Century Remote Compass Indicators

[BigTex]

I'm having some real challenges to de-magnetize my airframe and be able to swing my compass within the 10+/- requirements. I'll attempt to install a SIRS compass to see if that works any better for if not, I'm likely looking at a remote indicating compass like the Century F-115. Does anyone have experience with this instrument of something similar?

[JaredDavis]

Hi,

Did a previous owner do any of the M20-8,M20-134 or M20-150A modifications?

Are you using the http://www.mooney.com/images/pdfs/sb-pdf/sbm20-150A.pdf procedures?

Not sure I would want a compass that requires power to work.

Regards

Jared

65C

[carusoam]

Big Tex,

Is the situation you have possibly because the compass is mounted on the metal post?

My experience in the M20C, the post would shadow the compass causing extreme lag when making 360 deg turns. It became obvious during IFR training. It would slow up going through a particular heading, probably N, hang for a second, than accelerate to catch up.

Or do you have a consistent offset?

I recall a discussion on this topic a while ago.

I thought a new compass was needed. It had the same problem.

Mooney's solution was to mount the compass to the top of the instrument panel instead.

Hope this may help.

Best regards,

-a-

[BigTex]

The compass is mounted on the center section between the windshield. When the plane is pointing either east or west, it is off as much as 90 degrees. Not sure mounting the compass off the post will be good enough. The compass starts swinging when I get within a foot for the center post. I also looked at mounting the compass in the instrument panel but just about any place we put the compass will cause it to swing. The compass we're using is a Precision Vertical Card compass. We're picking up a SIRS to see if that style of compass would make any difference.

The prior owner mentioned that SB M20-150A was complied with but after going through the log books I don't see it. I also talked to Mooney and they don't have any record of the compliance card for that SB was mailed back to them. I've asked the Avionics shop doing the work with the compass to validate if it looks like the SB was complied with. If not, doing the work in the SB might be the next step.

[ryoder]

I was transcribing my logbooks to an excel spreadsheet today and found that a Century Remote Compass kit was installed in 1976 about a month after I was born

 

I didn't even know what it was in my airplane.  I thought it might be an old ADF indicator that wasn't hooked up to anything.  I don't even know if it works but I'll try it out next time I fly and report back.

 

You can see it on the right side of the panel in this pic.  

 

http://allaviations.com/N79396%20Mooney/HighRes_WF21B032369645006.jpg

[triple8s]

I had a HELL of a time with the compass, I did my IFR training in rental plane because the CFII wanted me to get the compass issues resolved before we did the training. I checked in to it and found a service bulletin saying the cable feeding the busses should be removed and install a longer supply cable that went across the fuse behind the panel and back to the tie in so as to cancel out its own magnetic field. This was to be done AFTER degaussing and the avionics shop said they would reccomend removing all the instruments or they wouldn't be responsible for any that were damaged during the degaussing. I had to do something so I made a spacer from 1inch square aluminum tubing to space the compass away from the tube. I used brass machine screws, washers and nuts. Closest I could get was 15 deg off with the engine running and all the systems turned on. I also had to have the prop dynamically balanced because of the compass being mounted on the square tube made it more prone to vibration. In retrospect I'd say if I had replaced the cable it would have gotten within the 10 deg with the spacer and the cable replaced and rerouted.

M20-150A

[BigTex]

Yeah... for the pre-201's it can be quite an adventure.  I had the SB done  to re-route cables and degaussing.  Even after that, when I brought in the vertical card compass, its head spun around like something from the Exorcist.  Ultimately resolved the issue by installing a SIRS compass.

[drapo]

I was transcribing my logbooks to an excel spreadsheet today and found that a Century Remote Compass kit was installed in 1976 about a month after I was born

 

I didn't even know what it was in my airplane.  I thought it might be an old ADF indicator that wasn't hooked up to anything.  I don't even know if it works but I'll try it out next time I fly and report back.

 

You can see it on the right side of the panel in this pic.  

 

http://allaviations.com/N79396%20Mooney/HighRes_WF21B032369645006.jpg

I have one just like that, working fine and I use it to double check my SIRS or to set my DG on longer flights.

[Marauder]

Ah, the quest for the working compass. If the underlying cause for the interference isn't corrected, the interference will return. As well, if you do panel changes with a corrected compass, it may be off afterwards.

My issues were caused by avionic wiring run by shops and attaching things directly to the tubing. If you can get the wiring run correctly and don't introduce other magnetism sources to the plane, you can swing any compass and get it to work.

I found on the Precision vertical card that is still needed the compensating balls to get all of the error out. But once I installed the Aspens, it sure is nice having the source being a flux compass. I still keep the old compass verified but it is more window dressing these days.

[N601RX]

What year did Mooney change the center tube from steel to non-magnetic stainless? On my 67 model it is stainless and I've never had any problems with the vertical card attached to it.

[Marauder]

What year did Mooney change the center tube from steel to non-magnetic stainless? On my 67 model it is stainless and I've never had any problems with the vertical card attached to it.

I think the stainless came in when they switch from the square center post to the round one. In my 75, I still had a really tough time getting the compass to stay swung even with the stainless post. Back in the 90s when I was dealing with this, I had one of our EE nerds measure the magnetic fields and it was clear I had a strong magnetic fields created. Almost all of it was eliminated by re-running wires away from the cage and degaussing the plane.

http://www.mooney.com/wp-content/uploads/2014/03/sbm20-150A1.pdf

[carusoam]

888 and I had a similar challenge...

CFII put our IR training on hold because of the compass...

65C behaved as if the tube set up a shadow...interrupting turns based on compass headings.

New compass behaved like the old compass.

I ended up renting a C to complete my training.

Final solution, changed a single letter on the registration. Swapped an R for the letter C.

Hopefully some of the solutions posted here will help somebody out.

Putting off IR training because the compass doesn't work perfectly is a bad idea.

Wish I had MS back then!

Anyone else not getting through IR training because of a sticky compass or other quirky, hard to get past hardware challenge?

Best regards,

-a-