Backup gyros - which do you trust?

"Sydney Hoeltzli" wrote in message
...
Michael wrote:

2) since 2 AIs weren't enough to keep the plane upright (combined
with 2 turn and banks, 2 of every other instrument), require
passenger planes to have 3

Yes, that's the recommendation. IMO it's unmitigated crap. First
off, AI's should not be failing at an average of less than 300 hours.
Second, there were still two good PNI's (basically HSI's) and
turn&slip indicators. But could the pilots use them? Probably not
because "This technique, commonly referred to as 'limited panel' (see
paragraph 1.5.3.2) does not form part of a professional pilot's
recurrency training and testing."

You Have Got To Be Kidding.

Are you serious? Yes, I missed that. Are they asserting this
shocking hole in proficiency training is widespread?

I think you're barking up the wrong tree here. Classic teaching of
partial/limited panel involves covering an instrument and then continuing to
fly without it. In the case of the Bandeirante accident, that wasn't the
issue. There was still a perfectly serviceable AI in the panel, and a pilot
sitting in front of it. The issue was identifying the failed instrument in a
complex cockpit environment.

The chances of being left with no working AI in the panel of a transport
aircraft (which starts with 3 AIs) but still having the instrumentation to
fly partial panel are so remote that it's not worth the time to train on it.
That time is better spent on other exercises, one of them *recognition* of
instrument failure.

For GA aircraft the situation is different. The probability of ending up
with a TC but no AI is much higher, and controlling the aircraft
successfully without it is easier. That makes it well worth the practice.

Julian Scarfe