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Compass trouble



 
 
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  #1  
Old April 12th 08, 03:45 AM posted to rec.aviation.owning
Road Dog
external usenet poster
 
Posts: 15
Default Compass trouble

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 ?
  #2  
Old April 12th 08, 03:22 PM posted to rec.aviation.owning
Stealth Pilot[_2_]
external usenet poster
 
Posts: 846
Default Compass trouble

On Fri, 11 Apr 2008 19:45:50 -0700, Road Dog
wrote:

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 ?


the problem doesnt seem to be the compass but some stray magnetism in
the aircraft.
swinging a compass takes about 15 minutes.



  #3  
Old April 12th 08, 05:07 PM posted to rec.aviation.owning
Road Dog
external usenet poster
 
Posts: 15
Default Compass trouble

Stealth Pilot wrote:

the problem doesnt seem to be the compass but some stray magnetism in
the aircraft.


So he claims but what would this be that wasn't there
when the plane left the factory ? Without any new
equipment, how could it get so bad that it throws the
compass off more than 10 degrees through mu shield ?

In any case, thanks for the reply.
  #4  
Old April 12th 08, 05:08 PM posted to rec.aviation.owning
[email protected]
external usenet poster
 
Posts: 84
Default Compass trouble

It's possible that something got magnetized during a lightening
strike. Happens
in Mooneys where that 4130 chromealloy tube runs down the center of
the
windshield.

You should check it on cardinal headings with the compensator magnets
completely removed. Should not be off more than about 15 degrees.

I've heard that stronger compensation magnets are available. I think
it would
be better to find the source of interference, as tweeking it that far
will cause
errors on some headings.

BTW, a great way to compensate compasses: On a large part of a ramp,
taxiing
with everything running... Use the track info on the GPS--which is
calibrated in
magnetic heading--to line up on a cardinal heading. Taxi on the
cardinal heading
and smoothly come to a stop without changing the heading -- which can
be
verified by the DG. Much more accurate than lining up on a compass
rose.
Best done with someone along who can make sure you don't run into
anything!!
Best done on some ramp that isn't loaded with steel.

Bill Hale BPPP instructor a&p


On Apr 12, 8:22*am, Stealth Pilot
wrote:
On Fri, 11 Apr 2008 19:45:50 -0700, Road Dog
wrote:





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 ?


the problem doesnt seem to be the compass but some stray magnetism in
the aircraft.
swinging a compass takes about 15 minutes.- Hide quoted text -

- Show quoted text -


  #5  
Old April 12th 08, 05:11 PM posted to rec.aviation.owning
Drew Dalgleish
external usenet poster
 
Posts: 143
Default Compass trouble

On Sat, 12 Apr 2008 22:22:43 +0800, Stealth Pilot
wrote:

On Fri, 11 Apr 2008 19:45:50 -0700, Road Dog
wrote:

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 ?


the problem doesnt seem to be the compass but some stray magnetism in
the aircraft.
swinging a compass takes about 15 minutes.

Swinging a compass in 15 minutes may be possible if no corrections are
needed but to create a new card properly requires 8 points instead of
just 4. chasing stray magnetism can take up a lot of time. Unless you
have other reasons to believe that your mechanic is incompetent or
trying to screw you then I'd be inclinded to trust him.
  #6  
Old April 13th 08, 02:05 AM posted to rec.aviation.owning
Steve Foley
external usenet poster
 
Posts: 563
Default Compass trouble

"Road Dog" wrote in message
m...

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


Take a look here. I've only heard about it, never used it.

http://www.sacskyranch.com/degauss.htm


  #7  
Old April 13th 08, 03:15 AM posted to rec.aviation.owning
Jay Somerset
external usenet poster
 
Posts: 40
Default Compass trouble

On Sat, 12 Apr 2008 16:11:59 GMT, (Drew
Dalgleish) wrote:

On Sat, 12 Apr 2008 22:22:43 +0800, Stealth Pilot
wrote:

On Fri, 11 Apr 2008 19:45:50 -0700, Road Dog
wrote:

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 ?


the problem doesnt seem to be the compass but some stray magnetism in
the aircraft.
swinging a compass takes about 15 minutes.

Swinging a compass in 15 minutes may be possible if no corrections are
needed but to create a new card properly requires 8 points instead of
just 4. chasing stray magnetism can take up a lot of time. Unless you
have other reasons to believe that your mechanic is incompetent or
trying to screw you then I'd be inclinded to trust him.


If you look at a deviation card, I think you'll find it takes 12
points -- every 30 degrees, not every 45 degrees.
--
Jay (remove dashes for legal email address)
  #8  
Old April 13th 08, 11:38 PM posted to rec.aviation.owning
John[_9_]
external usenet poster
 
Posts: 103
Default Compass trouble

On Apr 11, 10:45�pm, Road Dog wrote:
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 ?



Sure you could take it somewhere else and spend the same or more money
for them to tell you the same thing. If your guy is conscientous
enough to notice the compass card is missing he seems pretty good to
me. It is possible for some of the steel parts in the aircraft to
become magnetized either through a lightning strike or even to pick up
magnetism through the ground just from sitting in the same spot in the
same way for years. That is more common on steel tube aircraft than
largely aluminum but is still possible.

I had a similar tough time swinging a compass in a Commander 114 which
has a large steel support bar just above the compass. Couldn't find a
degaussing devise but was able to get more powerful compensating
magnets which took care of the problem but virtually every point had 2
to 8 points of variation instead of the normal 0 to 5 or less. I also
once found an aircraft compass that had no magnets installed!

John Dupre'
  #9  
Old April 14th 08, 12:20 AM posted to rec.aviation.owning
Ron Wanttaja
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Posts: 756
Default Compass trouble

On Sun, 13 Apr 2008 15:38:49 -0700 (PDT), John wrote:

I had a similar tough time swinging a compass in a Commander 114 which
has a large steel support bar just above the compass. Couldn't find a
degaussing devise but was able to get more powerful compensating
magnets which took care of the problem but virtually every point had 2
to 8 points of variation....


Damn...Do you realize that a "point" on a compass is a bit over 11 degrees? So
your compass was 22 to 88 degrees off...should we start calling you "Wrong Way
Dupre'"? :-)

(or maybe we'll just assume you meant 'degrees')

My own compass-swinging adventure is at:

http://www.bowersflybaby.com/tech/hillbilly.html

There are certain advantages of Experimental category.....

Ron Wanttaja
 




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