(Snowbird) wrote
One observation from the recent ASF/FAA vacuum failure study
was that pilots who lost only their AI (electric HSI did not
fail) did not lose control of the airplane, while a significant
number of pilots (same aircraft) lost control when they lost
both. There was no correlation to time in type or total time.

This result suggests to me that it might be a mistake to
extrapolate from "lose AI no problem" to "lose gyros no
problem".

That's somewhat valid. I don't worry about this situation for two
reasons: First, I have dual vacuum pumps, so loss of both gyros
simultaneously is very, very unlikely. The same is true of a wet pump
setup. I've already made my feelings about flying IMC with a single
dry pump and no backups well known, but in case anyone missed it -
it's stooopid. Second, my GPS has an HSI mode.

The reason I say it's somewhat valid is this - my (admittedly somewhat
limited) experience as an instrument instructor is that most people
miss having the DG a lot more than they miss having the AI. While
there is a case to be made that a jet can't be flown without an AI (no
jet crew that lost all attitude indicators in IMC has ever survived)
light piston airplanes most certainly can be.

There are currently no "real stats" which prove or disprove
the contention that this ugliness is entirely due to improper
training.

No, but that's the way to bet. It's certainly how my insurance
company is betting - I'm now required to take a full IPC with engine
cuts every year in make and model, regardless of recency of
experience, if I want to keep my relatively low rates.

Michael