On 13-Jul-2003, Ray Andraka wrote:

The problem isn't just finding a home for it, it is finding a home for it
that is in a spot where it will be in the pilot's primary scan. I don't
think
it would do much good on the other side of the panel where it might only
be
referenced once a minute or less.


Our Arrow has a backup electric AI on the right side of the panel. It is
turned on whenever I am in or near IMC. I do not include it in my primary
instrument scan, but check it periodically to make sure it is on and stable.
I have fortunately never had a failure of my vacuum AI in IMC, but I have
practiced under the hood with the vac AI and DG covered, using the electric
AI for guidance. For me, it only takes a few seconds to get comfortable
with looking across the panel, and sure beats sweating bullets trying to
hold attitude and a reasonable course with only the TC, particularly in
turbulence.

So, the only issue is whether I could detect a failed vac AI before it leads
me (or the autopilot) into an unusual attitude. If the problem is (as is
most likely) a vacuum pump failure, I have a vacuum warning light right in
front of my eyes that would be hard to miss. But a failure of the gyro
itself could be trickier. I tell myself that if I can't keep a reasonable
course (per the DG) with a wings-level attitude (per the AI), then something
is wrong and I need to immediately refer to the TC and the electric AI to
sort things out.

-Elliott Drucker