Compass trouble

(Drew Dalgleish) writes:

A GPS knows where it is, not which way it is facing.

Do it while flying. The GPS know which way it's going.

Only by inference.
--
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is busy, hung or dead....................................20915-1433

On Thu, 17 Apr 2008 02:03:18 GMT, (Drew
Dalgleish) wrote:

On Wed, 16 Apr 2008 05:19:27 +0000 (UTC),
(Alan) wrote:

In article (Drew Dalgleish) writes:

My home airport has a compass rose and I use that. Taxiing aroud and
getting lined up on each heading takes me quite a bit longer than
that. Having a helper would speed things I'm sure but if we consider
man hours since the OP was about mechanics time then double your
15minutes.

It is easier to shut down and just turn the plane from heading to
heading manually.

I was going to ask how do you know if it's an accurate land
compass but it occurs to me that a GPS would do the job and then you
could do it by yourself .

How?

A GPS knows where it is, not which way it is facing.


Alan
Do it while flying. The GPS know which way it's going.

You really don't seem to understand -- heading and track are two
different things. They are only aligned if you are flying directly
into, or away from, the wind.

So your GPS is pretty well useless in flight for aligning a compass,
as you can never tell precisely the wind direction aloft. Certainly
not within the +/- 3 degrees that you should be trying to calibrate
against.
--
Jay (remove dashes for legal email address)

On Apr 17, 9:15*am, Jay Somerset wrote:
On Thu, 17 Apr 2008 02:03:18 GMT, (Drew





Dalgleish) wrote:
On Wed, 16 Apr 2008 05:19:27 +0000 (UTC),
(Alan) wrote:

In article (Drew Dalgleish) writes:

My home airport has a compass rose and I use that. Taxiing aroud and
getting lined up on each heading takes me quite a bit longer than
that. Having a helper would speed things I'm sure but if we consider
man hours since the OP was about mechanics time then double your
15minutes.

*It is easier to shut down and just turn the plane from heading to
heading manually.

I was going to ask how do you know if it's an accurate land
compass but it occurs to me that a GPS would do the job and then you
could do it by yourself .

*How?

*A GPS knows where it is, not which way it is facing.

* * * *Alan
Do it while flying. The GPS know which way it's going.

You really don't seem to understand -- heading and track are two
different things. *They are only aligned if you are flying directly
into, or away from, the wind.

So your GPS is pretty well useless in flight for aligning a compass,
as you can never tell precisely the wind direction aloft. *Certainly
not within the +/- 3 degrees that you should be trying to calibrate
against.
--
Jay (remove dashes for legal email address)- Hide quoted text -

- Show quoted text -

Someone explained it pretty clearly earlier... use the GPS on the
ground. Taxi slowly to get your heading/track where you want it then
stop slowly and smoothly.

Steve
KDMW

Several years ago we had a Piper at our facility (TGH Aviation/The Gyro House) with the exact same problem. After trying all of the standard procedures to no avail, out of frustration I took a very strong magnet and moved it swiftly up and down the center windshield support strut and then quickly pulled it away. Effectively scrambling (degaussing)the electrons in the metal strut. Much to my surprise, as this was an act of desperation on my part, the compass returned to normal working order and has not had a problem since. This is the only aircraft type where I have ever witnessed this happening. It's a long shot but you might want to try it.

Rich Anderson
President, TGH Aviation

Originally Posted by Road Dog

I took my Piper Warrior in for its annual and the mechanic
said that the compass card was missing and that he'd have
to swing the plane to generate a new one.

After swinging it, he claimed that he couldn't get the
E-W deviation within the minimum. So he suggested we
try "mu" shield (or something) to block the source of
magnetism which he claims is coming from one of the
instruments. (He says the compass works fine outside
the plane.)

Note: The instruments are all original, stock. Nothing
has been changed (except a radio was added which he says
is not the source.)

The mu shield fails too. He says the next thing to try is
to move the compass up to between the visors.

He says he has spent 3 hours on this so far. I'm beginning to
wonder, shouldn't a mechanic be able calibrate a compass
in a stock Piper after 3 hours ? Is he incompetent ?
Padding the bill ? Or does this really take this long ?

He has inspected and fixed everything else. Do you think
its reasonable at this time to ask him to sign off
everything else, and take the plane somewhere else where,
presumably, they know how to calibrate a compass ?

