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Backup gyros - which do you trust?



 
 
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  #11  
Old July 14th 03, 02:25 AM
Roy Smith
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Ray Andraka wrote:
Personally, I think the instrument scan typically taught relies too
heavily on the AI given its relatively low reliability.
Unfortunately, the alternative is a scan that works a bit more like a
partial panel scan using the AI as supporting, not primary. Such a
scan is much harder to master and requires considerable finesse to
keep from chasing the needles. It is not one I would expect to be
able to teach someone just learning to fly by instruments.


You are probably right. When I did my initial IFR training, my
instructor was very big on partial panel work. As a result, I learned
to not rely on the AI, and I find partial panel approaches (in training,
anyway) almost a non-event.

The downside, is that I suspect I don't use the information the AI gives
me as much as I should. I tend to fly pitch by airspeed, not by the AI.
This probably makes me not as smooth and precise as I might otherwise
be. But I do have a lot of confidence that I can fly an approach on the
TC and ASI alone.
  #12  
Old July 14th 03, 02:39 AM
David Megginson
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Roy Smith writes:

The downside, is that I suspect I don't use the information the AI gives
me as much as I should. I tend to fly pitch by airspeed, not by the
AI.


Are you sure that using the ASI for pitch doesn't make you smoother?
I think that a couple of knots difference is more noticeable than a
fraction of a degree change in the AI pitch indication.

My problem is that managing pitch with the ASI gets hard in turbulence.


All the best,


David

--
David Megginson, , http://www.megginson.com/
  #13  
Old July 14th 03, 02:48 AM
Sydney Hoeltzli
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C J Campbell wrote:
Newer vacuum AIs have warning flags, dual vacuum pumps, and vacuum warning
lights on the annunciator panel. If I had an electric AI and a vacuum AI and
they disagreed markedly, I would be suspicious of the one having warning
lights and flags all over it.


CJ,

How do newer vacuum AIs come with dual vacuum pumps?

We have a "warning flag" on our newer AI. I note that it is really
a low vacuum flag. It doesn't say a thing about how reliably the
instrument itself is operating.

Sydney

  #14  
Old July 14th 03, 02:57 AM
Sydney Hoeltzli
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Ray Andraka wrote:
There are several things you can add to help with the identification, In my
plane I have a low vacuum warning light (part of the precise flight backup)
mounted between the AI and DG. The AI is one of the sigmatec ones with a vacuum
flag, so that if vacuum is lost in the instrument but not in the system I still
know about it right away. These warnings cover identification of the more
common cause of loss of the AI. The other failure mode would be failure of the
gyro, in which case I don't believe you get the insidious gradual spin-down like
you do with loss of vacuum.


Ray,

I'll speak to the latter.

A failing horizon gyro may not "spin down". But it can still
be insidious. Example: our AI had a period where, in level flight,
it would jump up and indicate a rather nose-high attitude. Fail
to catch it and you'd be in a rather steep dive. Then it would
go back to normal. Then jump up again....finally it broke and
unmistakably started spinning in a nauseating fashion, but the
"breaking" process could easily have caused a loss of control for
a pilot w/out a good cross-check (our failure happened VMC)

Cheers,
Sydney

  #15  
Old July 14th 03, 03:04 AM
Sydney Hoeltzli
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Richard Kaplan wrote:

Put it where the turn coordinator is located and the put the turn
coordinator off to the side somewhere..


N. F. W.

I think it's time I had a really, really, good hunt for
that post about the Grumman getting flipped upside down
and dumped into IMC after (what was probably) a collision
with an RC plane.

Those Electric and Vacuum AIs come with a get-your-life-back
guarantee they honestly, really truly, won't tumble, never ever,
no matter what, even if I do? How do I test it, in a non-aerobatic
plane not approved for spins?

Cheers,
Sydney

  #16  
Old July 14th 03, 03:11 AM
Newps
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C J Campbell wrote:
Newer vacuum AIs have warning flags, dual vacuum pumps, and vacuum warning
lights on the annunciator panel. If I had an electric AI and a vacuum AI and
they disagreed markedly, I would be suspicious of the one having warning
lights and flags all over it.


I just bought a new AI this spring. For an extra $50 or so you can get
the one with the flag. Since I already have the EI volts/amps
instrument that has warning lights for both high and low voltage, but no
warning light for the vacuum pump, I spent a little extra for the flag.
Now I don't need a suction warning lamp.

