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Backup gyros - which do you trust?



 
 
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  #1  
Old July 13th 03, 01:35 PM
Dan Luke
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Default Backup gyros - which do you trust?

"Steve House" wrote:
I've been reading with interest the several threads where a number of

people
have strongly pointed out the advantages of a backup electric AI to

supplant
a vacum driven main AI. But I'm reminded of the saying "A man with a good
watch always knows what time it is. A man with two watches is never

sure."

This is a very interesting issue, to me. Reading the records of IMC
loss-of-control accidents is very unsettling to this single pilot IFR flyer
because of the cases where there *was* backup attitude instrumentation
available. Even when there wasn't, the pilots usually had at least the turn
coordinator to help keep the aircraft upright. It is too simple to chalk up
all these accidents simply to lack of proficiency. There is something else
going on - some human factors issue that has not been properly identified. I
suspect it may be related to task saturation. If so, instrument panel
clutter could be a contributing factor.

So I'm toodling along in IMC with no outside horizon reference and I see

my
two AIs don't agree with each other. How do I determine which to trust?

If
I had a third, I could go with a 2 of 3 voting strategy of course, but

with
only two, what do you do to decide which is operating properly and which

one
has faulted? Obviously I can look for consistency with other

instruments -
does my DG or Turn indicator show I'm turning, does the VSI show a climb

or
descent - but what would be the best strategy given the various ways

vacuum
or electric driven instruments can fail?


My strategy is to include a yoke-mounted GPS displaying a synthetic HSI in
my scan. This works wonderfully well in training, but I am not sure how well
I would do in a real situation where my AI suffered a gradual failure.
--
Dan
C172RG at BFM


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  #2  
Old July 13th 03, 04:06 PM
Sydney Hoeltzli
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Dan Luke wrote:

This is a very interesting issue, to me. Reading the records of IMC
loss-of-control accidents is very unsettling to this single pilot IFR flyer
because of the cases where there *was* backup attitude instrumentation
available. Even when there wasn't, the pilots usually had at least the turn
coordinator to help keep the aircraft upright. It is too simple to chalk up
all these accidents simply to lack of proficiency. There is something else
going on - some human factors issue that has not been properly identified.


Concur. I, too, don't think it's entirely lack of proficiency. I think
there are pilots who have training and proficiency, who, in the words
of my CFI, "ought to be able to do it", who don't. And clearly backup
AI is no panacea.

Obviously I can look for consistency with other instruments -
does my DG or Turn indicator show I'm turning, does the VSI show a climb
or descent - but what would be the best strategy given the various ways
vacuum or electric driven instruments can fail?


Having an inventive CFI who has little habits like mind-f***ing
me into doubting my AI while palming the TC fuse, I think the best
strategy is delimited above. *Instrument cross check is essential*

Rod Machado's "Instrument Pilot Survival Manual" delineates something I
haven't seen elsewhe

Turn triangle of agreement: AI, TC, compass
Pitch triangle of agreement: AI, VSI, alt static on/off

The point is to deliberately cross-check instruments
which depend upon independent power sources.

The problem (for me anyway) in training is that my compass is
mounted on the windshield bow and it's impossible to keep it
in my scan in VMC under the hood w/out extensive "cheating".

I also think Machado's under-utilizes ASI and hearing. I
think the reasoning is that there are three sources of ASI
failure and only two for VSI, one of which alt static
eliminates. But when forced to fly instruments without static
instruments, I found hearing was a fairly precise means of
pitch control (at constant power for a fixed-pitch prop)

Interested to see what others say: this topic should elicit a
lot of opinions.

Cheers,
Sydney



  #3  
Old July 13th 03, 05:20 PM
Big John
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Dan and others

Full panel makes it easier for a qualified pilot to fly IFR. I doubt
a properly trained pilot is over whelmed by task saturation. There may
be lots of guages in the cockpit but only a few are included in your
primary scan on IFR.

How many pilots today practice partial panel and can fly it when
required? Not many I'd say. Never hear it discussed in any avation
groups any more as failure rate of gyro's is very small..

With single or dual gyro flight instrumnts and the problem of knowing
which one to believe all you have to do is check your partial panel
instruments to identify the correct gyro.

All of this takes understanding of IFR flying and partital panel
practice anticipating a gyro failure. Instrument (gyro) failures are
emergencies that can kill you if not proficient on partial panel.

How many GA pilots today could make even a NDB approach partial panel
much less a ILS or GPS approach?

Many areas of flyng have high risk. One can only try to stay ahead of
the airplane (and system) to reduce risk.

Fly safe and a nice day to all.

