Light Aircraft Association

I am having trouble swinging the compass in our RV9. The compass works fine out of the aircraft but moves significantly when fitted. So much so that I cannot bring it back to a sensible error margin when following the manufacturers procedure to adjust.

It is mounted on the vertical tube supporting the front screen which I suspect has become magnetised. Can this be degaussed and if so how does one get hold of such a device.

Failing this, what are the implications of using an electronic solid state compass. Is this allowed?

Regards

Mark,

On another (US) forum regarding degaussers:

"I would start out by degausing the airframe tubes in and around the windshield. Find an old TV repairman with a degausing coil that was used as regular remedy for magnetized TV video tubes. It is about 600 hundred turns of #26 laquered magnet wire plugged into the AC wall socket. You turn it on and start close to what you want to demagnetize rotating the coil facing the tubes and moving in a circular manner with the coil facing the tubes. Walk away from the airplane while doing this and when you are 10 or 15 feet away turn the coil perpendicular the airframe and turn the coil off.

I made one by wrapping 600 turns of magnet wire around a GI S--t can, wrapping the coil with friction tape, adding a momentary push on switch and ac plug. "

Also, some info on a vertical compass and compensation etc:
http://www.cumulus-soaring.com/preci...n_MCCI-102.pdf

Hope this helps

Tony

Damm!!
I just got rid or my old TV repair kit, which included a degausser. Decided that I would never repair a CRT again, and didn't consider other uses

Seem to be able to get them on ebay for not a lot of dosh

mb2

This is probably a silly question – what sort of bolt are you using to bolt it to the airframe?

Rod1

Hi Rod,

The attachment bolt in Non Ferrous as supplied with the Compass (SIRS Navigator)

Thanks for the reply

Regards

mb2,

I have a Heath Robinson degausing rig made from CRT degausing
coils. Where abouts are you in the UK?


John

mb2

That is odd. I have the same compass and did not get a bolt with it. My first “non ferrous” was not so much, but the second attempt solved all my issues.

Rod1

The aircraft is based 6 miles west of Tatenhill (EGBM) in Staffordshire on a farm strip.

Regards

Remember to remove the compass before degaussing!

mb2,

I'm Essex based so a bit far off to travel over.
Please see your PMs

John

I had the same problem in my RV6 (sliding canopy), with the same compass (a lovely piece of kit).

The centre strut that the compass attaches to was magnetised in no uncertain terms! According to the compass I never went more than 30 degrees away from a northerly heading, no matter what I compensated the compass to. I removed the tube from the airframe (tricky, but possible) and demagnetised it with a degausser I bought from a machine tool suppliers (www.rdgtools.co.uk, I think).
I also used the degaussser on the rollover bar / screen support and canopy frame. The support bar took several attempts to demagnetise, but that may be my technique.

As already stated remember to remove the compass first.
Also, remove any instruments from close by on the panel. A surprising number of instrument contain magnets to my certain knowledge (mechanical tacho, some electric engine instruments) and I would guess that some others (VOR indicator, vacuum gyro instruments, radios, GPS's) might not like being placed in hefty magnetic fields either. Given the price of kit and the time taken to remove it I opted to take it all out!

When it comes time to put it all back together and swing the compass take a squint at the instructions for the compass. You'll probably need to remove the top plate and set the adjuster magnets back to their 'default start' positions