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
|