Compass fails

[HansLab]

Suddenly my compass doesn't work: keeps pointing N or somewhat in that area.
(15 hrs testflight).
It worksed fine untill I added a Trigg 21 transponder. (Compass is located on top of the middle of the glareshield), testen with the tx off, as well: kept turning N.
Now I know how to swing a compass - and I could do so again, but: how did it come this far? Why is the thing working against all odds suddenly?
What would you do?
What would you think could be the source?

[Av8r_Sed]

Are either the control head or remote unit in close proximity to the compass? I might remove the cable to the control head to see if it has an effect. If not, I would temporarily remove the component closest to the compass to find if it's involved. Did any wiring get relocated during the installation? I can't think of anything else at the moment.

[Lion8]

Is there any induced magnetic field being generated? The fuselage chrome moly and is susceptible to being magnetized. There is a way to de-magnetize the fuselage. Just a thought.

[Dave S]

Hans,

Have you had any luck finding out where the sudden compass problem came from?

I remember when completing our KF, the compass location proved to be a major challenge.

Trying to locate it in the devil's triangle of magnetic demons in the middle of the cockpit proved to be fruitless in our case. Impossible to swing it at all. Impossible from the start. There are a number of older threads on the list regarding this issue and degaussing an airframe or relocating a compass.

I ended up placing the compass on the port side of the glareshield after finding that a small area at the port and starboard corners of the glareshield appeared to be free of magnetic demons. (see photo) Not ideal when flying out of the right seat; but, who uses the compass anyway when looking out the window? Also found that the SIRS compass was one of the best for adjustment - It has stayed correct within a correction factor of one or two degrees ever since installation.

If your's worked correctly at one time, a person would think it could be resolved? Had any luck?

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive
St Paul, MN

[jtpitkin06]

Let's start with the obvious and move to the obscure.

The last thing you added was the transponder. Remove the transponder from the rack to see if you get a change back to normal.

Then check the obvious...

Does the compass change heading with the battery on or off?
Does the compass change heading with the alternator on or off?
Does the compass change heading with the engine running or off?

If yes to any of the above, then you have an electrical current interference.
If no then you have a magnetic field or ferrous metal nearby.

Did you leave a flashlight with a magnet in the airplane?
Did you drop a magnetic pickup tool or screwdriver?
Do you have any magnetic catches, snaps, glove box latches, etc. added recently?
Got an iPad with a cover in the airplane? (magnet in cover)
Check your pockets?
iPhone case with a magnet?
New headphones?


Now for the obscure...

Does your compass have fluid in it?
Remove your compass and see if it works outside the airplane.
Borrow a spare compass and see if it also points north in the airplane.

Check your battery ground/earth for a secure and clean connection.
Check your battery positive for secure and clean connection.
Check battery contactors, relays, for tight connections
Try pulling circuit breakers, one at a time.
Disconnect the light in the compass.

this should give you a few places to look.

Let us know what you find.

John Pitkin
Greenville, Texas

[jiott]

I have wondered about my digital level with a strong magnetic base. I have used it a bunch of times during various parts of the build process, sticking it on the steel tubes here and there. I don't seem to have any issues with my ADHRS or whiskey compass, but still wonder if that magnetic level base could have caused any problems that remain after it is removed.