I tried to do a compass swing on a Citabria, but the compass won't move consistently on the ground.
It is an Airpath panel mount (that is mounted on the glare shield) and it looks relatively new. It is full of fluid and when removed from the aircraft it moves fine. I thought that it was possibly because it was not in its normal flight attitude so the owner took it flying and he said it still won't move.
Anyone ever have this problem before?
One AME said he has heard of airframes becoming magnetized.... and the compass wouldn't move.
Did you have your David Clark sitting on the dash right under it by any chance? Or a spoon or a fork? I have seen pilots snag the whiskey compass as U/S and then found there was metal / magnetic junk piled under it when I got to it.
Did you have the electrics off?
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Does a citabria have 2 tubular supports coming down on the glareshield? I had a tripacer one time that did the exact same thing. Bought a new compass too, with no fix. Not sure what it was now as it was too long ago, but as said earlier the airframe being magnetized would certainly do it.
If there was recent welding on the motor mount there is a good chance it was magnetized if they tig welded it. You can use compensating magnets to get it to swing good enough for your compass card. Your AME should know that. Tube and rag planes easily get magnetized if they are repaired using tig or mig instead of good old gas welding.
I know that you allready checked this. But if the compass is mounted with steel screws; you could have problems. Even some of the screws in a close proximity could cause a problem?
No, I tried all the obvious stuff, and nothing helped.
The owner just bought the aircraft and I just did the annual on it. I am a "King Air guy" so I have swung compasses lots but I have never had a problem with them. I haven't done much work on taildraggers or rag and tube planes though, so I thought maybe I was missing something obvious.
Thanks for all the help....I'll keep scratchin' my head....
The last time I flew was Wednesday 13 July, for my IFR flight test renewal. I arrived at the airport early this morning for a quick business flight to Toronto and found two things wrong with the plane:
1. there was a small but very strange-looking nick on one of the propeller tips; and
2. the magnetic compass was indicating north, but the plane was pointing southwest
I taxied the plane around in a circle, and the compass indicated within 30-60 degrees of north no matter which direction the plane was pointing. I had to scrub the trip, apologize to my customer, and plan on joining the meeting by speakerphone.
Just before I left to head back to my home office, the owner of our local shop arrived and came out to take a look — the first thing he noticed was that corner of the propeller tip was not nicked but melted, as you could see both from the shape of the metal and from the slight paint blistering around it. That, combined with the apparent demagnetization of the mag compass, suggests that the plane took a lightning strike. We looked around, but couldn’t find any other damage (usually there’s an exit mark somewhere on the airframe, especially near the tail).
After investigation and careful consideration, I’m fairly certain that the prop strike happened on the ground, and not during my previous flight on 13 July. In particular, the damage was on the higher prop tip (as the plane was parked), we were over 25 nm from the nearest storms and in VMC during my 13 July flight (with a designated flight test examiner on board, no less), and a line of very severe thunderstorms passed through Ottawa a few days before I discovered the damage, with lightning hitting one man in a Kanata parking lot.
More info
I just stopped typing this post to take a phone call from my shop. One of the mechanics called Sensenisch (the propeller’s manufacturer), and Sensenisch said that after a lightning strike the hardness of the metal for 18 inches or so of the blade can change — it looks like the propeller might be coming off the plane and heading to Carp for non-destructive testing, and I might be on the phone to the insurance company. Next to total structural failure or a fire, a broken propeller blade is just about the worst thing that can happen in flight, so I’m not planning to play around with this one.
Take the metal end of a tape measure and deflect the compass 2 degrees. After you remove the tape the compass should come back to the original heading. Try this on each of the cardinal headings. If it doesn't return to the original heading, the jewel bearing is probably toast and the compass should be replaced. This happens if the a/c vibrates significantly. You can do the test again with the compass pulled and make sure its still u/s. I had one compass that this was a real problem on East, and I couldn't swing it.
and it looks relatively new. It is full of fluid and when removed from the aircraft it moves fine. I thought that it was possibly because it was not in its normal flight attitude so the owner took it flying and he said it still won't move. 
