when an
> electronic device seemed to fail, it was always a mechanical switch or
> battery contact that failed and not the device itself. (Hint: Use the
> best
> electrical hardware money can buy.)
>
> I sit here typing on an incredibly complex device called a Personal
> Computer. The CPU alone has over 10 million transistors in it. If the PC
> ever fails, the reason will almost certainly be the mechanical hard drive.
> If the power grid fails to provide electricity, the UPS will keep it
> running
> long enough for a graceful shutdown.
>
> In just the last month, we have had a mechanical altimeter fail. The only
> way we knew was that it couldn't be set to local field elevation. We had
> an
> airspeed indicator fail to work at all. I had mechanical altimeter
> suddenly
> lose 2000 feet as it became unstuck. The Winter mechanical vario in one
> glider spends most of the time stuck at +10 Kts. so we rely on the only
> reliable one - the Cambridge L-Nav. (If I ask, "Why the mechanical
> vario",
> I hear, "For backup".) Mechanical instruments are neither rugged nor
> reliable.
>
> Mike Borgelt makes an excellent case for using his B40 with it's internal
> 9V
> battery as a backup. Unlike the Winter, it has audio even while running
> on
> the internal battery.
>
> As for readability, I don't think you will find a "three hand" altimeter
> in
> an airliner anymore. They have had drum-type digital displays since
> sometime in the 1960's. Many studies have shown the digital readout is
> harder to mis-read. Although, today these are likely to be just the
> back-up
> to the digital "glass cockpit".
>
> Bill Daniels
>
>
>

Ian Strachan

August 24th 05, 11:00 PM

Bill Daniels wrote:

snip

> GPS provides highly accurate, although not ATC compliant, altitude.

I am afraid that the claim that GPS altitude is recorded "highly
accurately" in IGC files from IGC-approved GPS recorders, is
unfortunately not true.

The second part of the statment above IS true, that the GPS altitude
datum is not the same as the pressure altitude datum used worldwide in
aviation for altimeter settings for aircraft separation and for
controlled and restricted airspace.

In theory, due to the angle of cut of the lines-of-position from the
satellites, GPS altitude errors should be, on average, about 1.8 times
those for horizontal position or lat/long. Measurements over many
years by the IGC GNSS Flight Recorder Approval Committee (GFAC) show an
average lat/long error of 11.4 metres, taken from a moving vehicle at
surveyed points at about 51N 001W (Southern England, near Lasham
Gliding Centre). Going on this, an average GPS altitude error could be
expected as about 20.5 metres.

However, in a significant proportion of IGC-format flight data files,
there are significant anomalies in the GPS altitude figures that have
been recorded, in excess of the 20 metres mentioned above. Only today
I was commenting in another email on aspects of an IGC file from a
recent glider flight in the USA that had a 1500 foot overshoot in GPS
altitude (compared to the much more reliably recorded pressure
altitude) for reasons unknown.

The problem seems to be, particularly in low-cost GPS boards, that,
rather than processing a fix in three dimensions, it is processed
separately as lat/long and then separately as altitude. The algorithms
for lat/long and for altitude appear to be different, hence the regular
occurrence in IGC files or GPS altitude anomalies despite few lat/long
anomalies. Naturally, more attention seems to be paid by GPS board
manufacturers to lat/long rather than altitude.

In a survey made in year 2000 after the deliberate Selective
Availability error was removed from the GPS system by Presidential
Decree, no less than 27% of over 400 IGC flight data files analysed
from 7 countries in both hemispheres, had anomaliesof one sort or
another in the GPS altitude recorded in the file. From IGC files that
I have seen since, there is no reason to believe that this proportion
is much improved today. Just look at a large selection of IGC-format
flight data files and see for yourselves. In my database, I have
literally hundreds of IGC flight data files that show major anomalies
in recorded GPS altitude data. Fortunately, anomalies in lat/long data
in the same IGC files are very rare.

