Compass "Failure"

[ajudson]

Had an unexpected surprise last night. Just as I rolled onto the runway and applied full power -- assuming because the alternator was then providing the full 28v -- the center bar mounted compass began to aggressively spark and burn under the swiveling cover (circled in the attached picture). I'm not sure what exactly this cover is for (fuse for the compass light?).

I quickly aborted the takeoff and flicked the cover off to stop the burning. Definitely spooked my girlfriend for a little while.

The compass is an Airpath. Do I just need a replacement fuse (or whatever is under that cover)? A new compass? Or is there something worse I need to be worried about?

Thanks!

[LANCECASPER]

4 hours ago, ajudson said:

Had an unexpected surprise last night. Just as I rolled onto the runway and applied full power -- assuming because the alternator was then providing the full 28v -- the center bar mounted compass began to aggressively spark and burn under the swiveling cover (circled in the attached picture). I'm not sure what exactly this cover is for (fuse for the compass light?).

I quickly aborted the takeoff and flicked the cover off to stop the burning. Definitely spooked my girlfriend for a little while.

The compass is an Airpath. Do I just need a replacement fuse (or whatever is under that cover)? A new compass? Or is there something worse I need to be worried about?

Thanks!

There's a light bulb under the cover. A GE-327 if it's a 28v airplane,

https://www.aircraftspruce.com/catalog/elpages/gereplacement_11-04015.php?clickkey=17178

or a GE-330 if it's a 14v airplane.

https://www.aircraftspruce.com/catalog/pnpages/11-01950.php

[EricJ]

It's just a light bulb, but it shouldn't spark.   Something is up with it.   If nothing else you can just take the bulb out and see what was shorting.

[ajudson]

Thanks for the information! I will have to look into it closer when I get back out to the plane.

[GeeBee]

I've seen this before and usually it is vibration erodes down the solder dab on the bulb creating a shorting bulb. Change the bulb and it goes away.

[M20F-1968]

I have a compass that came out of a 1998 Ovation with 400 hrs total time.  I bought a flat-card compass.  The Ovation compass has been in my stash of parts meant to be put on E-bay but never got around to it.  You may want to mount it to the edge your your glareshield with a fiberglass housing that would be easy to make.

John Breda