On Thu, 17 Apr 2008 09:46:24 -0700 (PDT), Steve - KDMW
wrote:

On Apr 17, 9:15*am, Jay Somerset wrote:
On Thu, 17 Apr 2008 02:03:18 GMT, (Drew





Dalgleish) wrote:
On Wed, 16 Apr 2008 05:19:27 +0000 (UTC),
(Alan) wrote:

In article (Drew Dalgleish) writes:

My home airport has a compass rose and I use that. Taxiing aroud and
getting lined up on each heading takes me quite a bit longer than
that. Having a helper would speed things I'm sure but if we consider
man hours since the OP was about mechanics time then double your
15minutes.

*It is easier to shut down and just turn the plane from heading to
heading manually.

I was going to ask how do you know if it's an accurate land
compass but it occurs to me that a GPS would do the job and then you
could do it by yourself .

*How?

*A GPS knows where it is, not which way it is facing.

* * * *Alan
Do it while flying. The GPS know which way it's going.

You really don't seem to understand -- heading and track are two
different things. *They are only aligned if you are flying directly
into, or away from, the wind.

So your GPS is pretty well useless in flight for aligning a compass,
as you can never tell precisely the wind direction aloft. *Certainly
not within the +/- 3 degrees that you should be trying to calibrate
against.
--
Jay (remove dashes for legal email address)- Hide quoted text -

- Show quoted text -

Someone explained it pretty clearly earlier... use the GPS on the
ground. Taxi slowly to get your heading/track where you want it then
stop slowly and smoothly.

Yes, if you have a large enough ground area to do that at the 6
different directions (back and forth) that you need. Most GA airports
do not have anything like that amount of space. You would have to taxi
for at least 50-100 yards to have a reliable track.

But yes, in theory, this would work.
--
Jay (remove dashes for legal email address)

Do you really have to quote a hundred lines of previous text for a four line
answer?

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford



"Jay Somerset" wrote in message
...

Yes, if you have a large enough ground area to do that at the 6
different directions (back and forth) that you need. Most GA airports
do not have anything like that amount of space. You would have to taxi
for at least 50-100 yards to have a reliable track.

"Jay Somerset"
You would have to taxi
for at least 50-100 yards to have a reliable track.

But yes, in theory, this would work.
--
Jay

No. 10 or 20 feet will be just fine.

On Fri, 18 Apr 2008 09:51:13 -0700, "karl mcgruber" skywagon
wrote:



"Jay Somerset"
You would have to taxi
for at least 50-100 yards to have a reliable track.

But yes, in theory, this would work.
--
Jay

No. 10 or 20 feet will be just fine.

No it won't. Watch a stationary GPS give you a position that wobbles
up to 20-50 feet away from its centroid. If you use a very short
track, you could be out way more than the allowable compass deviation.

Simple geometry -- work out the angular error with just a 10 foot
lateral error from a 20 foot base. (Hint: 30 degrees)
--
Jay (remove dashes for legal email address)

On Fri, 18 Apr 2008 06:48:40 -0700, "RST Engineering"
wrote:

Do you really have to quote a hundred lines of previous text for a four line
answer?

Jim

Gee. Guess that's what happens when one tries to keep the enough
context in a thread so that someone who comes into the discussion
without having seen all the earlier posts can understand the issues.

But it was only 48 lines -- why exaggerate?
--
Jay (remove dashes for legal email address)

On 2008-04-19, Jay Somerset wrote:
On Fri, 18 Apr 2008 06:48:40 -0700, "RST Engineering"
wrote:
Do you really have to quote a hundred lines of previous text for a four line
answer?
Gee. Guess that's what happens when one tries to keep the enough
context in a thread so that someone who comes into the discussion
without having seen all the earlier posts can understand the issues.

Usenet etiquette has, for at least two decades, been to trim away what
you're not commenting on, keeping just enough text to make your answer
comprehensible.

There are folks around here who refuse to trim at all. I use a 43-line
terminal window to read Usenet with, and when it's full of stuff quoted 7
layers deep, I just hit N and go to the next message.

Posting like that just gives ammunition to those who argue that people
should adopt the equally abhorrent practice of top-posting.

If someone wants context, they can use the "read parent article" function of
their newsreader.
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (FRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC (ordered 17 March, delivery 2 June)