This is not an attack on the accuracy of the GPS system or even its
altitude recording capability. It is a reporting of results of GPS
altitude recording in IGC flight data files derived from a number of
low-cost GPS boards made by a number of different companies from
different parts of the world. I guess that in more expensive
"professional aviation standard" GPS boards, and in differential-GPS
systems with local beacons, the GPS altitude figures are more accurate
and with less anomalies. But such (expensive) systems do not apply to
the current 27 types of GNSS flight recorders that are IGC-approved
(from 11 manufacturers) and whose IGC-approval documents appear on the
IGC gliding/gnss web site:

http://www.fai.org/gliding/gnss/igc_approved_frs.pdf

Ian Strachan
Chairman IGC GNSS Flight Recorder Approval Committee

Paul Remde

August 24th 05, 11:08 PM

Hi,

Winter instruments are available with either 6 O'clock or 12 O'clock zero
for airspeed indicators and altimeters. 12 O'clock is standard.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

"Stig Oye" > wrote in message
...
> No. I believe that it is an old German standard, but if you buy
> PZL instruments you can specify it to either top or bottom.
>
> http://www.pzl.com.pl/en/produkty/osprzet_lotniczy/pilotazowo-nawigacyjne/wysokosciomierze/pw-12-a.html
>
> BTW, these instruments are very high quality but somewhat heavy.
> Highly recommended.
>
> Regards Stig Oye
>
> In article >, Roy Bourgeois
> > says:
>>
>>This may be a silly question - but are all metric altimeters
>>configured with 'Zero at 6 O'clock' as I saw in France?
>> I did not have trouble converting to meters/kilometers
>>but I did have trouble quickly reading the altimeter
>>with the zero at the bottom of the instrument face
>>(especially on the little 57mm instruments). Just
>>curious.
>>
>>Roy
>>
>>
>>
>>

Tony Verhulst

August 24th 05, 11:22 PM

Bill Daniels wrote:
> Does it strike some of the digerati here that expensive mechanical
> altimeters with easily mis-read clock-like hands locked into either the
> metric or US measurement systems are archaic?

I have both a mechanical and digital altimeter. When i want to check my
altitude, I tend to rely on the mechanical. Like a watch with hands, I
don'd read it as much as glance at it and I find that easier. YMMV.

Tony V.

Bill Daniels

August 24th 05, 11:47 PM

"Stefan" > wrote in message
...
> Bill Daniels wrote:
>
> > This amazes me. Electricity not reliable? I know this is "conventional
> > wisdom" but, I have never had an electronic device fail in flight but
many,
>
> I had the battery fail twice on me: During my first 300km flight and
> during my second 300km flight. Which meant that I had done two
> successful 300km flights without GPS and acoustic vario, but none of
> them was logged. :-P
>
Stefan, buy a new battery. They are cheap these days. At least, much
cheaper than a failed 300Km attempt.

Bill Daniels

Bill Daniels

August 25th 05, 12:10 AM

By my checking, WAAS enabled, dual antenna DGPS receiver boards are cheap -
on the order of $10US in OEM quantities. The specs say 1 meter RMS in Lat
Long and 6 meters RMS in altitude when a DGPS signal is available. Of
course, they probably aren't in approved loggers.

6 meters in altitude is a lot better than a barometric altimeter on a
non-standard atmospheric day.
I wouldn't want to change ATC's reliance on barometric altimeters. On a
hot day, they understate the real altitude, giving us western US guys
another 1000 or so feet to play in below the floor of Class A airspace.

I checked GPS altitude a couple of times by putting a hand held Garmin GPS
on a prime US Geodetic Survey marker. The marker said 10,346 feet. The GPS
said 10,350 feet + or - 70 feet. The + or - error estimate seemed pretty
pessimistic. Those are pretty typical numbers.

