Pre J Model Compass

[ManGar]

Hello everyone, I'm a first time airplane owner and I can't seem to find any posts addressing this problem so I'm sorry if I'm repeating a previously addressed issue.

My A&P told me that my compass can't  be adjusted because of a worn worm screw so I bought a vertical card compass from Aircraft Spruce.  He installed it and then told me that because of the steel roll cage of my 1963 M20C, he can't adjust it.  He said that the only way would be to demagnetize the frame but that it would eventually remagnetize and cause the same problem.  Does anyone know if there is a specific compass that can be used on these steel cage Mooneys or if there is anything else that can be done?  BTW...  Aircraft Spruce will not take the vertical card compass back because it was "installed" so if anyone is looking for a "new" one, I'm willing to let it go for $350 which is less than what I paid for it.  It's a 14V PAI 700 Compass N/H and I'll include the Precision PACMO Mooney center post mounting bracket.

 

Thanks for any help you can offer.

 

[RLCarter]

Your A&P is correct, an Avionics shop should be able to degauss the airframe. There are several threads on MooneySpace on the subject along with work arounds other's has used

[BrianWilkins]

I went through your exact scenario a few months back.  You can use your PAI compass but will need to do a couple of things.  First, Spruce sells sheets of anti-interference material.  You can get two sheets of this and apply it to the underside of the top of your panel.  https://www.aircraftspruce.com/catalog/inpages/magneticcompassshield.php.   Spruce also sells these magnetic "balancing balls" that help offset the problem of steel in your cockpit.  https://www.aircraftspruce.com/catalog/inpages/compensator.php.  When I first installed the PAI compass, mine was reading off by more than 90 degrees, so I was about to give up on it as well.  After using the two above fixes, it works great now and is very reliable.

[BrianWilkins]

In addition to my previous post, I would encourage you to call PAI.  You can literally talk to the company founder on the phone and he's extremely helpful in getting the compass working.  I was so frustrated that I was about to sell mine but his suggestions got me working.  Seems to be a pretty good company.

[ManGar]

 

9 minutes ago, BrianWilkins said:

In addition to my previous post, I would encourage you to call PAI.  You can literally talk to the company founder on the phone and he's extremely helpful in getting the compass working.  I was so frustrated that I was about to sell mine but his suggestions got me working.  Seems to be a pretty good company.

Thanks for the advise.  I forgot to mention that I did have the balancing balls but they didn't help enough.  I think I'm gonna try the magnetic compass shield.  

[ManGar]

49 minutes ago, RLCarter said:

Your A&P is correct, an Avionics shop should be able to degauss the airframe. There are several threads on MooneySpace on the subject along with work arounds other's has used

Do you have any idea how much degaussing typically runs and about how long it lasts?

[BrianWilkins]

Just now, ManGar said:

 

Thanks for the advise.  I forgot to mention that I did have the balancing balls but they didn't help enough.  I think I'm gonna try the magnetic compass shield.  

There is a trick to using the balance balls and the instructions that come with it are not clear.  First, you have to reset the compass adjustment screws to their factory default spots.  Also, make sure that when you look at the bottom of the compass, the small indentation on one of the adjustment screws is facing the back of the compass.  BE CAREFUL.  Those screws strip pretty easily.  Once you've got the adjustment screws back to factory default, then follow the instructions for moving the balance balls to get the compass as close to accurate as possible (find a place away from metal buildings, etc and use the compass app on your phone or something).  Once you have the compass really close to accurate by turning the balls, then use the adjustment screws on the compass to fine tune it.  Also keep in mind that this compass relies on a lot of jiggling around to read accurately, which is why the mount has it hanging somewhat loose.  So you should tap on it A LOT or start the engine and let that vibrate it a lot when you're adjusting.  I know all of this sound like a pain, but once you get it set, it really does work well.

[ManGar]

Just now, BrianWilkins said:

There is a trick to using the balance balls and the instructions that come with it are not clear.  First, you have to reset the compass adjustment screws to their factory default spots.  Also, make sure that when you look at the bottom of the compass, the small indentation on one of the adjustment screws is facing the back of the compass.  BE CAREFUL.  Those screws strip pretty easily.  Once you've got the adjustment screws back to factory default, then follow the instructions for moving the balance balls to get the compass as close to accurate as possible (find a place away from metal buildings, etc and use the compass app on your phone or something).  Once you have the compass really close to accurate by turning the balls, then use the adjustment screws on the compass to fine tune it.  Also keep in mind that this compass relies on a lot of jiggling around to read accurately, which is why the mount has it hanging somewhat loose.  So you should tap on it A LOT or start the engine and let that vibrate it a lot when you're adjusting.  I know all of this sound like a pain, but once you get it set, it really does work well.

