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#1
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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
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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
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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
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Compass trouble
On Apr 12, 10:07 am, Road Dog wrote:
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. Pipers sometimes suffer from magnetized engine mounts. I think it might have to do with the alternator ground cable terminals getting corroded so that the alternator ground current runs throught the mount tubing instead, magnetizing it and screwing up the compass. Dan |
#5
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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 - |
#6
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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. |
#7
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Compass trouble
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#8
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Compass trouble
On Sat, 12 Apr 2008 22:15:41 -0400, Jay Somerset
wrote: On Sat, 12 Apr 2008 16:11:59 GMT, (Drew 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) You're right Jay I was thinking 8 extra but that's obviously not what I wrote. |
#9
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Compass trouble
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