Bill Daniels

"Ian Strachan" > wrote in message
ups.com...
> Bill Daniels wrote:
>
> snip
>
> > GPS provides highly accurate, although not ATC compliant, altitude.
>
> I am afraid that the claim that GPS altitude is recorded "highly
> accurately" in IGC files from IGC-approved GPS recorders, is
> unfortunately not true.
>
> The second part of the statment above IS true, that the GPS altitude
> datum is not the same as the pressure altitude datum used worldwide in
> aviation for altimeter settings for aircraft separation and for
> controlled and restricted airspace.
>
> In theory, due to the angle of cut of the lines-of-position from the
> satellites, GPS altitude errors should be, on average, about 1.8 times
> those for horizontal position or lat/long. Measurements over many
> years by the IGC GNSS Flight Recorder Approval Committee (GFAC) show an
> average lat/long error of 11.4 metres, taken from a moving vehicle at
> surveyed points at about 51N 001W (Southern England, near Lasham
> Gliding Centre). Going on this, an average GPS altitude error could be
> expected as about 20.5 metres.
>
> However, in a significant proportion of IGC-format flight data files,
> there are significant anomalies in the GPS altitude figures that have
> been recorded, in excess of the 20 metres mentioned above. Only today
> I was commenting in another email on aspects of an IGC file from a
> recent glider flight in the USA that had a 1500 foot overshoot in GPS
> altitude (compared to the much more reliably recorded pressure
> altitude) for reasons unknown.
>
> The problem seems to be, particularly in low-cost GPS boards, that,
> rather than processing a fix in three dimensions, it is processed
> separately as lat/long and then separately as altitude. The algorithms
> for lat/long and for altitude appear to be different, hence the regular
> occurrence in IGC files or GPS altitude anomalies despite few lat/long
> anomalies. Naturally, more attention seems to be paid by GPS board
> manufacturers to lat/long rather than altitude.
>
> In a survey made in year 2000 after the deliberate Selective
> Availability error was removed from the GPS system by Presidential
> Decree, no less than 27% of over 400 IGC flight data files analysed
> from 7 countries in both hemispheres, had anomaliesof one sort or
> another in the GPS altitude recorded in the file. From IGC files that
> I have seen since, there is no reason to believe that this proportion
> is much improved today. Just look at a large selection of IGC-format
> flight data files and see for yourselves. In my database, I have
> literally hundreds of IGC flight data files that show major anomalies
> in recorded GPS altitude data. Fortunately, anomalies in lat/long data
> in the same IGC files are very rare.
>
> This is not an attack on the accuracy of the GPS system or even its
> altitude recording capability. It is a reporting of results of GPS
> altitude recording in IGC flight data files derived from a number of
> low-cost GPS boards made by a number of different companies from
> different parts of the world. I guess that in more expensive
> "professional aviation standard" GPS boards, and in differential-GPS
> systems with local beacons, the GPS altitude figures are more accurate
> and with less anomalies. But such (expensive) systems do not apply to
> the current 27 types of GNSS flight recorders that are IGC-approved
> (from 11 manufacturers) and whose IGC-approval documents appear on the
> IGC gliding/gnss web site:
>
> http://www.fai.org/gliding/gnss/igc_approved_frs.pdf
>
> Ian Strachan
> Chairman IGC GNSS Flight Recorder Approval Committee
>
>

Andreas Maurer

August 25th 05, 01:33 AM

On Wed, 24 Aug 2005 15:17:23 -0600, "Bill Daniels"
> wrote:

>This amazes me. Electricity not reliable? I know this is "conventional
>wisdom" but, I have never had an electronic device fail in flight but many,
>many mechanical instruments have failed me.

Glad that you never had a problem. :)
I have lost count of the numbers where my clubs glider's batteries
were forgotten to charge after flight or ran out of energy because
they had reached their service life...

Not to mention more than a couple of GPS failures over the years... :)

Of course - there have been more than a couple of mechanical (Winter)
altimeter failures, too - but at least the altimeter didn't stop
working at all but only lost precision.

