The trutrak has built in magnetometer for backup source of heading in case
of GPS signal loss.
Kevin
----- Original Message -----
From: "Frans Veldman" <frans@paardnatuurlijk.nl>
Sent: Monday, March 09, 2009 3:58 PM
Subject: Re: Europa-List: 3 phase 115V AC 400Hz light weight power supply
> <frans@paardnatuurlijk.nl>
>
> ALAN YERLY wrote:
>> Frans,
>> The Tru Track ADI Pilot Attitude indicator is $1000 and comes with
>> internal compass and ball which is great.
>
> As far as I know it is not a compass but a GPS heading indicator. I
> alread have a GPS, a compass is these days meant as a backup for the GPS
> (in case of satellite failure). A "compass" based on GPS is worthless as
> it offers almost no extra redundancy.
> And as I mentioned before, solid state gyro's still have so much drift
> that they need contineous compensation. Solid state gyro's are good in
> detecting sudden changes, but they can't detect whether a situation
> persists. So they need compensation from GPS ("hey we are still turning,
> so we are most likely still banking) and from the static port ("pressure
> is still decreasing, so let's continue to display a pitch-up, that would
> probably be right"). These things are thus not showing the actual
> situation, but a *derived* situation. Which will probably be right most
> of the time, but offers you no additional information and is worthless
> in a case of emergency: Loose your static port for some reason (icing?),
> and you will loose your "pitch indicator" as well. Loose the GPS signal
> for some reason, and the "compass" is gone too. Bank your airplane
> without making a turn, and the indicator will try to convince you that
> the wings are really, really level. (Don;t believe me? Try it next time
> yourself. Of course you won't intentionally maintain heading with a
> banked plane in VMC (cross controlled), but it could easily happen in
> IMC, and that's why we have this attitude indicator in the first place,
> right?). Problem with all this is lack of redundancy, and it is the
> redundancy why I want to have an attitude indicator and compass in the
> first place.
>
>> Add a servo in the ADI Pilot I and you have
>> autopilot or (wing leveler) that interfaces with any Garmin product and
>> most others.
>
> Here the same story. One of the reasons I have an auto-pilot is if I
> inadvertently fly into IMC. If I suspect that my attitude indicator is
> failing, I will let the autopilot take over. Or the other way around.
> Unless.... the autopilot is linked to the same failing attitude
> indicator. Loose that single one instrument, and all your options are
> gone.
>
>> Had a Falcon, had a Ray Allen, they all fail over time. Tru Track is
>> solid state reliable, light and uses less power.
>
> It certainly has some advantages. But it is still not an equal
> substitute for a real gyro.
>
> --
> Frans Veldman
>
>
>
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