Big John



On Sun, 13 Jul 2003 07:35:24 -0500, "Dan Luke"
wrote:

"Steve House" wrote:
I've been reading with interest the several threads where a number of

people
have strongly pointed out the advantages of a backup electric AI to

supplant
a vacum driven main AI. But I'm reminded of the saying "A man with a good
watch always knows what time it is. A man with two watches is never

sure."

This is a very interesting issue, to me. Reading the records of IMC
loss-of-control accidents is very unsettling to this single pilot IFR flyer
because of the cases where there *was* backup attitude instrumentation
available. Even when there wasn't, the pilots usually had at least the turn
coordinator to help keep the aircraft upright. It is too simple to chalk up
all these accidents simply to lack of proficiency. There is something else
going on - some human factors issue that has not been properly identified. I
suspect it may be related to task saturation. If so, instrument panel
clutter could be a contributing factor.

So I'm toodling along in IMC with no outside horizon reference and I see

my
two AIs don't agree with each other. How do I determine which to trust?

If
I had a third, I could go with a 2 of 3 voting strategy of course, but

with
only two, what do you do to decide which is operating properly and which

one
has faulted? Obviously I can look for consistency with other

instruments -
does my DG or Turn indicator show I'm turning, does the VSI show a climb

or
descent - but what would be the best strategy given the various ways

vacuum
or electric driven instruments can fail?


My strategy is to include a yoke-mounted GPS displaying a synthetic HSI in
my scan. This works wonderfully well in training, but I am not sure how well
I would do in a real situation where my AI suffered a gradual failure.


  #4  
Old July 13th 03, 07:38 PM
James Robinson
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Dan Luke wrote:

It is too simple to chalk up all these accidents simply to lack of
proficiency.


I was just reading the NTSB report of the King Air that crashed in
Colorado, attributed to spatial disorientation after a partial panel
failure. It seems representative of the problem. The facts are
chilling:

- IMC, alt. 23,200 ft.
- Two person cockpit.
- Experienced pilot - 5117 hours total, 2520 in type.
- Partial panel loss due to AC power failure.
- Failure immediately indicated by flags on affected instruments.
- Remaining instruments, powered by vacuum:
Left - airspeed, turn/slip,
Right - airspeed, turn/slip, altimeter, attitude.
- Aircraft began gently increasing turn within one minute of failure.
- Time between instrument loss and impact - one minute, 33 seconds
- Flight path consistent with graveyard spiral

http://www.ntsb.gov/publictn/2003/AAR0301.pdf

There is something else going on - some human factors issue that
has not been properly identified. I suspect it may be related to
task saturation. If so, instrument panel clutter could be a
contributing factor.


One comment in the report was that the pilot might have had a tendency
to focus on a single problem, and mot paid attention to other things.
He could have been trying to troubleshoot the electrical problem, and
not handed control over to the copilot, who would have had a better view
of the remaining functional instruments.

In any event, it is amazing how quickly the pilot lost control of the
aircraft, considering how this should have been fairly routine: If an AC
inverter had failed, then the changeover to the remaining inverter is
accomplished with a simple flip of a switch, and should have been almost
a reflexive action. The failure would have been immediately obvious, so
it wasn't one of those insidious failures that people don't notice at
first. An experienced IFR pilot should have been aware of the need to
maintain attitude and yet lost control almost immediately. In reading
the report, it seems like such an avoidable accident, yet...
  #5  
Old July 14th 03, 02:31 AM
Sydney Hoeltzli
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Default

Big John wrote:

How many pilots today practice partial panel and can fly it when
required?


Dunno. We sure do.

Never hear it discussed in any avation
groups any more as failure rate of gyro's is very small..


Couldn't prove the latter by me (2 per 1000 hrs). Then there's
the dry vacuum pump (1 per 1000 hrs). Not meaningful as statistics
of course.

How many GA pilots today could make even a NDB approach partial panel
much less a ILS or GPS approach?


I'm confused here -- the implication seems to be that you feel
an NDB approach would be easier partial-panel than an ILS or
GPS approach. If I'm interpreting you correctly, why?

Thanks,
Sydney

  #6  
Old July 14th 03, 02:34 AM
Sydney Hoeltzli
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Default

James Robinson wrote:

One comment in the report was that the pilot might have had a tendency
to focus on a single problem, and mot paid attention to other things.
He could have been trying to troubleshoot the electrical problem, and
not handed control over to the copilot, who would have had a better view
of the remaining functional instruments.


This is poor CRM if it is the case.

