Whiskey compass gone bad

[Speedo]

After a PulseLite system was installed at my last annual, my whiskey compass deviated 15 degrees any time the PulseLite was turned on. Since I almost always flew with the PulseLite turned on, the compass was almost always in error by 15 degrees.

More recently the compass has become permanently fixed at an approximate heading of North. My guess is that the PulseLite electronics have magnetized the tubing in proximity to the compass, and that there's nothing wrong with the compass itself.

Can anyone recommend a test that will prove, or disprove the theory that the PulseLite is generating a magnetic field? If the PulseLite system has magnetized the tubing, can I shield its wiring or its electronics to prevent it's magnetic field from perpetuating the problem?

 

[Rv8tor]

What you need is a gauss meter. It is very simple to use. Any shop that does magnaflux inspections on engine cranks for example will have one.
Just run the gauge along the surface and watch for needle deflection either positive or negative. Nothing to it. :lol:

 

[mvivion]

I had similar problems with my cub. Installed a Hamilton vertical card compass, with compensator balls from Aircraft spruce, took care of the problem.

Most Cubs have some issues with compasses, due to some magetizing of teh airframe,

MTV

 

[Sam Beckett]

Yeppers me too..

I had the same dern problem too....till I quit drinkin the whisky out of it..Its alway better that the compass go bad than the Whiskey in it...

 

[cubunltd]

I always mount the compass near the top of the windshield, Actually on the windshield. No more problems.
cubsunlimited@verizon.net

 

[cubdrvr]

There has been a lot of posts on this. From my experience it is extremely difficult, in a cub, to achieve the 10 degree limit imposed by the regs....and not worth the hassle to do it. I've written down the indicated compass readings while on the 8 major headings ( in case I need them ) but use the panel GPS entirely for navigation.......with a portable GPS backing it up.

 

[cubunltd]

Like I mentioned earlier, Mount the compass at the top of the windshield, approximately 5- 6" forward of the front carry through spar. I use the S.I.R.S. "NAVIGATOR" compass sold by Aircraft Spruce. Be sure and order the short mounting leg as it's extra. The compass is small and made to read easily from the overhead position. It's accurate and being in the windshield, it's removed from any magnetic or electrical interference.
Hint: Don't run the landing light wires across the front carry through spar like original. Everytime you turn on the lights, the compass will swing about 10 degrees.
I've usedthis compass and mounting positionon all the cubs I build and no one has had a problem. they all work.
cubsunlimited@verizon.net

 

[Ursa Major]

cubunltd,

Sounds like you are using an adhesive to fix the compass mount to the windshield. If so, how does it hold up in cold weather (freeze thaw cycles)? Is this a log book entry for installation or is the process subject to STC/FA? I know rear view mirrors on cars are glued to the windshield so I'm guessing that the adhesive is similar.

 

[cubunltd]

The compass comes with the adhesive on the standoff. So far it's held up . I have also drilled 3 small holes through the plastic bracket and the windshield and made a small aluminum doubler for the outside and attached with # 6 stainless screws. I did this on the first couple and then just glued them in place. So far none have come off. We are doing log book entries as this is considered a minor alteration by my FSDO.

John
cubsunlimited@verizon.net

 

[d.grimm]

Compass and pulse lights

Just put new panel in my PA22/20 (Woolsey panel) and put the vertical card compass in the panel. Partner just started complaining after a month that the compass is way out. Found out today that when I turn pulse lights on I get a 40 degree error. Glad the GPS gives heading.
Dave

 

[glassjet]

I have heard that after airplanes have been drilled on and ground on after several rebuilds they develop a "magnetic field" built into the frame... and have to be de magnitized.... can't remember how they do it.... read about it in an old aircraft maintenance magazine....

 

[glassjet]

Do you like the vertical card compass? does it act like a normal compass? (turn the opposite way of the turn and such) Have thought about putting one in but not sure if it would be worth it?

 

[d.grimm]

Vertical Card Compass

I think they are great. Operate just like a miniature modern Directional Gyro. They still have accelerate north, decelerate south errors.

 

[Speedo]

I contacted Pulse Lite, and they indicate they have seen this problem once before in an R22 helicopter. They suspect the culprit is the wire leading to the landing light. So, is there such a thing as shielded wire for this sort of application??

 

[T.J.]

delete

 

[wlt]

Compass

Replaced my panel mounted compass which always indicated 030 degrees even when headed to Fla. w/a SIRS Navigator about 4" ahead of the front carry-thru on the right side. Made a mount reaching forward w/ two screws from the back of the channel above the carry-thru as the adhesive gave up. It is great- maybe 4 degrees off worst heading. Been there more than a year & couldn't reccomend it more as it really works.