Solid State Gyro

[PaulH]

Is it possible to legally retrofit a panel-mount solid state AI to an
old aircraft? Seems to me this the shape of things to come in the
gyro backup game.

There appear to be pocket computer versions available also - any
thoughts on using velcro to park one of these on the panel for
emergency use? (Excuse me, hook and loop - musn't get sued for
trademark infringement).

[Ben Jackson]

In article >,
PaulH > wrote:
>Is it possible to legally retrofit a panel-mount solid state AI to an
>old aircraft? Seems to me this the shape of things to come in the
>gyro backup game.

I've been playing with one of the Analog solid state gyros. I want to
build a small combination TC + "DG" instrument (no absolute heading, but
you could think of it as automating a timed turn). A single gyro is
just *barely* stable enough (with multi-point temperature calibration
for each individual chip) to provide a heading reference alone. It's
easily stable enough to provide a TC-like display. I think most of the
commercial units you'll see will be 3-axis gyro/accelerometer combos
(like Control Vision's system) which can self-calibrate (and for that
matter automatically "erect" even without being perfectly square to the
airframe) by using the accelerometers as a long-term stable reference.

--
Ben Jackson
>
http://www.ben.com/

[James M. Knox]

(Ben Jackson) wrote in
news:oQjac.138439$_w.1599417@attbi_s53:

> I've been playing with one of the Analog solid state gyros. I want to
> build a small combination TC + "DG" instrument (no absolute heading,
> but you could think of it as automating a timed turn). A single gyro
> is just *barely* stable enough (with multi-point temperature
> calibration for each individual chip) to provide a heading reference
> alone. It's easily stable enough to provide a TC-like display. I
> think most of the commercial units you'll see will be 3-axis
> gyro/accelerometer combos (like Control Vision's system) which can
> self-calibrate (and for that matter automatically "erect" even without
> being perfectly square to the airframe) by using the accelerometers as
> a long-term stable reference.

I made one up in the lab a few years ago. Interesting experiment, but
there was no way to get it certified (without so much extra stuff that
the basic gyro would have to sell for around the $3K+ range). The
problems are pretty much what you have already figured out.

o Temperature drift.
o Integration error
o Non-static erection (no jokes, please <G>)

The temperature drift can be helped by characterizing each unit. Long
term integration error is the biggest problem. Most of the Control
Vision type systems "fake it" by assuming you are usually flying
straight and level. So whatever you do long enough becomes straight and
level. [Real AH's have the same problem, but at the time the FAA would
not accept "equivalent level of safety" certification.]

The non-static erection problem still exists, of course. That's why
most of the new glass cockpit systems have a requirement that the plane
remain level (and usually stationary) for several minutes after startup.
A "hiccup" in flight, where the system has to re-initialize itself, is a
real problem if you are not currently straight and level.

Still, I think it could be a big help in an emergency. Just wasn't
possible to convince the FAA.

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
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