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Compass trouble

Did you know that you can use your wristwatch for a compass as long as you can find the sun? Align the sun half way between the hour hand and 12. 12 will be south, 6 will be north etc.
 
skywagon8a said:
Did you know that you can use your wristwatch for a compass as long as you can find the sun? Align the sun half way between the hour hand and 12. 12 will be south, 6 will be north etc.
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I long forgot about that.
 
Looking at the sun......assuming you can see it, of course. You guys never fly on cloudy days? Hence the term “Fair weather flyers” I guess.

And in summer at least, in interior AK, the sun is pretty much straight up. :p

MTV
 
stewartb said:
My Apple watch has a compass! ;)
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How does it work? Is it just a magnetic compass? GPS? My old iPhone also has a compass (with built in level). Never thought about trying it out in the plane. Going to the next time I fly. Those of you using iPads or tablets, do those have a compass? If so, would be interesting to see how that compares to whiskey compass in panel.

Jim
 
My phones and LG tab have to the best I can tell are GPS driven compasses. I need to check my Koyacera phone though.
Two of my older Garmin handheld GPS have magnetometers in them as well as the Mitsubishi Montero I drive also does. I find it interesting that the Montero's compass even works since I would consider it to be a 4K lb magnet.
 
As others have indicated, I believe that magnetism of the steel tube fuselage is probably your issue. You can find and quantify magnetism on a steel tube fuselage.

I have an iPhone with a 99 cent application called Smart Tools Pro. It has a number of functions like protractor, level, compass, etc. One of the functions says MAG FLUX.

So, I set the Smart Tools APP on MAG FLUX, and was able to pin point what part of a steel fuselage tube caused the magnetic disturbance. I mean, a normal reading on MAG FLUX is less than 50. When I moved it near the violating tube, it went up to 800. Its so sensitive that I can identify where my phone has its magnetic sensor. If I move the phone near a magnet, it will go double that number. A Boy Scout hand compass will point to an offensive area, but the MAG FLUX iPhone app will find AND quantify the offensive area.

Then I used an old 115v AC Weller soldier gun to degauss the tube. We'll see if the magnitism returns.

I wasn't able to get the tube down to 40, but degaussing it helped a lot.

Lastly, I used the MAG FLUX iPhone app to locate a point for the compass where I have a reading of 45. For my Bearhawk Patrol, I found a windshield mount ideal. It coincidentally places the compass the max distance from fuselage tubing. The top of the dash was also acceptable.

I'm still building. I went with the SIRS compass because of feedback I got on this forum.
 
I drank the kool aid. I bought a SIRS panel mount compass for the Wildcat. Junk. It went in the trash before it went in the plane. Don't believe everything you read!
 
bcone1381 said:
Then I used an old 115v AC Weller soldier gun to degauss the tube. We'll see if the magnitism returns.

I wasn't able to get the tube down to 40, but degaussing it helped a lot.
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That's something I'd like to hear more about. I was wondering if one could use an AC welder to degauss. Using a soldering gun sounds interesting.

Vic

Sent from my SM-J320V using SuperCub.Org mobile app
 
stewartb said:
I drank the kool aid. I bought a SIRS panel mount compass for the Wildcat. Junk. It went in the trash before it went in the plane. Don't believe everything you read!
Click to expand...

I'd like to hear more. Most guys seem to like them. What, specifically, didn't you like?

Web
 
That it couldn't identify north played a big part. And that before being installed in an airplane.

This talk about a compass being more reliable than electronics is comedy to me. Whiskey compasses come in two flavors. Bad and worse. In the Cessna I'm still in the habit of setting my DG fairly regularly. I set it by my GPS. The compass is along for the ride.
 
For a few years I had a Whiskey compass that worked at several headings. I eventually tried a vertical card compass that always showed east. Having remembered being on large vessels with compasses corrected with magnets I found a place on top of the panel where two small magnets corrected the compass. It worked until I started the engine, and I was back to looking for the magic spot for both magnets. Eventually I found the spot That worked until I was flying at cruising RPMs. Not sure if the problem was the Rpms or the tail up attitude, but eventually I found the spot that gave me correct headings at cruise RPMs. Now with a left hand door, a seaplane beefup, reinforced motor mount, and a larger engine, I’m back to showing east regardless of heading. Have become complacent about magnetic compass after using Foreflight and Garmin Pilot. With all thats happening these days should be ready when “the powers that be” mess with selective availability. One of these days Ill mess with the magnets again. I used tape to hold magnets in place while I was looking for the sweet spots.
 
I too have found compasses to be inaccurate. I had a Stinson SR in which the compass read 330 degrees, no matter which way the nose was pointed. The solution was to place a marine compass on the floor behind the pilot's seat where it was accurate.

