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recovery from inverted IMC (a propos of "backup gyros" thread)



 
 
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  #1  
Old July 14th 03, 02:24 PM
Sydney Hoeltzli
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Default recovery from inverted IMC (a propos of "backup gyros" thread)

Because I think this is a story worth hearing, I'm posting
this link here as well as in the original thread, where
people who've stopped reading might miss it.

http://makeashorterlink.com/?Z27312245

If you don't like makeashorterlink, go to groups.google.com
and search rec.aviation.student in 1999 for "all the words"
pet grumman

This happened in Australia in the mid to late '90s -- '96
to '98, somewhere about there. It was originally posted
on the Grumman Gang, and reposted to USENET with the author's
written permission.

I think it is well worth reading, especially for those who
seem to feel the tach and the T/C are superfluous.

The bottom line is: there are circumstances one might plausibly
encounter where the only reliable instruments in the cockpit
may be the tachometer, the turn coordinator, and the pilot's
hearing.

One might wish to consider this when determining whether to
move the tach and TC outside the primary scan.

Cheers,
Sydney

  #2  
Old July 14th 03, 04:01 PM
Ryan Ferguson
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Default

Sydney Hoeltzli wrote:

I think it is well worth reading, especially for those who
seem to feel the tach and the T/C are superfluous.


I read it. I don't really get anything from it which would apply to the
turn coordinator versus AI discussion of late. The author uses some
terminology rather loosely - referring to pressure instruments and
including in the list (I think?) the DG and AI. It's not clear to me
how or why he lost his vacuum driven gyros from the story as posted. I
also think he might have derived some erroneous conclusions from his
close encounter - for example he referred to engine noise as the 'best
guide to inversion.' Sure, engine noise can be helpful for determining
whether the airplane is in a dive or climb, but it might be doing either
while inverted and the pilot may not know.

(What an amazing coincidence that he appeared to have been hit by an R/C
airplane - in a cloud! Pretty unbelievable.)

Like others in the aforementioned thread, I take attitude information
pretty seriously. I fly two vacuum pumps and two AIs. Both AIs are
air-driven. My system vulnerability is my plumbing, which I accept as a
reasonable risk.

My secondary AI lives on the right side of the panel. Now, admittedly I
fly my airplane a lot, and from both seats, and practice partial panel
fairly regularly. (My idea of fun is plowing around partial panel, OEI,
in a single-receiver VOR intersection hold.) As such, I just don't get
the hubbub about the location of the damn thing. If it's on the right
side of the panel and you need to look to the right to see it, then do
so. If you're sitting in the right seat and need to look to the pilot's
side of the panel for information, then do that. If one's scan is so
weak that one can't handle looking across the panel for attitude
indication, one should practice their partial panel skills more often.
If one is more susceptible to spatial disorientation from looking at a
wider swatch of panel real estate, one needs to fly with an instructor
or safety pilot until they're able to handle it. I regard these things
as basic requirements to fly instruments.

In line with this thinking, my personal feeling is that the location of
the indicator may not be the culprit. The problem more likely is the
ability to modify one's actions to properly react in an emergency such
as vacuum or attitude indicator failure in IMC. (And yes, I will always
call that an emergency, regardless of how comfortable one may be flying
partial panel.) I think people that lose their cool in recoverable
emergencies will tend to break airplanes regardless of how their
instrument panel was laid out.

One other side note. You mentioned that the tach should be located
where it can be part of the primary scan. In the Twin Comanche, almost
all of the ships flying have MAP and RPM on the copilot side of the
panel. That area of the panel simply has to be part of your scan if you
wish to include those instruments. Personally, I think this is a good
thing, because it tends to force the pilot to use the whole panel rather
than fixating on the six-pack.

Best,

Ryan
CFI-ASE-AME, CFI-RH, CP-ASMEL-IA, CP-RH, AGI

  #3  
Old July 15th 03, 04:41 AM
Sydney Hoeltzli
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Default

Ryan Ferguson wrote:
Sydney Hoeltzli wrote:
I think it is well worth reading, especially for those who
seem to feel the tach and the T/C are superfluous.


I read it. I don't really get anything from it which would apply to the
turn coordinator versus AI discussion of late.


Oh, well.

The author uses some
terminology rather loosely - referring to pressure instruments and
including in the list (I think?) the DG and AI.


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.

It's not clear to me
how or why he lost his vacuum driven gyros from the story as posted.


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

I
also think he might have derived some erroneous conclusions from his
close encounter - for example he referred to engine noise as the 'best
guide to inversion.' Sure, engine noise can be helpful for determining
whether the airplane is in a dive or climb, but it might be doing either
while inverted and the pilot may not know.


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)

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?

Like others in the aforementioned thread, I take attitude information
pretty seriously. I fly two vacuum pumps and two AIs. Both AIs are
air-driven. My system vulnerability is my plumbing, which I accept as a
reasonable risk.


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?

If one is more susceptible to spatial disorientation from looking at a
wider swatch of panel real estate, one needs to fly with an instructor
or safety pilot until they're able to handle it. I regard these things
as basic requirements to fly instruments.


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?

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

In line with this thinking, my personal feeling is that the location of
the indicator may not be the culprit. The problem more likely is the
ability to modify one's actions to properly react in an emergency such
as vacuum or attitude indicator failure in IMC. (And yes, I will always
call that an emergency, regardless of how comfortable one may be flying
partial panel.)


Can't argue here. Anything which bites so many pilots who "ought to
be able to handle it" for reasons which are unclear at present,
deserves to be handled like a live viper IMHO. Carefully, and with
all available precautions.

I think people that lose their cool in recoverable
emergencies will tend to break airplanes regardless of how their
instrument panel was laid out.


Can't argue with that, either. OTOH, I do think that it's too
simple to dismiss some of the problems supposedly good, experienced
pilots have as entirely due to lack of proficiency, unless one has
solid evidence that this is the case.

One other side note. You mentioned that the tach should be located
where it can be part of the primary scan.


Um, not exactly. I say one should consider this experience when
deciding whether one wishes to relocate the tach outside one's
primary scan.

In the Twin Comanche, almost
all of the ships flying have MAP and RPM on the copilot side of the
panel.


If you'll pardon my pointing this out, I do think a plane with an
adjustable pitch prop has different issues for power management.
I notice this when I let pilots who are used to same take the
controls of my plane.

Cheers,
Sydney

  #4  
Old July 15th 03, 09:28 AM
Dylan Smith
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Default

On Tue, 15 Jul 2003 03:41:55 GMT, Sydney Hoeltzli wrote:
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)


If you have long enough to do that test whilst inverted in an AA5,
within a couple of seconds, you'll be greeted by silence. I don't know
about the AA5, but the C140 would quit if you did a zero-g pushover
slightly too vigorously!

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

  #5  
Old July 15th 03, 02:00 PM
Ryan Ferguson
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Posts: n/a
Default

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)


 




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