It's pretty impossible to convince me of the superiority of something
that needs to be charged as long as more than one owner is involved.
This includes a backup battery. <vbg>

Bye
Andreas

Tim Ward

August 25th 05, 02:41 AM

"Bill Daniels" > wrote in message
...
> Does it strike some of the digerati here that expensive mechanical
> altimeters with easily mis-read clock-like hands locked into either the
> metric or US measurement systems are archaic?
>
> GPS provides highly accurate, although not ATC compliant, altitude.
Various
> vendors provide electronic pressure altimeters with digital displays that
> can be switched between meters and feet with the push of a button.
Digital
> pressure altitude sensors drive the "glass cockpits" of new GA aircraft.
>
> I seems to me that clock-like altimeters designed 70 years ago and
> maintained by watchmakers must be nearing their well-deserved retirement.
>
> Bill Daniels
>
Yeah, now if they can just make them so they don't need batteries.

Tim Ward

Bill Daniels

August 25th 05, 03:45 AM

"Tim Ward" > wrote in message
ink.net...
>
> "Bill Daniels" > wrote in message
> ...
> > Does it strike some of the digerati here that expensive mechanical
> > altimeters with easily mis-read clock-like hands locked into either the
> > metric or US measurement systems are archaic?
> >
> > GPS provides highly accurate, although not ATC compliant, altitude.
> Various
> > vendors provide electronic pressure altimeters with digital displays
that
> > can be switched between meters and feet with the push of a button.
> Digital
> > pressure altitude sensors drive the "glass cockpits" of new GA aircraft.
> >
> > I seems to me that clock-like altimeters designed 70 years ago and
> > maintained by watchmakers must be nearing their well-deserved
retirement.
> >
> > Bill Daniels
> >
> Yeah, now if they can just make them so they don't need batteries.
>
> Tim Ward
>

What's the big deal with batteries? IMHO, batteries are at worst a minor
inconvenience easily worth enduring for the benefits of the technology they
make possible.

Every portable gadget uses them. Most folks have a cell phone, PDA,
portable GPS, digital camera, maybe a camcorder and who knows what else.
Even your car, tug or winch won't start without a battery. They're cheap
and they work fine with a little TLC and regular replacement.

My glider uses a standard 7.5 AH 12V SLA that now sits on a shelf connected
to a charger that quietly maintains the charge. I know for sure that it
will work at least 10 hours and still show more than 12.5 volts while
transmitting. It has a three year "replace by" date written on it whereupon
I will plunk down $20 for another at "Batteries-R-Us" even if it still seems
OK. I don't trust old batteries.

Bill Daniels

Bert Willing

August 25th 05, 08:43 AM

Well, even if there is only one owner involved, I'm not going to rely on
electrically power instruments only. Never.

--
Bert Willing

ASW20 "TW"

"Andreas Maurer" > a écrit dans le message de news:
...
> On Wed, 24 Aug 2005 15:17:23 -0600, "Bill Daniels"
> > wrote:
>
>
>>This amazes me. Electricity not reliable? I know this is "conventional
>>wisdom" but, I have never had an electronic device fail in flight but
>>many,
>>many mechanical instruments have failed me.
>
> Glad that you never had a problem. :)
> I have lost count of the numbers where my clubs glider's batteries
> were forgotten to charge after flight or ran out of energy because
> they had reached their service life...
>
> Not to mention more than a couple of GPS failures over the years... :)
>
> Of course - there have been more than a couple of mechanical (Winter)
> altimeter failures, too - but at least the altimeter didn't stop
> working at all but only lost precision.
>
>
> It's pretty impossible to convince me of the superiority of something
> that needs to be charged as long as more than one owner is involved.
> This includes a backup battery. <vbg>
>
>
>
> Bye
> Andreas

Andreas Maurer

August 25th 05, 12:47 PM

On Thu, 25 Aug 2005 09:43:46 +0200, "Bert Willing"
> wrote:

>Well, even if there is only one owner involved, I'm not going to rely on
>electrically power instruments only. Never.^

I still remember one competition back in 1991 when the US shut down
GPS and suddenly a gaggle of 30 standard class gliders lost their
navigation in the vicinity of Sobernheim (several airbases and
restricted airspace there). I got to know a new definition of the term
"confusion".