Did the report say anything about the training of the pilots? I
woulda thought they did regular sim stuff, where I assume the
instructors put you through the wringer on various failues.

The failure would have been immediately obvious, so
it wasn't one of those insidious failures that people don't notice at
first. An experienced IFR pilot should have been aware of the need to
maintain attitude and yet lost control almost immediately. In reading
the report, it seems like such an avoidable accident, yet...


Yeah, that's what gets me about so many of these.

Sydney

  #7  
Old July 14th 03, 05:02 AM
Sydney Hoeltzli
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Julian Scarfe wrote:

http://www.dft.gov.uk/stellent/group...cst?n=5232&l=4

tells a similarly chilling story of a Bandeirante that lost one of its two
AIs resulting in a loss of control.


What do you think of the conclusions? They seem to be:
1) prevent AIs from failing
2) since 2 AIs weren't enough to keep the plane upright (combined
with 2 turn and banks, 2 of every other instrument), require
passenger planes to have 3

(agree, chilling)
Sydney

  #8  
Old July 14th 03, 05:09 AM
Big John
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Sidney

NDB approach is a non precision approach. Takes less Partial Panel
proficiency.

ILS is a precision approach.

GPS could be either a precession or non precision approach depending
on configuration. Eventually all will be precession.

You can flop around on a NDB approach with it's higher minimums easier
on partial panel than you can on a precision ILS.

On instruments, it is hard enough with full panel to fly precision IFR
especially if the ILS beams have splits in them and the needles bounce
from stop to stop at minimums. We used to practice at Scramento and
never felt comfortable making the ILS approach there due to erratic
needle movements on final.

Does that explain my feelings enough?

It's been so many years since I made a real partial panel approach.
It was a Radio Range (A/N) approach as I recall. Hit cone of silence,
turned to heading to field, let down to minimum altitude and flew the
time (minutes and seconds) to field. All the pilots wore those fancy
chronometers to time from cone of silence to field for instrument
approaches in those days )

Some still wear along with the white scarf )

People laughed at the white scarf but in a fighter when it was hot you
could rub the skin off your neck looking for enemy aircraft. The soft
(silk) white scarf made it easier to keep your head on a swivel like
they told you. First time you were jumped and didn't see them coming
they didn't have to tell you again to keep a look out behind you if
you survived that first combat mission )

Good flying Sydney

Big John

If you are seriously going to fly IFR than all of your landings should
be from practice instrument approaches. This is what we did in the Air
Defense Command. One out of a hundred would be a straight VFR landing.
When Wx was bad we were right at home since we had been flying the
approach each flight each day. Even if you don't use a hood, the
procedures and communications become a piece of cake.


----clip----

How many GA pilots today could make even a NDB approach partial panel
much less a ILS or GPS approach?

I'm confused here -- the implication seems to be that you feel
an NDB approach would be easier partial-panel than an ILS or
GPS approach. If I'm interpreting you correctly, why?

Thanks,
Sydney

  #9  
Old July 14th 03, 06:10 AM
Sydney Hoeltzli
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Big John wrote:

NDB approach is a non precision approach. Takes less Partial Panel
proficiency.


I'm quite aware of what is and isn't a precision approach.

What I don't understand is why you feel it's easier to fly an
NDB approach than an ILS approach partial-panel.

It seems to me that the NDB approach most strongly requires
accurate heading information. The course to be flown can not
be determined from the position of the ADF needle alone, it
can only be determined by comparing the ADF bearing to heading.
If your only source of heading info is a compass dancing wildly
as you bounce around, this gets "too interesting"

On an ILS or GPS approach, OTOH, it seems to me that the
course to be flown can be determined from the CDI position
alone. Needle left, turn left etc.

You can flop around on a NDB approach with it's higher minimums easier
on partial panel than you can on a precision ILS.


I don't understand this at all. Yes, the ILS becomes increasingly
sensitive as one descends closer to DH. But, if the wx is such
that the 800 ft minimums (or 600, or whatever they are) on an
NDB approach will get one in, one need not fly the ILS minimums
but can "flop around" on the less sensitive portion.

OTOH, if the wx is really crappy, all the flopping around on an
NDB you might care to do won't help you.

On instruments, it is hard enough with full panel to fly precision IFR
especially if the ILS beams have splits in them and the needles bounce
from stop to stop at minimums. We used to practice at Scramento and
never felt comfortable making the ILS approach there due to erratic
needle movements on final.


I've never experienced anything like this. Is this a Cat II or III
ILS?

Does that explain my feelings enough?


Not really I'm afraid. I must say the view that partial panel
NDB approachs are the most difficult seems to be held by many
of the local DEs, who will require a partial-panel NDB if there
is an ADF installed in the plane.

