compass placement

jon s blocker · Post by **jon s blocker** » Wed Feb 12, 2003 7:53 pm

I'll break the ice on the no new posts with a question. I am putting in a center stack panel in our '53 B, and would like an opinion on where to position the compass. Would it be better to place it "in the panel", or "above the panel"? Will there be swing problems if it is placed in the panel? I can't put it on the w/s strip, as it will be a one piece w/s. How about some opinions. Thanks,
Jon

doug8082a · Post by **doug8082a** » Wed Feb 12, 2003 9:35 pm

I would think that "in the panel" would lead to swing problems. My '52 has it mounted on top of the panel - is that an option? I wonder if there's any way to attach it to a bracket that attaches to the piece overhead where the top of the windshield meets the fuselage... kind of like some older car rear view mirrors? The bracket could extend forward and down enough to place it in view... sort of taking the place of the old center strip? Just a thought... don't know if it makes sense or not.

JDH · Post by **JDH** » Wed Feb 12, 2003 10:00 pm

I also have a '52 and mine is mounted on top of the panel. With the visibility the 170B offers, that has never been a problem. Also, I have sat in a few airplanes with the compass mounted by the top of the windshield/headliner "Ã la rearview miror", I find that that can get in the way of sunvisors and is not part of a natural scan. As for panel mounted units, I think the scale of opinion favored not to do it. JD

lowNslow · Post by **lowNslow** » Wed Feb 12, 2003 11:47 pm

I believe you can still put it on the windshield, which is probably the best spot, with a mounting block. This is a plastic block that glues to your windshield. This should be available from the windshield manufacture.

wa4jr · Post by **wa4jr** » Thu Feb 13, 2003 2:28 am

Mine is in the panel....I thought they were all originally mounted there. I have a '54. It would seem logical to have possible swing problems with the compass down in the panel among the instruments. Mine is currently out of whack and I have the kit to rebuild it. I will attempt a swing and see if it works. If I had my druthers, I'd mount it on top of the panel. Would gain another valuable 3.125" hole as well. I thought about dropping it down from the overhead as has been mentioned, but it would sure would not want the imprint of that compass in my forehead in a turbulence encounter!

frainiea · Post by **frainiea** » Thu Feb 13, 2003 3:40 am

I am in the process of replacing my windshield with a new one without the support stripe. I had a vertical card compass hanging from strip. Precision Air has a dampen mount for this purpose. My problem seems to be that if I hang it from the cross beam it is moved so far aft it is difficult to pick up in my scan. Fortunately I can flip the PA hanger over and I plan on building a jig to mount it on top of the instrument panel but pushed back as far as I can manage. My two cents is to have a buddy hold it where you think it should be and see how it fits your scan.

Having read the previous posts makes me wonder if mounted an inch above the deck will remove it from the panel enough to avoid the problems being discussed for an in panel mount

zero.one.victor · Post by **zero.one.victor** » Thu Feb 13, 2003 6:13 am

I have the "two-piece" windshield (one-piece with center-strips) and the compass bracket mounts off that,very close to the top of the panel. Even if you're going with the "one-piece" windshield (no center-strip),what's wrong with using the same type bracket & mounting the compass to the windshield--drill 2 holes and bolt her up? Seems like a big hassle to make up a new bracket to mount to the top of the panel,that's just gonna do the same thing in the same place.

Eric

6886 · Post by **6886** » Fri Feb 14, 2003 2:34 am

I have a 56B. The previous owner relocated the compass on a bracket attached to the windshield strip, about 6" above the panel. I have zero calibration errors radios on or off. The old rectangle where the compass was now contains the remote controls for the ELT.

wa4jr · Post by **wa4jr** » Sat Feb 22, 2003 11:02 pm

I pulled my compass out today for a rebuild. I am thinking of fabricating a heavy aluminum "L" bracket and mounting the compass to the top of the panel instead of putting in back in the panel. My only worry is vibration. I am somewhat afraid that the compass may vibrate too much if mounted the way I intend. Comments? I also wanted to replace the light in my compass only to find out that it is apparently an unlighted model Airpath #CB-2100-3. Guess I'll have to put a light ring around it when I install the rings on my other instruments.