Bye
Andreas

Tim Ward

August 25th 05, 03:37 PM

"Bill Daniels" > wrote in message
...
>
> "Tim Ward" > wrote in message
> ink.net...
> >
> > "Bill Daniels" > wrote in message
> > ...
> > > Does it strike some of the digerati here that expensive mechanical
> > > altimeters with easily mis-read clock-like hands locked into either
the
> > > metric or US measurement systems are archaic?
> > >
> > > GPS provides highly accurate, although not ATC compliant, altitude.
> > Various
> > > vendors provide electronic pressure altimeters with digital displays
> that
> > > can be switched between meters and feet with the push of a button.
> > Digital
> > > pressure altitude sensors drive the "glass cockpits" of new GA
aircraft.
> > >
> > > I seems to me that clock-like altimeters designed 70 years ago and
> > > maintained by watchmakers must be nearing their well-deserved
> retirement.
> > >
> > > Bill Daniels
> > >
> > Yeah, now if they can just make them so they don't need batteries.
> >
> > Tim Ward
> >
>
> What's the big deal with batteries? IMHO, batteries are at worst a minor
> inconvenience easily worth enduring for the benefits of the technology
they
> make possible.
>
> Every portable gadget uses them. Most folks have a cell phone, PDA,
> portable GPS, digital camera, maybe a camcorder and who knows what else.
> Even your car, tug or winch won't start without a battery. They're cheap
> and they work fine with a little TLC and regular replacement.
>
> My glider uses a standard 7.5 AH 12V SLA that now sits on a shelf
connected
> to a charger that quietly maintains the charge. I know for sure that it
> will work at least 10 hours and still show more than 12.5 volts while
> transmitting. It has a three year "replace by" date written on it
whereupon
> I will plunk down $20 for another at "Batteries-R-Us" even if it still see
ms
> OK. I don't trust old batteries.
>
> Bill Daniels
>

Upon reflection, Bill, I'm sure that an instrument could be built that could
satisfy both of us.
Digital, easily scalable, there's no reason it can't have both an analog
display (or quasi-analog, with LCD) for trends, and a 5 digit display for
accuracy. It could have a lithium cell recharged by the expansion and
contraction of an aneroid . Several "perpetual clocks" have used that
scheme to drive mechanical gear trains with far smaller pressure changes
than you'll get going up and down in a glider or airplane.
An update rate of twice a second should be plenty fast enough. With LCDs,
and CMOS circuitry running a few microamps at two volts or so, it's probably
not impossible to build. You could probably build one with a primary lithium
battery that would only need to be changed once every ten years or so.
That would be the cheapest way to go.
What will it cost to get it approved? How many people are going to buy it?
In the small market that is aviation, what will it cost to build? If you
could sell it cheaper than a mechanical altimeter, you might have a shot.
In enough volume, you might be able to do that. I don't know if the
altimeter market is large enough for that to be possible. The combined
output of all the altimeter manufacturers is probably not as big as a run
of, say, a cheap DVD player.

I dunno. I'm afraid good enough is the enemy of best.

If you don't care whether or not it's approved, or whether it takes
batteries, then you should look at the Flytec hang glider varios. They have
a lot of options as to what they display and how they display it, and I
believe they'll display altitude both digitally and analog. They'd take up
a bit more space on a panel, though.

Tim Ward

[email protected]

August 25th 05, 08:23 PM

I have to fall firmly and loudly into the "digital is good, electrical
insturments can be reliable, mechanical varios belong in museums"
group.

