Actually, Ron you can derive a very accurate attitude reference from only
accelerometer(s).

This is how the AHRS units in a Garmin G1000 work for example. They
integrate accelerations and moments
using small very accurate mechanical sensors. There is no "spinning"
platform which uses rigidity in space to
provide a reference on these airplanes, except for the backup AI.

The reason your brain is fooled is becuase it uses a fluid pool to sense the
vertical. In the case of an acceleration
the fluid shifts and you mis-interpret this as a change in attitude.

Now, I cannot vouch for using a camera as an inflight reference :^)
However, I have wondered if some sort of
"solid state" package (or something based on the small RC helicopter gyros)
could be built that could provide
an attitude reference that you could even velcro to the glare shield. Maybe
the camera is proof we would be close.

Regards
Todd

"Ron Garret" wrote in message
...

It is most unfortunate that they chose an aviation-style display because
this feature is almost certainly implemented with an accelerometer, not
a gyro, so it will not work in an airplane. It will be fooled in
exactly the same way that the human inner-ear is fooled, which is the
reason you need a gyro-based AI (or TC) in the first place. If you try
to use this as a backup AI in IMC you will almost certainly die.

rg