It's been so many years since I made a real partial panel approach.
It was a Radio Range (A/N) approach as I recall. Hit cone of silence,
turned to heading to field, let down to minimum altitude and flew the
time (minutes and seconds) to field. All the pilots wore those fancy
chronometers to time from cone of silence to field for instrument
approaches in those days )


Whew...is this the sort of approach being described in "Fate is
the Hunter"? How would you handle adjusting groundspeed vs. time?
Would you guesstimate your groundspeed from time between waypoints
before initiating descent, would someone on the ground give you
winds from which you'd calculate groundspeed? Would you adjust
power to always fly the same groundspeed, or adjust time? Sorry
for all the naive questions, but pilots who actually flew radio
range approaches are few and far between.

These days, if I time an approach where I could use DME to define
the MAP my instructor beats me with a board "timing is the least
accurate way to determine the MAP! Never depend upon time if
there's another way!" And he's not a young whippersnapper
either.

Appreciate your comment re practice instrument approaches.

Cheers,
Sydney

  #10  
Old July 14th 03, 09:08 AM
Big John
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Sidney

On Mon, 14 Jul 2003 05:10:26 GMT, Sydney Hoeltzli
wrote:

Big John wrote:

NDB approach is a non precision approach. Takes less Partial Panel
proficiency.


I'm quite aware of what is and isn't a precision approach.

You ask and I gave a straight forward answer. Why did you parse my
answer and get snippy???? If you didn't want to know, why ask?

Are you trying to tell me it's not easier to fly a PP NDB approach
than a PP ILS?

What I don't understand is why you feel it's easier to fly an
NDB approach than an ILS approach partial-panel.


How many times have you flown a hard IFR partial panel NDB or ILS
approach? Are you making your statements from reading a book or from
bar talk? If you don't want to take advice from someone who has been
there and done that then use your own procedure. There are many ways
to fly an airplane, some better and more safe than others but only the
individual can make the decision of what is right for him/her within
the rules and their experience level.

It's too bad we are not closer and I could jump in and let you
demonstrate to me how easy it is to fly PP without killing us.

It seems to me that the NDB approach most strongly requires
accurate heading information. The course to be flown can not
be determined from the position of the ADF needle alone, it
can only be determined by comparing the ADF bearing to heading.
If your only source of heading info is a compass dancing wildly
as you bounce around, this gets "too interesting"

A NDB can be flown with very sloppy heading control. Use whisky
compass outbound in pattern and just point the needle at 360 degrees
(top of dial) in bound. After needle swing you can use time and
distance and compass heading to field letting down to minimums.

On an ILS or GPS approach, OTOH, it seems to me that the
course to be flown can be determined from the CDI position
alone. Needle left, turn left etc.


I'd like to see you PP trying to use GPS to make an approach. It's
hard enough to keep the airplane flying PP without using the benefits
of GPS. Not saying it can not be done but I'd bet against anyone doing
it successfully and win a bundle. Could throw an Irish Wake with
dancing and drink galore.

Another post pointed out an individual practicing using his back up AI
across the panel and got vertigo. He probably was moving his head back
and forth which gives you vertigo when on instruments, Your scan is
only with your eye balls or you will probably get vertigo.

You can flop around on a NDB approach with it's higher minimums easier
on partial panel than you can on a precision ILS.


I don't understand this at all. Yes, the ILS becomes increasingly
sensitive as one descends closer to DH. But, if the wx is such
that the 800 ft minimums (or 600, or whatever they are) on an
NDB approach will get one in, one need not fly the ILS minimums
but can "flop around" on the less sensitive portion.


True. If you have NDB minimums and only an ILS then you can probably
get down using the ILS assuming you are proficient enough to fly the
two needles and all the PP instruments required to just keep the bird
airborne.

OTOH, if the wx is really crappy, all the flopping around on an
NDB you might care to do won't help you.

Again. Want to see you make a IFR PP ILS. Doubt if I could when I was
able to fly the box the bird came in. It's very hard and very
dangerous.

On instruments, it is hard enough with full panel to fly precision IFR
especially if the ILS beams have splits in them and the needles bounce
from stop to stop at minimums. We used to practice at Scramento and
never felt comfortable making the ILS approach there due to erratic
needle movements on final.


I've never experienced anything like this. Is this a Cat II or III
ILS?

Don't know. It was the initial type that was used for years. Each one
had different beams causing different display in cockpit from the
installation at each field. Some fields were so bad that they could
not install an ILS and meet FAA standards. That was one of the reasons
(to learn the ILS quirks) an Airline Pilot had to make several flights
into an airport before he was checked out to fly as captain to that
field.