I would love to see a serious study that shows that classic analog
airspeed and altimeters (as used in gliders) are easier to read and
less susceptible to misinterpretation than a properly designed (but
unfortunately, theoretical) replacement digital airspeed and altimeter.
With the advent of Head-up-Displays (HUDs), fighter planes have moved
to almost completely digital displays of most values - only those where
trend is crucial, such as vertical velocity and radar altitude,
continue to have a companion analog display. Otherwise, its a straight
number, usually rounded off to the nearest knot and 10 feet. Works
fine in an F-15E, should work pretty good in an LS6

By comparison, trying to interpret a three-needle altimeter is like
trying to read sanskrit! And then there are 1 1/2 revolution airspeed
indicators!

If you have a PDA in your cockpit, try setting it up to have a nice big
font altitude (and speed, if available) display on it and try it - you
might find that it is really easy to glance at and read.

I have two seperated battery systems, and no mechanical vario. I'm
stuck with a "steam-gauge" airspeed indicator and altimeter, but what I
would really like is a digital airspeed, digital altimeter, and an
accurate AOA indicator. For tradition, I'll keep the vario needles -
since there I'm looking for trend (to provide a value to the audio),
and read a digital averager for real decision making.

Heck, last year I took off on a fine day only to find my airspeed inop
(bug in the pitot) - but that didn't prevent me from flying a nice
little 500+ k XC with some friends of mine. The only time I really
missed the airspeed indicator was in the pattern. Just flew it a bit
faster than usual (that AOA indicator sure would have been nice to have
then...).

Now the huge caveat - this is all fine in a private ship - I don't see
how a the average club ship would manage.

Kirk
66

Robin Birch

August 25th 05, 09:02 PM

In message . com>,
writes
>I have to fall firmly and loudly into the "digital is good, electrical
>insturments can be reliable, mechanical varios belong in museums"
>group.
>
Must admit that my beliefs are: Digital is good - for somethings - bad
for others - analogue is good - for somethings - bad for others.

Digital is very good for getting absolutes - fly at a particular flight
level - a specific temperature - or a rate of something. Analogue is
very good for trends and similar, horses for courses. Most of what we
do flying we just want a trend or rough peak - analogue - say (in my
personal opinion) thermal centering.For saying that a particular thing
is better or good enough, say is that thermal good enough to stay with
or is it falling off so we want to go to another, digital in the form of
an averager is the absolute best.

We don't need absolute altitude in an altimeter. Flight Levels are in
500 ft increments. We do absolutes in loggers.

Mechanical can break so can electric. You can get many more functions
out of electric which is good. However I am fully in favour of separate
and different technology systems in case something goes pop.

My own experience in club equipment is that electric goes wrong many
times more often than mechanical and it is far easier to get a poorly
installed mechanical system working than an electronic.

>I would love to see a serious study that shows that classic analog
>airspeed and altimeters (as used in gliders) are easier to read and
>less susceptible to misinterpretation than a properly designed (but
>unfortunately, theoretical) replacement digital airspeed and altimeter.
> With the advent of Head-up-Displays (HUDs), fighter planes have moved
>to almost completely digital displays of most values - only those where
>trend is crucial, such as vertical velocity and radar altitude,
>continue to have a companion analog display. Otherwise, its a straight
>number, usually rounded off to the nearest knot and 10 feet. Works
>fine in an F-15E, should work pretty good in an LS6
>
Well known fact, much publicised by the ergonomicist who sits next to
me, is that three needle altimeters are pure trouble from a reading
point of view. ASIs are less prone to missreading but it does happen.
(She once borrowed one of mine for a lecture on the fact).

Very fast ships (F15s and the like couldn't use foot or even hundred
foot needles as they would spin so fast that they would fall off) need
different technology. Actually, the best (from my opinion) ASI was the
one used in the lightning which was a horizontal tape that wound across
the top of the instrument panel.

They are using analogue in the same way that we are but the low values
are inappropriate. For this they use digital which is easier to control
at fast fates of change.

As you say they are using needles for trends, we do the same. I kinda
think that to do our job properly we need both (needle and digital), the
argument between electric and mech is different but again I think we
need both from a safety point of view.

