Leaking magnetic compass..

[donshapansky]

I forgot to mention, I now have 25 hrs in my SuperStar 700 and it has the vertical card compass until next Monday when it goes in for some avionics updates and a new SIRS compass!

[Parker_Woodruff]

Nice ride, Don.

[KSMooniac]

Beautiful SuperStar!  Norman Howell (poster here) has an Aerostar in addition to his '77 J.  He likens it to a Twin Mooney.

[donshapansky]

It's hard to wipe the smile off when you turn that thing loose, it will climb at 180 - 190 kias @ 1000'/min but the fuel flows are up there, with intercoolers it is producing 380 hp per side at 45" MAP and 45 gph per side. The good thing is 15 mins to 15 K and then 230 ktas @ 20 gph.

It has been a lot of work to get it to the condition the Rocket is in, not in money so much just chasing details that make it like it was when new. Fortunately I was dealer for these way back and I can lead an A&P to what needs to be done, the Aerostar Owners Assoc is a great resource.

[fantom]

I hate you, Don ;-)

[Parker_Woodruff]

Never updated this thread...

I went with the SIRS compass and like it a lot.  Thanks to those that suggested it, it is a really nice unit.

[Parker_Woodruff]

Never updated this thread...

I went with the SIRS compass and like it a lot.  Thanks to those that suggested it, it is a really nice unit.

[The-sky-captain]

 

Parker- Are you still happy with the SIRS? My original compass sprung a leak last week enroute from FL to LA and I'm in the process of ordering the SIRS Navigator Overhead Compass. Were you able to mount to the center post using the adjustable bracket sent with the unit?

Quote: Parker_Woodruff

Never updated this thread...

I went with the SIRS compass and like it a lot. Thanks to those that suggested it, it is a really nice unit.

 

 

[donshapansky]

Mine is mounted to the center post, and it has to pivot up when the glarshield is removed, be sure you don't misplace the little red plastic thingie, it is used to swing the compass. I have 850 hrs plus with it now and it is a great piece!

[Jerry 5TJ]

My compass started leaking at altitude.  Slow but steady dripping onto the right pantleg was the first symptom.  Pretty soon the liquid level was visible through the glass, too.

The $20 rebuild kit worked fine.   You get to clean a lot of yellowing gunk off the inside of the glass window and off the face of the floating compass card, too, about 47 years worth.  The card is a crisp black and white when you're done, not yellow and gray. 

The whisky compass still swings wildly in turbulence, though; there's a limit to what the gasket kit can fix.   

 

[captainglen]

  A compass leak at high altitude is indicative of an unseen bubble. The diaphram is designed to compensate only for thermal expansion of the fluid. Since fluid it theoretically uncompressable (in reality it is slightly at enormous pressure) altitude has no effect on fluid volume. The airpath compass body and backplate have no ridge and groove to assist the seal of the diaphram with only four small screws to hold it in place. An air bubble will expand greatly with altitude causing the fluid to bypass even a new diaphram.

  I tried the simple submersion and no matter how I turned the compass the last bubble would not come out. In desperation I used a 50cc catheter flush syringe (wife is a nurse) to blow the bubble out with force. It took several attempts with the bubble getting smaller each time but I got it clear and perfect. Point of note, if you do not disturb the compensating magnets a compass swing will not be necessary.

  Since the vertical card compass is really an undampened horizontal compass with a 90 degree gear they are prone to fairly wicked hysteresis. As the gears get dirty the hysteresis gets worse. Since the card is not floating weightless there is also an inertial mass to overcome which is done, but not adaquately by more powerful magnets than in most wet compass designs. the good news is that most small aircraft have enough vibration to act as a dithering vibrator helping to overcome the friction and card mass. This same vibration also assists your altimiter which is prone to hysteresis but in commercial jets because of low vibration the standby altimeter has an electrical vibrator.

 If your airplane flys too smooth the shortcomings of a vertical compass will be more noticable. This is more likely in twins than in single engine airplanes and jets fly extremely smooth. Quarter inch windshields can reduce some vibration even in single engine aircraft causing hysteresis to be more noticable.

[N201MKTurbo]

Fill the compass with fluid. Put your finger over the hole and gently shake it upside down while looking through the window. Work any bubbles to the top. Use an eye dropper or a spray can straw to do the final fill with a few drops of fluid until the fluid is slightly above the top of the fill port. Gently lower the cap onto the fluid, being careful not to trap any air. Then screw it on. Then shake the compass in all attitudes while looking through the window to verify there are no bubbles.

[RJBrown]

Sometimes those compasses fix themselves

hanger fairies

[Supercop0184]

Reviving a really old thread here - I’m wondering if that SIRS is drilled the same as the whisky compass mount I have In there now that mounts to the center bar. 

[carusoam]

Expect a one for one replacement...

wait for somebody with actual knowledge... 

Best regards,

-a-

[Rusty Pilot]

It looks like I have the same problem - leaking compass during flight.  I noticed a wire feeding the compass which I assume is for lighting.  Can that be removed from the compass end.  It looks like reasonable prices from Aircraft Spruce for new replacement.  My only concern is mounting it to match my existing for my 1974 Mooney C model.  Any additional advice is appreciated.

[Raymond J1]

the other solution, to keep your original Compass, is to order the membrane and then repair. The liquid to put is deodorized petroleum distillate.

https://www.chiefaircraft.com/aircraft/flight-instruments/compass-repair-parts.html

 

 

[EricJ]

4 hours ago, Raymond J said:

the other solution, to keep your original Compass, is to order the membrane and then repair. The liquid to put is deodorized petroleum distillate.

https://www.chiefaircraft.com/aircraft/flight-instruments/compass-repair-parts.html

They're pretty simple devices and the only trick when repairing one is getting the air bubbles out.   There are techniques published here and there on how to do it, your mileage may vary.   The parts are cheap compared to a new compass.

That said, this is one of those weird areas where even an A&P or IA are not authorized to do this repair.   Legally, it should go to an instrument shop.

And that said, too, I bet instrument shops very, very rarely see whiskey compasses as the hangar fairies usually get them done first.

Edited December 29, 2020 by EricJ

[Yetti]

On 12/29/2020 at 6:00 AM, Rusty Pilot said:

It looks like I have the same problem - leaking compass during flight.  I noticed a wire feeding the compass which I assume is for lighting.  Can that be removed from the compass end.  It looks like reasonable prices from Aircraft Spruce for new replacement.  My only concern is mounting it to match my existing for my 1974 Mooney C model.  Any additional advice is appreciated.

Get a vertical card and be done with the broken mounts and silly fluid.

[GeeBee]

I am a huge fan of the SIRS compass. It does not leak because it has a brass bellows rather than rubber. Also easier to swing as it has 4 compensating magnets.