Does that explain my feelings enough?


Not really I'm afraid. I must say the view that partial panel
NDB approachs are the most difficult seems to be held by many
of the local DEs, who will require a partial-panel NDB if there
is an ADF installed in the plane.


Don't know where you are reading this in my posts. A PP ADF is the
easiest PP approach to fly IFR. Still not easy, but the easiest.

It's been so many years since I made a real partial panel approach.
It was a Radio Range (A/N) approach as I recall. Hit cone of silence,
turned to heading to field, let down to minimum altitude and flew the
time (minutes and seconds) to field. All the pilots wore those fancy
chronometers to time from cone of silence to field for instrument
approaches in those days )


Whew...is this the sort of approach being described in "Fate is
the Hunter"? How would you handle adjusting groundspeed vs. time?
Would you guesstimate your groundspeed from time between waypoints
before initiating descent, would someone on the ground give you
winds from which you'd calculate groundspeed? Would you adjust
power to always fly the same groundspeed, or adjust time? Sorry
for all the naive questions, but pilots who actually flew radio
range approaches are few and far between.

Sidney. All of the above G The approach plate gave the time to field
in minutes and seconds listing several speeds to accommodate all the
aircraft in inventory. Normally max time would only be 3-4 minutes and
normally just 1-2 minutes after crossing cone of silence. You rarely
landed straight in and many of the headings to field were not lined up
with a runway. After sighting the field you would circle and land on
the active runway. If you were in radio contact with the field/tower
you could get surface wind and compute a ground speed from cone of
silence to field, other wise you made a WAG from forecast and what you
encountered en route. As you only were flying a couple of minutes and
the wind would only make the difference of a few seconds to field it
was not a super big problem in most cases.. Remember a ceiling of
6-800 feet (above obstructions) was the norm in those days. None of
the 200 & 1 (or less) like today.. Hope this gives you a feel for how
crude things were in those days. Norm was when WX was bad we sat until
it improved and then continued cross country. As an aside, in all my
years of flying, I only made one zero zero landing.

These days, if I time an approach where I could use DME to define
the MAP my instructor beats me with a board "timing is the least
accurate way to determine the MAP! Never depend upon time if
there's another way!" And he's not a young whippersnapper
either.


If all the instruments and nav aids are working then he is correct but
when the bottom falls out then timing is a very good fall back. Tape
the DME for him and fly time and then uncover the DME and see how far
you are off. If done properly is pretty accurate for short distances.
Doing on occasion gives you confidence in timing, if required.

Appreciate your comment re practice instrument approaches.


I instructed for so many years in heavy iron I tend to push the
routines I developed to give maximum safety and yet perform the
mission. As I've said, there may be other ways to fly but what I push
has stood the test of time and is a good place to start until one gets
lots of experience.

As I have also said prior, these postings have taken the place of what
we called hanger flying in the old days where lots of tips and tricks
were passed on to the younger pilots by the old gray beards.

For example, I can loop a T-6 starting at zero indicated airspeed. Two
people and normal load of fuel. No tricks, just super technique.

Can also do a double immelman (sp) in a T-33. Only a couple of us I
know who did that. Max use of energy. One good friend of mine who did,
died a few years ago (probably drank himself to death). At reunion in
San Antonio we stayed in the hotel room and knocked off a couple of
quarts of vodka to get ready for evenings activities while the gals
went 'out' to do what women do G. He was the one that was shot down
in Europe and stole a FW-190 and flew it back to England. Got gear up
but didn't know how to unlock and get the gear down so had to belly in
G His exploit has been published a few times in the War Stories
magazines.

Enough rambling.

I'm going to back out of most of these threads and let yu'all have at
it. I'll just read and enjoy. Might even look at a sport bird since I
can't get a third class anymore. At least with out several years and a
lot of time and money to fight the system. Have you heard of any one
getting by OK City with a pacemaker? I pass a monthly check ok.

Have enjoyed many of your posts. Keep it up. You are not afraid to ask
questions which is good.

Erin go bragh

Big John

Best instruments you can buy and also radio's. Practice instruments
and fly at least 10 hours a month (100 hours a year minimum).

Air Force ran an expensive study that showed 17 hours a month gave
minimum accident rate in heavy iron. Less than 17 hours, proficiency
suffered. More than 17 hours you were exposed to flying hazards more
and more accidents. The 17 hours a month is close to 200 hours a year
which is a very good figure if you have the money and time to fly that
much.
 




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