>By comparison, trying to interpret a three-needle altimeter is like
>trying to read sanskrit! And then there are 1 1/2 revolution airspeed
>indicators!
>
>If you have a PDA in your cockpit, try setting it up to have a nice big
>font altitude (and speed, if available) display on it and try it - you
>might find that it is really easy to glance at and read.
>
And see what happens when the software goes pling which happens with
even the best systems.

>I have two seperated battery systems, and no mechanical vario. I'm
>stuck with a "steam-gauge" airspeed indicator and altimeter, but what I
>would really like is a digital airspeed, digital altimeter, and an
>accurate AOA indicator. For tradition, I'll keep the vario needles -
>since there I'm looking for trend (to provide a value to the audio),
>and read a digital averager for real decision making.
>
>Heck, last year I took off on a fine day only to find my airspeed inop
>(bug in the pitot) - but that didn't prevent me from flying a nice
>little 500+ k XC with some friends of mine. The only time I really
>missed the airspeed indicator was in the pattern. Just flew it a bit
>faster than usual (that AOA indicator sure would have been nice to have
>then...).
>
>Now the huge caveat - this is all fine in a private ship - I don't see
>how a the average club ship would manage.
>
>Kirk
>66
>
Robin
--
Robin Birch

Don Johnstone

August 25th 05, 09:06 PM

The digital/analog argument was put to me thus. A digital
watch tells you what time it is, an analog watch tells
you what time it isn't as well. The same applies to
analog instruments, in the case of the ASI it tells
you your speed if you study it and at a glance if you
are above or below your target. It's a question of
what you need to know. Digital needs study and calculation,
analog is instant.

At 19:24 25 August 2005, wrote:
>I have to fall firmly and loudly into the 'digital
>is good, electrical
>insturments can be reliable, mechanical varios belong
>in museums'
>group.
>
>I would love to see a serious study that shows that
>classic analog
>airspeed and altimeters (as used in gliders) are easier
>to read and
>less susceptible to misinterpretation than a properly
>designed (but
>unfortunately, theoretical) replacement digital airspeed
>and altimeter.
> With the advent of Head-up-Displays (HUDs), fighter
>planes have moved
>to almost completely digital displays of most values
>- only those where
>trend is crucial, such as vertical velocity and radar
>altitude,
>continue to have a companion analog display. Otherwise,
>its a straight
>number, usually rounded off to the nearest knot and
>10 feet. Works
>fine in an F-15E, should work pretty good in an LS6
>
>By comparison, trying to interpret a three-needle altimeter
>is like
>trying to read sanskrit! And then there are 1 1/2
>revolution airspeed
>indicators!
>
>If you have a PDA in your cockpit, try setting it up
>to have a nice big
>font altitude (and speed, if available) display on
>it and try it - you
>might find that it is really easy to glance at and
>read.
>
>I have two seperated battery systems, and no mechanical
>vario. I'm
>stuck with a 'steam-gauge' airspeed indicator and altimeter,
>but what I
>would really like is a digital airspeed, digital altimeter,
>and an
>accurate AOA indicator. For tradition, I'll keep the
>vario needles -
>since there I'm looking for trend (to provide a value
>to the audio),
>and read a digital averager for real decision making.
>
>Heck, last year I took off on a fine day only to find
>my airspeed inop
>(bug in the pitot) - but that didn't prevent me from
>flying a nice
>little 500+ k XC with some friends of mine. The only
>time I really
>missed the airspeed indicator was in the pattern.
>Just flew it a bit
>faster than usual (that AOA indicator sure would have
>been nice to have
>then...).
>
>Now the huge caveat - this is all fine in a private
>ship - I don't see
>how a the average club ship would manage.
>
>Kirk
>66
>
>

Don Johnstone

August 25th 05, 09:31 PM

At 22:06 24 August 2005, Ian Strachan wrote:

snip

>Bill Daniels wrote:
>
>snip
>
>> GPS provides highly accurate, although not ATC compliant,
>>altitude.
>
>I am afraid that the claim that GPS altitude is recorded
>'highly
>accurately' in IGC files from IGC-approved GPS recorders,
>is
>unfortunately not true.
>