Some airplanes (DC-9) have the compass remotely mounted then use a couple of mirrors to see it.
 
stewartb said:
I drank the kool aid. I bought a SIRS panel mount compass for the Wildcat. Junk. It went in the trash before it went in the plane. Don't believe everything you read!
Click to expand...

Who said a SIRS panel mounted compass was going to work? If you don’t understand even a bit about magnetism, of course you won’t be successful getting a compass to work.

MTV
 
Wherever the compass points north (when it's not true north) in the plane wouldn't that be the magnetized spot? Like reading east all the time would mean the local hot spot is left of the compass.

Gary
 
BC12D-4-85 said:
Wherever the compass points north (when it's not true north) in the plane wouldn't that be the magnetized spot? Like reading east all the time would mean the local hot spot is left of the compass.

Gary
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That gives you a general direction. But if you take the compass out and carry it around you can pinpoint just where or what is magnetized. When I had the fuselage I am building outdoors I went around it with a compass, all seemed fine. When I held it inside the aft section of the fuselage it locked onto straight ahead. Interesting though when I held it near where it will mount it seemed fine. So I mounted it screwed to some wood near where it is to go. Picked up the tail and walked the plane around in circles, the compass was just fine. Unstrapped the wood and placed the compass back in the aft section and it faced forwards even when walking the fuse around. Be interesting to see what comes of this as I proceed.
 
Yes CharlieN it's a good experiment and hope it works. I had similar in a PA-18A. The compass was in dog point mode with a repair weld on the upper firewall/V-brace joint. Mechanic said let's rid the demon by degaussing so put an AC welder's clamp's on the spot and tail. He briefly hit the ON switch then retested the compass. It was better and I flew it like that with a Hamilton vertical card compass with their compensating ball kit.

Gary
 
I tried Using a degaussing coil on my cub did not seem to help much spent three hours moving the Compass around the wind screen finally found a spot that actually works pretty good it is not perfect but does a general direction ok.
DENNY
 
My vertical card compass is very close to accurate. I use it as a cross-check from GPS track, and to get an idea of wind direction / speed. It's between tubes near the left-fwd spar fitting mounted with Adel clamps. Everywhere else from the front seat it was extremely (and exasperatingly) reliable. Because it ALWAYS pointed east.
 
Gordon Misch said:
My vertical card compass is very close to accurate. I use it as a cross-check from GPS track, and to get an idea of wind direction / speed. It's between tubes near the left-fwd spar fitting mounted with Adel clamps. Everywhere else from the front seat it was extremely (and exasperatingly) reliable. Because it ALWAYS pointed east.
Click to expand...

Gordon> science is about trying stuff to see what happens > hey Gordon where is the magnetic node?

Gary
 
Gordon Misch said:
Sorry Gary, I'm not familiar with the terminology??
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I was just wondering if there's a magnetized spot or node in your plane you had to avoid or minimize by the final location of the compass?...that created the "Always East" condition you mentioned.

Gary
 
Ah, ok. I originally had the vert card compass in the panel, and it swung within a couple degrees in all quadrants. But gradually over time that changed. "North" was always to the left and "East" was always straight ahead. So the residual airframe magnetism at that location was significant. I purchased a SIRS, but it did the same thing. I purchased the compensating balls for it, but nothing I was able to do would make it usable. So I returned it and went back to square one with the vertical card unit. I held it in my hand "everywhere" in the cockpit trying to find a location of minimum interference. Up at that left-hand fwd spar cluster was the best, so I made an aluminum bracket. I was able to get it very close to accurate with its internal compensating magnets, and it swings very close to correct now. So I guess the direct answer to your question would be the worst area was in the vicinity of the panel.
 
Thanks Gordon for the description. I used "node" instead of typing centering point for the magnetic attraction in the cockpit. Is it related to the plane's electrical activity or still an attractant for the compass when the systems are shut down...like a weld or magnetic source?

If it changed over time was there a new component installed? If not maybe there's a magnetic field surrounding DC electrical current. Not uncommon as even the Earth has a current loop: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/MagEarth.html

Gary
 
Actually, I gave that considerable thought as I was wiring the plane. I bundled wires that were anywhere close to the compass behind the panel such that their magnetic field vector would be vertical in the vicinity of the compass. The intent was to not interfere with the horizontal component of the earth's field. At first, it was great, but like I said, gradually degraded and was independent of radio, lights, etc being on or off. I don't know why. Maybe high current fore/aft wiring, like for starter or alternator had an influence on the frame even though at a distance from the compass. I considered degaussing, but decided against that effort because whatever caused the problem would undoubtedly reassert itself.
 
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