(Snowbird) wrote
say something to the effect of well, I've had a gyro failure in
actual and it was no big deal so contrary to popular opinion I
don't think it's something a proficient pilot needs to sweat
about. (I paraphrase here, and perhaps that wasn't the message
you intended to convey, but it's the message I and, I think,
others, have garnered from your posts)

No, that's basically the message. I don't think it's something a
proficient pilot needs to really sweat. Sure, it could get you - but
it probably won't. I consider it comparable to an engine failure in a
twin after reaching blue line and gear up - it's something you train
for, and if you've trained for it it's not going to be a big deal when
it happens. BTW, I've had that as well, and it wasn't a big deal
either.

That's why I think the distinction between a single instrument
failure, and vacuum failure (loss of two instruments) may be
relevant to point out.

Yes, I think it's VERY important. An analogous situation might be a
stuck valve vs. a total engine failure. In your average light single,
a stuck valve means you're not going to make enough power to climb -
but you will have enough to flatten your glideslope and increase the
options. Therefore, the situation is easier than a total failure. By
the same token, a vacuum failure when established in level cruise is
going to be easier to handle than one on climbout while getting an
amended clearance. No two situations are ever the same - we normally
practice for the worst case.

What makes vacuum failure (as opposed to single gyro failure) ugly is
that two out of three gyros fail (in a typical setup). Of course
that's going to make the situation more difficult. Essentially you're
set up so that a single point failure takes out two important
instruments. I used to fly a TriPacer where it was worse - all three
gyros were vacuum powered. Believe it or not, this is legal - but I
doubt too many pilots could survive a vacuum failure in IMC in that
airplane. Of course it was a wet pump, which is, if my experience and
the experience of the people I know is any guide, more reliable than
the engine that drives it. That airplane, early in its history, was
IFR equipped (to 1950's standards) and was used as a cargo hauler. I
wonder if the pilot knew all his gyros were on one pump.

Anyway, my point is that dual simultaneous failures are more difficult
to handle than individual failures and a proper design won't allow
them to occur with any regularity. Two gyros driven by a single dry
pump does not constitute proper design. That doesn't make it
unflyable, even in IMC, but given the ready availability of wet pumps
for all the popular engines in use on light singles, it's pretty
stupid. Kind of like flying IFR without a handheld GPS - it's doable,
and it was done for years, but given how useful they are and how
little they cost, it's pretty dumb not to have one.

My gyro failure situation included only the AI, but on the other hand
it happened during the highest workload phase of flight. Would it
have been more difficult had I lost the DG as well? Certainly.
Dangerous? I doubt it. Handling the AI loss was just too easy, and
doing night hood work with both out isn't all that difficult either.

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.

Actually, I'm glad to hear you say this. The impression that
I've received from your previous posts is that you believed a
vacuum failure should be no big deal at all to a proficient pilot.

An engine failure over an airport should also be no big deal at all to
a proficient pilot. That doesn't mean I'm willing to take off when
the oil pressure at idle is well above top redline - even if I'm never
going to be out of glide range of the field (and yes, this was a real
situation).

If the cause of accidents
following vacuum or gyro failure is lack of proper, recurrant
training, why not just invest in training instead of redundant
instrumentation or vacuum sources--isn't that what you've
suggested in the past when the point has been raised?

Well, in my opinion the sensible thing to do is to replace the dry
pump with a wet one - given that it's probably more reliable than the
engine that drives it, that's certainly the reasonable and
cost-effective solution in a single engine airplane. But over and
above that - yes, I think recurrent training is preferable to
redundant instrumentation for this.

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.

That's certainly true for me.

And that has a lot to do with the kind of airplanes you've flown and
the way they were equipped. In my airplane, I miss the AI more than I
miss the DG. My understanding is that in a jet, loss of all attitude
indicators in IMC is certain death.

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.

Apples and oranges to the topic under discussion here, which was
whether the "ugly outcomes" of vacuum failure are entirely due
to improper training.

Unless I'm missing something, there is no requirement that an
IPC necessarily include partial panel work,

You're missing something. What you say used to be true, but no longer
is. These days, an ICC must consist of "a representative number of
tasks required by the instrument rating practical test" and when you
look at the instrument rating PTS, those tasks are spelled out.
Partial panel approaches (and single engine approaches for twins) are
required.

Michael