>
>This is not an attack on the accuracy of the GPS system
>or even its
>altitude recording capability. It is a reporting of
>results of GPS
>altitude recording in IGC flight data files derived
>from a number of
>low-cost GPS boards made by a number of different companies
>from
>different parts of the world. I guess that in more
>expensive
>'professional aviation standard' GPS boards, and in
>differential-GPS
>systems with local beacons, the GPS altitude figures
>are more accurate
>and with less anomalies. But such (expensive) systems
>do not apply to
>the current 27 types of GNSS flight recorders that
>are IGC-approved
>(from 11 manufacturers) and whose IGC-approval documents
>appear on the
>IGC gliding/gnss web site:
>
>http://www.fai.org/gliding/gnss/igc_approved_frs.pdf

The truth is that it is possible to record altitude
very accurately with GPS, suyveyors who produce our
maps use GPS both for lat/long and elevation with a
resolution in height of less that 15mm over 10Km. Perhaps
the reason that the manuafacturers mentioned above
do not upgrade their equipment is that there is no
demand as the IGC refuse to consider using GPS altitude.
However good a baro recorder is it can never approach
the accuracy of GPS.

Martin Gregorie

August 25th 05, 10:01 PM

On Thu, 25 Aug 2005 21:02:37 +0100, Robin Birch wrote:

> In message . com>,
> writes
>>I have to fall firmly and loudly into the "digital is good, electrical
>>insturments can be reliable, mechanical varios belong in museums" group.
>>
> Most of what we do
> flying we just want a trend or rough peak - analogue - say (in my personal
> opinion) thermal centering.For saying that a particular thing is better or
> good enough, say is that thermal good enough to stay with or is it falling
> off so we want to go to another, digital in the form of an averager is the
> absolute best.
>
Agree 100% I really like the vario display on an SDI C4 and a Tasmin
V1000 vario. Both use analogue for instant reading and digits for the
averager. Both are easy to use.

OTOH what are you doing looking at the vario in a thermal :-)
I find the sound from a C4 makes centring very easy and all I look at
is a glance at the averager from time to time to see if its time to leave
the thermal yet.

I very much like the idea of a B.40 as backup vario because it has its own
internal battery and switch-over circuitry. I just wish it used an LCD
analogue display rather than a needle for the instant rate display.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Robin Birch

August 26th 05, 05:41 PM

In message >, Martin
Gregorie > writes
>On Thu, 25 Aug 2005 21:02:37 +0100, Robin Birch wrote:
>
>> In message . com>,
>> writes
>>>I have to fall firmly and loudly into the "digital is good, electrical
>>>insturments can be reliable, mechanical varios belong in museums" group.
>>>
>> Most of what we do
>> flying we just want a trend or rough peak - analogue - say (in my personal
>> opinion) thermal centering.For saying that a particular thing is better or
>> good enough, say is that thermal good enough to stay with or is it falling
>> off so we want to go to another, digital in the form of an averager is the
>> absolute best.
>>
>Agree 100% I really like the vario display on an SDI C4 and a Tasmin
>V1000 vario. Both use analogue for instant reading and digits for the
>averager. Both are easy to use.
>
>OTOH what are you doing looking at the vario in a thermal :-)
Flying club K8s that I keep forgetting to put the battery in and so the
mechanical is all I've got or my Astir when I've forgotten to charge
them and they've gone flat on me after 4 hours :-))

>I find the sound from a C4 makes centring very easy and all I look at
>is a glance at the averager from time to time to see if its time to leave
>the thermal yet.
>
>I very much like the idea of a B.40 as backup vario because it has its own
>internal battery and switch-over circuitry. I just wish it used an LCD
>analogue display rather than a needle for the instant rate display.
>

--
Robin Birch