1966 M20E Compass Problem

[A64Pilot]

On 8/25/2023 at 9:47 AM, Fly Boomer said:

Please heed the advice from @bcg above.  Any kind of electrical device used inside your airplane has the potential to create as many problems as it cures if not used properly.

It’s just a big electromagnet, simple thing, but you need the little swing needle meter to see when to stop.

We had to de-gauss every airframe and still I couldn’t get 1 in 3 compasses to swing so the cockpit needed it again.

You need to get one of these things

https://www.amazon.com/MAC-DET-Magnetism-Detector/dp/B00E0LGAQ8/ref=asc_df_B00E0LGAQ8/?tag=hyprod-20&linkCode=df0&hvadid=312350426635&hvpos=&hvnetw=g&hvrand=11138029211919500577&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9011535&hvtargid=pla-502262342865&psc=1

A lot is Stainless steel is actually magnetic, cold working and welding can make at least 300 series SS magnetic, or not it literally depends on the piece.

[A64Pilot]

I’ve swung hundreds of compasses in the Army and on new aircraft.

But I have never seen one that would stick on one heading, not even close, worst I’ve seen was ones that you could adjust within tolerance.

Makes me wonder what going on with yours?

[Fly Boomer]

3 hours ago, A64Pilot said:

Makes me wonder what going on with yours?

Unless there is some kind of super magnet close by that captures 100% of the attention of the compass.

[EricJ]

30 minutes ago, Fly Boomer said:

Unless there is some kind of super magnet close by that captures 100% of the attention of the compass.

I've had that happen, but usually while driving/offroading.    I've never had it happen in an airplane, fortunately.   

[N9335M]

Thank you all for your feedback. I bought an $11.99 degausser from Amazon. I kept it far away from my compass and ran it along the center post. The compass is now free swinging and is right on. Now, once I get the elevator counterweight inspection taken care of from the AD, I'll be airworthy!

[ArtVandelay]

Thank you all for your feedback. I bought an $11.99 degausser from Amazon. I kept it far away from my compass and ran it along the center post. The compass is now free swinging and is right on. Now, once I get the elevator counterweight inspection taken care of from the AD, I'll be airworthy!

BTW, at the risk of being obvious, keep it away from your magnetometer if you have one.

[N201MKTurbo]

1 hour ago, ArtVandelay said:

BTW, at the risk of being obvious, keep it away from your magnetometer if you have one.

Will degaussing hurt anything? This is a tough question since it is impossible to imagine every conceivable system arrangement that could be subjected to degaussing. In all our experience we have never had any electronics device hurt by the degaussing process. This is because the induced voltages from the degausser are low, and the electronics components have a fairly high impedance at low voltages. It would be safer to degauss electronics while the power to the electronics is turned off in case the small induced voltages cause the device to operate incorrectly. It is always safe to degauss any of Geometrics’ manufactured equipment (including the sensor). On the other hand, here are some things to consider when degaussing some types of objects. Large conductive planes or rings will have large circulating currents induced in them by the degausser (but the voltages are still very small). This induced current will produce an opposing magnetic field that will fight the degaussing field – causing both the degausser and the conductive plane/loop to vibrate substantially. If the device being degaussed is sensitive to this vibration (intricate mechanical workings and the like) then this is a possible route for causing some damage. Also, sometimes objects being degaussed have embedded magnets that are necessary for the device to operate properly. A good example is a device with a permanent magnet speaker inside. Generally it is hard to degauss a magnetically hard permanent magnet, but the degausser is strong enough to at least partially do the job. A partially degaussed speaker (or other object that requires a magnet to work right) isn’t going to work the same as before – so be aware. [Things that have magnets in them shouldn’t be used near magnetometers anyway.]

https://www.geometrics.com/support/magnetometer-degaussing/#:~:text=Degaussing misaligns magnetic domains so,are not sufficiently magnetically randomized.

 

While the degausser may demagnetize the compass needle, I don't see how it would hurt the modern solid state magnetometer. They use hall effect devices, which are not magnetized and should dutifully measure the fields from the degausser without damage.