Post by **GAHorn** » Sat Feb 22, 2003 11:37 pm

Go talk to your local instrument shop or A&P and I'll bet they have an old compass they'll let you have the lighting socket out of. Be certain to twist the lighting wires together like safety-wire so to nullify any magnetism from the DC current in them, or they'll influence the compass.

Dave Clark · Post by **Dave Clark** » Sun Feb 23, 2003 12:07 pm

John
I have a vertical card mounted on the glare shield where you're contemplating mounting yours. It has small grommets where the screws go through plus a 1/4" foam on the base all of which is fairly loose. It allows for a lot of vibration dampening. I like the location.

funseventy · Post by **funseventy** » Mon Feb 24, 2003 7:49 pm

I think its personal preference. Why spend the money on a 1 piece windshield and then mount a compass in the middle of it? Why risk drilling two holes in it where it could crack? The top of the panel would not hurt visibility, but you could look at leaving it in the panel. How much do you use it? I believe that mine is only in there to please the feds. Mine is in the panel and works good enough for me. I would assume you are installing some form of GPS and then the compass isn't much after that. Unless of course you are flying such hard IFR that a couple of degrees hurts you. But remember if you are using your compass to set you DG while on the ground(sitting 3-point) you've already incorporated error. If you do a compass swing and don't level the tail and turn on avionics you are writing down errors. So it sounds like a compass is inherently unreliable based upon too many human errors. So you can probably get it close enough while keeping it in the panel and avoiding head injuries.

That sounds like more than two cents worth, but its probably half that.
Kelly

wa4jr · Post by **wa4jr** » Thu Feb 27, 2003 2:16 am

UhOh...tell me more about swinging the compass with the tail up. I was just going to taxi back and forth across the compass rose for the swing. Are you saying that a wet compass does not indicate accurately when the tail is on the ground?? AHA! Thanks George! I shined a flashlight around the front of my compass and did indeed find the void where the light socket is apparently mounted on the front top of the case. I'll look for a socket. One more thing. I was going to rebuild the compass, but it is not leaking and appears to swing free. When level, what is the proper fluid level? Mine is about 1/8" below the top of the glass. Do you add the fluid by removing the hex nut on top of the unit? Yes, leaving the compass in the panel would be easiest until I need the hole for something else. Since the compass was originally mounted there, I suppose it can be swung to read accurately while in the panel with all the metal and wires around it. Comments and ideas?

Post by **GAHorn** » Fri Feb 28, 2003 4:28 am

The typical Airpath compass can be repaired by purchasing a compass repair kit from Aircraft Spruce or SanVal.
It consists of fluid (about a pint, but the compass actually only holds about 3 oz), a paper gasket for the front of the glass, and a rubber gasket for beneath the glass, and a rubber diaphragm for the rear of the case.
The compass is rebuilt by using a small bowl to catch fluid in, and removing the rear sheet-metal dome (4 screws) and the front glass.
Note: The front glass is bevelled (see the straight edge and note how it's bevelled front-to-back.) Note how it's installed as to which side faces out. Handle the glass with care as it's exceptionally brittle and it's edges may be easily chipped.
Replace the diaphragm and rear dome, then submerge the entire compass in a bowl of fluid with the window facing up. This fills the case completely. Install the rubber gasket, window, and paper gasket and frame with the window facing up. This prevents any air bubbles from being inside the compass.
The purpose of the diaphragm is to allow expansion at altitude/hot days.

Swing your compass at an aiport with the tailwheel upon a table or sawhorse to level the airplane and with the controls in the centered and nuetral position with the elevator also nuetral. The engine should be idling, radios on, and the electrical system energized except for large temporary loads like landing lights. Remember to use at least 4 cardinal points when swinging the compass (N<S<E<W) adjusting out 1/2 the error at each point. Then check them all again and make a correction card.

PS. Compass fluid is a specific type of non-flammable naptha. Some old-timers substitute safety-solvent or kerosene, but both will "yellow" the compass eventually.

Dave Clark · Post by **Dave Clark** » Fri Feb 28, 2003 2:25 pm

George
Any tips on how to support the tail in a way that you don't have to jack it up at each heading change? It usually takes me at least twice around the rose to get it swung so that's about eight jackings.

The International Cessna 170 Association

compass placement

compass placement

compass location