Sydney Hoeltzli wrote:

No, I don't think so. He states seperately that his vacuum instruments
tumbled, and gives the reason. Then he assumes the reader remembers
this, later on.

I'm afraid not! The word 'tumble' does not even appear in this story. But
anyway, perhaps you read another account where the author was more specific.


Really? It's clear to me. He was flipped inverted, and his gyros
tumbled. Are you sure you read it?

I'm sure. He says he 'flipped' (I guess he must mean 'rolled') and that 'just
about every instrument [was] gone for the time being." That's it. Maybe you
read another account with more detail. I do not make any assumption about why
or when his gyros tumbled, or even that they tumbled. Guess I've become
careful after reading accident synopses. Additionally, I've rolled airplanes
with gyros - in my experience the gyros tumble, re-erect, and that's that. So
there's definitely a lot missing from the story that the reader has to fill in
for himself with guesses.


I think you missed the point, which is to correlate engine noise
with yoke movement. If you pull back the yoke to climb, but engine
noise increases, what does that tell you? If you push forward
on the yoke but engine noise decreases, what does that tell you?
(recall we're talking fixed pitch prop here)

Actually, I think I got it. Start the plane in level inverted flight, try
your yoke exercise and see what it tells you. I'm not saying it can't be used
when you know you're not inverted, but if the airplane's attitude is a true
unknown to the pilot, such a method can only be used in the correlative sense.



If your gyros tumbled because you flipped inverted and your pressure
instruments were temporarily unreliable because of massive pressure
changes, what would you suggest as the "best guide" to determining
if you're inverted?

Hmm. Maybe this is another area where we're not thinking about the same
thing. Exactly where in this story does the author suffer a 'massive pressure
change'? What caused the pressure instruments to 'become unusable?' There've
been studies conducted in which the pilot, given instrument failures in a
controlled environment (or simulator) thought that other instruments had
failed and didn't believe the associated indications of the instruments that
actually worked. Could it be possible that this is the case here? Again, why
would the pressure instruments become unusable?


Have you tried what Big John suggested, taking the AIs loose from
the panel and seeing if/when they tumble, and when (after how much
banking and diving) they develop sufficient error to be problematic
as guides?

Heck no. I pamper the gyros. Have replaced one already, don't want to
replace any more any time soon!


Hmmmm...if the issue of having to turn one's head frequently is
just a proficiency thing, Ryan, and any pilot ought to be able
to handle it if he flies with a safety pilot enough -- why do
some experienced pilots stress that the scan should involve just
moving the eyes, not the head?

For those who more easily become disoriented, keeping the head 'still' does
help. When you graduate to a twin with a panel full of instruments left to
right, or a business jet... you simply have to be able to do it. Of course
by the time many pilots fly jets their scan is quite good anyway.


Why do physiologists stress that rapid head movements are a good
way to induce spatial disorientation?

There's a difference between breakdancing in the cockpit and making a full
scan of all the instruments, Sydney. You do what you have to do.

-Ryan
CFI/MEI/CFI-H
(testing new signature)