Thanks Brian!  I will give it a try, I really would like the vertical card compass to work. 

- Manny

[BrianWilkins]

1 hour ago, ManGar said:

Thanks Brian!  I will give it a try, I really would like the vertical card compass to work. 

- Manny

Just making sure... you do know you're supposed to turn the little balls on the balancing ball thing, right?  You turn one of the balls to adjust the N/S and the other to adjust E/W.

[ManGar]

Just now, BrianWilkins said:

Just making sure... you do know you're supposed to turn the little balls on the balancing ball thing, right?  You turn one of the balls to adjust the N/S and the other to adjust E/W.

Yes sir.  I'm aware of that.  Thank you for asking!

[ManGar]

1 hour ago, BrianWilkins said:

I went through your exact scenario a few months back.  You can use your PAI compass but will need to do a couple of things.  First, Spruce sells sheets of anti-interference material.  You can get two sheets of this and apply it to the underside of the top of your panel.  https://www.aircraftspruce.com/catalog/inpages/magneticcompassshield.php.   Spruce also sells these magnetic "balancing balls" that help offset the problem of steel in your cockpit.  https://www.aircraftspruce.com/catalog/inpages/compensator.php.  When I first installed the PAI compass, mine was reading off by more than 90 degrees, so I was about to give up on it as well.  After using the two above fixes, it works great now and is very reliable.

I've been rereading the post.  Am I understanding this correct?  The magnetic interference is coming from the instrument panel and not the center post where the compass mounts?

[BrianWilkins]

Just now, ManGar said:

I've been rereading the post.  Am I understanding this correct?  The magnetic interference is coming from the instrument panel and not the center post where the compass mounts?

You get it from both.  I actually used a small magnet tool (like you use to pickup nails, etc) in my plane to try to figure out where all of the steel was.  The center post is apparently aluminum but the area on the ceiling at the front of the cabin in mine seemed to have some steel in there.  You also get interference from instruments and radios in the dash.  I also explored degaussing like you described but had several A&P's tell me that it generally doesn't last very long.  You can also use your compass (old one or new one) to just hold and move around your cockpit to try to see where magnetic interference is coming from.  The issue, as described to me by the guy at PAI is that the newer compasses use stronger magnets and are therefore more likely to be susceptible to steel or other interference.  The sheets of absorbing material help to block it and the balancing balls help to offset it.  You can also just take those absorbing sheets from Spruce and use painters tape to move them around your cockpit to see how it affects the compass.  Like I said though, in my case I just taped them to the underside of the top of the dash and it worked like a charm along with the balls.

[ManGar]

Just now, BrianWilkins said:

You get it from both.  I actually used a small magnet tool (like you use to pickup nails, etc) in my plane to try to figure out where all of the steel was.  The center post is apparently aluminum but the area on the ceiling at the front of the cabin in mine seemed to have some steel in there.  You also get interference from instruments and radios in the dash.  I also explored degaussing like you described but had several A&P's tell me that it generally doesn't last very long.  You can also use your compass (old one or new one) to just hold and move around your cockpit to try to see where magnetic interference is coming from.  The issue, as described to me by the guy at PAI is that the newer compasses use stronger magnets and are therefore more likely to be susceptible to steel or other interference.  The sheets of absorbing material help to block it and the balancing balls help to offset it.  You can also just take those absorbing sheets from Spruce and use painters tape to move them around your cockpit to see how it affects the compass.  Like I said though, in my case I just taped them to the underside of the top of the dash and it worked like a charm along with the balls.

Thanks!  I already used a magnet to confirm that the center post is steel.  I'm hoping that the sheets will take care of the interference coming from the panel while the balls will take care of the center post.  Did you have to cut the two sheets and tape them together to cover the entire dash?

[BrianWilkins]

Just now, ManGar said:

Thanks!  I already used a magnet to confirm that the center post is steel.  I'm hoping that the sheets will take care of the interference coming from the panel while the balls will take care of the center post.  Did you have to cut the two sheets and tape them together to cover the entire dash?

