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Compass Woes

cplne

Registered User
When I bought my 12 it has the standard Airpath Compass mounted on the dash between the Vee Brace. It didn’t work at all, stayed on a heading of 060 and never moved. I contributed it to more junk and something else I would gave to address. Bought a Verticle Card Compass and the same thing it stays between 060 and 090. The mounting screws and nuts are brass, all the instruments are mounted with brass. The Vee Brace dose t appear to be magnitec but something is causing a significant disruption. Anybody else have this issue and what is your recommendation.
 
The V brace, and any other part of the cub airframe becomes magnetized to some degree. Also, the instrument panel generally has a lot of electrons and other moving parts. So the key to mounting a compass is to mount it high in the windshield, as far away from structure as you can.

i have had good success with the SIRS compass, mounted in the windshield.

MTV
 
Do you have a speaker installed? I found out from my C180 that the speaker magnet locked up the compass when I mover it up.
 
Second MVivion's recommendation. The SIRS is without a doubt the finest compass made. 4 compensating magnets instead of two, silicon dampening fluid and it has the best bearing possible.
 
Remove the compass or find another and move it around the area's tubing and whatever. If there's a magnetic node somewhere it'll point to it when close. Move the compass away from that spot. Vertical card compasses used to offer a couple of outboard magnetic correction balls attached to the compass case. I had them on one of my Cubs mounted behind the panel.

Then there's the Northland Aviation degaussing trick...hook an AC welder's clamps to the airframe near the magnetic node and a spot further away like the tail and briefly hit the switch. Might debug the problem.
 
Haven’t seen many (yes, I’ve seen a few) magnetic compasses work well in tube airplanes. If you look closely at numerous panel photos on his site, you can see up to 90 degree differences between the GPS track and the heading shown on the wet compass. When I was at Sun n Fun, I looked at all of the display aircraft from one manufacturer and not one compass was within 30 degrees. The rep stated they had very little luck with mag compasses. I remember the degaussing trick from Alaska in the 70’s and 80’s with limited, short lived success......
 
When I bought my 12 it has the standard Airpath Compass mounted on the dash between the Vee Brace. It didn’t work at all, stayed on a heading of 060 and never moved. I contributed it to more junk and something else I would gave to address. Bought a Verticle Card Compass and the same thing it stays between 060 and 090. The mounting screws and nuts are brass, all the instruments are mounted with brass. The Vee Brace dose t appear to be magnitec but something is causing a significant disruption. Anybody else have this issue and what is your recommendation.

Don't complain, most on this site have gray hair and their compasses say 270 most of the time

Glenn
 
Ironically, my compass is very accurate westbound.. and what little hair I have left is gray...
 
My compass came with my Cub in 1962. It sort of worked then, when I was much more proficient at "compass and a watch" navigation. It still sort of works, several diaphragms and gaskets later.

It is in the instrument panel, with steel tubes every which way. The Garmin 496 now resides in the overhead.

What I can't figure out is how Piper arrived at that deviation card. It bears little relation to reality. I have been party to several attempts to adjust compasses, and can only grin when folks suggest such activity.
 
When Radio Shack was in business, I bought a thing that was designed to erase tapes (I think). Ran the thing up and down all steel tubing in the cockpit and cured the problem on 2 different cubs. Magnetic and makes lots of noise when operating-degaussing. Still have it and recently used it on my ex-cub with amazing results.
 
Can also be done with the cables from an AC welder wrapped around the tubing.


Sent from my iPhone using Tapatalk
 
Degaussing works, but only for a period of time. Submarines are regularly degaussed. Same reason: movement through a fluid causes ferrous materials to become magnetized. As we all should know, the air is a fluid, just not as dense as water.

But, degaussing a Cub now (which is difficult to accomplish thoroughly) and soon it will return to its magnetized state.

As as I noted earlier, I have had good luck with the SIRS compasses in these and other planes. If I’m going to lug around a piece of equipment, it may as well function.

Anyone here ever experience GPS failure? I have. Nice to know which way is north in that case.

MTV
 
Mike, I agree completely. However, the amount of effort I’ve put in through the years has only been moderately rewarded. And, at this point in my life after 45 years of flying, if something is going to get me in an airplane I doubt it’s going to be a marginal wet compass. Don’t get me wrong, I think you should put effort into getting it to work and I still do. Just don’t worry about it too much..

Where did you put your SIRS in Your 11?
 
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Mike, I agree completely. However, the amount of effort I’ve put in through the years has only been moderately rewarded. And, at this point in my life after 45 years of flying, if something is going to get me in an airplane I doubt it’s going to be a marginal wet compass. Don’t get me wrong, I think you should put effort into getting it to work and I still do. Just don’t worry about it too much..

Where did you put your SIRS in Your 11?

The 11 is a no electric airplane, which significantly reduces magnetic influences. My compass is in the panel, and seems to work there. Installing an electrical system, most use the airframe as a “ground”, effectively installing a magnetic field in the airframe.

And, I’m not sure the 11 moves through the air fast enough to create friction......:roll:

MTV
 
I took your advice and just ordered one. Mine was (is) inaccurate and placed just right to tear my head apart if I hit something hard. I like knowing which way magnetic directions are too. I have 3 gps's (for animal tracking locations) and sometimes all 3 lose signal. (Not to mention the fact the magnetic compass is a required item) When it's in I'll try to post back in to say whether I love it or not, but thank you.. that's what makes this site so good in my view.. always a chance to pick up some useful information.
And check the bottom of your top longerons.. at the tailpost.. Sorry just had to say it again!
 
When I mounted mine it took about 3 hours of moving it around the windscreen to find a spot it would work well. I picked up some double side tape from local windshield shop to mount it. Lower right side of windscreen was best for my cub.
DENNY
 
A fuselage welded near the compass sensing radius with gas (acetylene and oxygen) is unlikely to have native magnetism unless the tubing was like that from the producer. However electrical wiring can create magnetic fields where activated (right hand rule - http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html). The compass will point to the magnetic Pole, or if stronger, a "pole of magnetism" in the airframe or wiring.

About 53 years ago I started spending time on marine vessels that had a compass...but they all had what were called binnacles (https://www.marineinsight.com/marine-navigation/what-is-a-binnacle-on-ships/) that included huge metal Monkey Balls adjacent to cancel any structure magnetic field. To expect an aircraft compass to be similarly calibrated (not a requirement - just a card on the panel with corrections done at some point prior) is folly.

Gary
 
When another pilot complained of speaker replacement cost, I gave him an old hifi speaker that would fit and had the right impedance. It bothered the compass because the magnet on the back of the speaker was a hockey puck compared to the thimble on the the certified.
 
Don’t forget, just forward of the firewall are 2 pretty strong magnets! The magnetos can play havoc on the compass.


Sent from my iPhone using Tapatalk
 
Here's the optional correction compensator I've used with both vertical card and standard compasses: http://www.aircraftspruce.com/catalog/inpages/compensator.php

It can be mounted directly to the flat rear panel of the units with screws or glued on or nearby. The magnetic balls are rotated to bring the reading within reason (~5*) then held with glue to prevent later rotation.

Gary
 

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