  #17  
Old July 14th 03, 03:21 AM
Clay
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Stefan "stefan"@mus. INVALID .ch wrote in message ...
Darrell wrote:

The presence of two attitude indicators is especially valuable when they
disagree. That disagreement will direct your attention to the needle/ball
and basic flight instruments to help determine which one is correct. With a
single AI you could more easily follow a gyro error without noticing a
difference in the other basic instruments until it was too late.


I don't understand this. Needle/ball is always included in my basic
scan. As a starting point on toubleshooting, they are more reliable than
the AI. Am I the only who knows this?

Stefan


Stefan, You have hit the nail on the head. BRAVO!!!!!!!
Many of the real good instrument pilots know that needle, ball,
airspeed are the three essentials to flying. These are the most
reliable instruments on the panel. Once these are mastered then the
rest of the instruments will just make things easy.
Too many of us have forgotten the basics or have just gotten lazy.
When is the last time you flew a true NDB approach? With loran, GPS,
LOC & glide slopes, and vectoring, insturment flying is not that
difficult.
During an ICC, have your instructor give you a real good partial panel
workout.
It is rare to loose a gyro but it happens. Many pilots have lost
their battle with gravity during IMC because they forgot the basics.
This is especially true after loosing a vac pump or electrical system.
Clay
  #18  
Old July 14th 03, 03:35 AM
Richard Kaplan
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"Sydney Hoeltzli" wrote in message
...

Those Electric and Vacuum AIs come with a get-your-life-back
guarantee they honestly, really truly, won't tumble, never ever,
no matter what, even if I do? How do I test it, in a non-aerobatic
plane not approved for spins?


Sure they can tumble. And I would agree they would tumble before the turn
coordinator. But certainly they won't tumble at anything less than 60
degrees bank; the whole idea of the two AIs is to stop the spatial
disorientation profile way before you approach anything like an aerobatic
maneuver.

Also I am not saying you have to put the turn coordinator somewhere where
you will get vertigo... just not necessarily in the immediate 6-pack area,
perhaps instead closer to where most airplanes have their CDIs. It will
still be readable if you somehow get rolled nearly inverted by wake
turbulence. And in the far more likely situation of a vacuum failure, you
will be very glad your electric AI is right up there in your primary scan
area.

--
Richard Kaplan, CFII

www.flyimc.com


  #19  
Old July 14th 03, 03:41 AM
Richard Kaplan
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wrote in message
...


Our Arrow has a backup electric AI on the right side of the panel. It is
turned on whenever I am in or near IMC. I do not include it in my primary
instrument scan, but check it periodically to make sure it is on and

stable.

I think that is a really worrisome location. I just flew last month with a
very experienced instrument student who had a similar arrangement in his
182RG and developed vertigo and nausea while flying partial panel with his
primary AI covered up.. he literally could not manage the plane and asked me
to take over for a while to let him take off the hood and relax.

If you do have the electric AI in that location, it would be helpful for you
to occasionally fly a fairly long cross-country flight with a safety pilot
while you use a hood and cover up the primary AI... that would be helpful to
ensure you are not prone to vertigo from flying with the backup AI alone.


--
Richard Kaplan, CFII

www.flyimc.com


  #20  
Old July 14th 03, 05:37 AM
Big John
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Sidney - just think out of the box

Take AI out of panel leaving hooked up. With power (air/electric)
applied rotate the instrument through all attitudes and see if it
tumbles and where. If it does not meet specs go get your money back.

I fly R/C and doubt if any collision took place. Never heard of it in
AMA magazine and something like that would be a high profile story for
risk of lives and insurance problems.

We don't fly R/C IFR. Only when you can see aircraft to control it. If
it goes in a cloud it crashes and some of the model A/C are worth
several thousands of dollars. Only A/C low over our field are dusters
and they know we are there and we can hear them coming and watch out
for them and stay out of their way. Has worked fine for years.

Big John


On Mon, 14 Jul 2003 02:04:09 GMT, Sydney Hoeltzli
wrote:

Richard Kaplan wrote:

Put it where the turn coordinator is located and the put the turn
coordinator off to the side somewhere..


N. F. W.

I think it's time I had a really, really, good hunt for
that post about the Grumman getting flipped upside down
and dumped into IMC after (what was probably) a collision
with an RC plane.

Those Electric and Vacuum AIs come with a get-your-life-back
guarantee they honestly, really truly, won't tumble, never ever,
no matter what, even if I do? How do I test it, in a non-aerobatic
plane not approved for spins?

Cheers,
Sydney


 




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