Compass Install

[Dick B in KY]

Need some opinions on compass install. I have a Dynon D100 EFIS system, but for a back up I'm installing a pedestal mount compass. Question is where on the glare shield have most people installed their compass? Seems the front area on my aircraft is loaded with residual magnetism that I cannot subdue. What problems have others run into in this effort and your solution.

Thanks,
Dick B

[HansLab]

Good question! And, since I am in the same process of build: how do you people attach a compass on a glare-shield...?

[Dave S]

Guys,

I think this is a very common challenge with an electrically welded airframe....meaning the magnetic demons.

My airframe was infested with many, many magnetic demons.......tried to put the compass in the middle of the glareshield or hang it from the carry through tube - no good.........best calibration was only 170 degrees off........although we are accustomed to having the compass in the middle, decided to forgo that convention and put it where it would work instead. Couldn't find any regulation requiring placement smack in the middle.....

Through experimentation I found that the only place it would work is on the left or right side of the glareshield in a very small area not affected by my micro-devil's-triangle. Was able to adjust it to within a couple degrees so if the minor correction from the CCC is applied it is right on in any direction. Works equally well on the right or left side of the glareshield but opted to put it in front of the pilot.

Photo attached.

To mount it on the glareshield, I fabricated a mahogany block (Lacquered to match the glareshield and interior), conformed to the glareshield profile and the outline of the compass base. Screws up through the glareshield and down through the compass mounting base. If a person wants to make it lighter than its 1.5 ounces, one could route out the center of the block. The SIRS compass has a hinge on the mount that makes leveling the compass easy.

The compass I used was one identified as SIRS....highly recommended by John Mc Bean.......I concurr.....very precise adjustment and I couldn't be happier.

Others tell me that degaussing the airframe is a possibility, but, that should be done before anything is assembled. Degaussing is kind of artsy voodoo, approaching an act of exorcism.

Another person asked if I could find my way without a compass...."sure"....OK then put it anywhere you want and ignore it.

Sincerely,

Dave S
KF7 Trigear Flying
912ULS Warp Drive

[Dorsal]

I did not install a compass but did put the magnometer in the wing tip as the Instrument pannel was infested with magnetic gremlins.

[HighWing]

This discussion has been talked about over the years. I have no personal experience with the following, but brighter minds than mine have discussed degaussing the airframe. Many have done it after the panel was installed, but there can be some issues with using them too close to certain instruments and avionics. There are commercial and home brew degaussers that will reduce the residual magnitism from the aircraft tubing. For those just starting the panel, it might be a good idea to trial fit the bare panel and the glare shield and see what you have with the compass in the desired location. Degaussing then wouldn't cause issues with other instruments or avionics. It is the very slight magnetic effects of the current flow in the wiring that the adjustment screws are designed to compensate for when swinging the compass. I read of one guy who had so much magnetism in his airframe that the compass wouldn't swing at all - degaussing cured the problem.
Lowell

[jtpitkin06]

Degaussing the airframe is not a dark art only cured with a spell from Hermione Granger at Hogwart’s. It’s really quite simple.

Get a bulk tape eraser. A search for “bulk tape eraser” will get you many results. Radio Shack doesn’t sell them anymore, but you can find them on the used market or eBay for under $30. It looks like a small travel iron with a rectangular base and a spring loaded switch on the top of the handle.

Hold the power button in the on position as you move in toward the airframe and move the tool in a circular “ironing” type motion. Get as close to the metal as you can without letting it clamp onto the metal. I often use a scrap of corrugated cardboard as a protective bumper. Do the inside and outside of the frame several times. Let the tool cool if it starts to get hot. Don’t worry if you can’t reach some internal areas. These tools are powerful enough to treat the frame from the outside.

After the treatment, bring your compass up to the mounting area on the panel. If it swings wildly, move the compass away and treat the airframe some more. It may take several treatments to eliminate the gremlins. When you think you have it under control, turn the aircraft 90 degrees and check the compass again. A final treatment or two may be required.

For my airframe it took probably five or six complete treatments, each taking several minutes with cooling time for the tool. I spent maybe two hours doing the total degaussing. Prior to treatment the compass would only read South.

John Pitkin

[Esser]

John, you are full of great tips all the time.

[chefwarthog]

If i got a Dynon SkyView system with 2 fully redundant ADAHRS: ( a ADAHRS is a complete MEMS-based attitude reference and air data computer, integrated with a digital compass.) Do I have to have a compass install in the plane too?

[Dorsal]

I don't think so but you will need to run the Pitkin process as there is not a remote magnetometer for the Skyview.

[Esser]

JF, in Canada you have to have a compass or a magnetic direction indicator that is independent of your electrical system.