The sheets are kind of like a thick aluminum foil sort of thing (but I think they're made of nickel).  You can bend them, cut them, or whatever.  They'd cut easily with plain old scissors.  So if your center post is steel, you could easily cut some of the sheet and wrap the post with it.  You might want to cover it with some sort of covering or paint it to make it look better though.  Two sheets will pretty much cover the entire underside of the bottom of the dash.  I used painters tape initially to make sure they fit ok and did the job and then used strong duct tape to hold them in place once I had them exactly where I wanted them (yeah, I know, not exactly A&P quality work, but then I'm not an A&P).  Oh hey, by the way, be careful handling those sheets.  The edges will cut you up!!  They put a warning sticker on them telling you that, which I totally ignored and got a whole bunch of cuts.  haha.

[ManGar]

1 minute ago, BrianWilkins said:

The sheets are kind of like a thick aluminum foil sort of thing (but I think they're made of nickel).  You can bend them, cut them, or whatever.  They'd cut easily with plain old scissors.  So if your center post is steel, you could easily cut some of the sheet and wrap the post with it.  You might want to cover it with some sort of covering or paint it to make it look better though.  Two sheets will pretty much cover the entire underside of the bottom of the dash.  I used painters tape initially to make sure they fit ok and did the job and then used strong duct tape to hold them in place once I had them exactly where I wanted them (yeah, I know, not exactly A&P quality work, but then I'm not an A&P).  Oh hey, by the way, be careful handling those sheets.  The edges will cut you up!!  They put a warning sticker on them telling you that, which I totally ignored and got a whole bunch of cuts.  haha.

Thanks again!!!  It's all very useful information. I did see the warning when I was checking out the product!!!  

[BrianWilkins]

Just now, ManGar said:

Thanks again!!!  It's all very useful information. I did see the warning when I was checking out the product!!!  

No problem!  I'm glad to be able to help someone with something!  Most of the time it's me getting help from someone else.  haha

Please keep me posted on your progress, and like I said, don't hesitate to call PAI.  The dude that runs the place is really sharp and interesting to talk to.

 

[RLCarter]

2 hours ago, ManGar said:

Do you have any idea how much degaussing typically runs and about how long it lasts?

I do not, if it's not off these might get ya there.  Compass Compensator

[ManGar]

31 minutes ago, RLCarter said:

I do not, if it's not off these might get ya there.  Compass Compensator

Thanks Robert!  I had already tried the compensator balls.  I think I'm going to try the compass shield sheets and compensating balls as soon as I get a chance to deviate from the infamous honey do list. 

[MooneyMitch]

I love MS.

[RLCarter]

44 minutes ago, ManGar said:

Thanks Robert!  I had already tried the compensator balls.  I think I'm going to try the compass shield sheets and compensating balls as soon as I get a chance to deviate from the infamous honey do list. 

The list that has no end....Good luck on that deviation. 

[carusoam]

15 hours ago, ManGar said:

Hello everyone, I'm a first time airplane owner and I can't seem to find any posts addressing this problem so I'm sorry if I'm repeating a previously addressed issue.

My A&P told me that my compass can't  be adjusted because of a worn worm screw so I bought a vertical card compass from Aircraft Spruce.  He installed it and then told me that because of the steel roll cage of my 1963 M20C, he can't adjust it.  He said that the only way would be to demagnetize the frame but that it would eventually remagnetize and cause the same problem.  Does anyone know if there is a specific compass that can be used on these steel cage Mooneys or if there is anything else that can be done?  BTW...  Aircraft Spruce will not take the vertical card compass back because it was "installed" so if anyone is looking for a "new" one, I'm willing to let it go for $350 which is less than what I paid for it.  It's a 14V PAI 700 Compass N/H and I'll include the Precision PACMO Mooney center post mounting bracket.

 

Thanks for any help you can offer.

 

1) Degaussing is a standard practice...

It lasts as long as you don’t bring a vacuum cleaner into the cockpit...

2) The balancing balls have worked for a few MSers

3) I don’t recall anyone going down the list this far to try anything other getting the first two steps worked out...

Magic mats that can block magnetic waves without disrupting the compass.... this should be interesting...

It would help to know what the source of this magnetism is before buying sheets large enough to block the whole cabin...

There are a few people around here that have reported succes with various de-Gaussing techniques and pieces of equipment...

My M20C had the compass hanging from the steal post in the middle... the post acted like a magnetic N shadow...

The compass would hang for a while trip past the shadow, then accelerate to catch up...

There are rules that allow for electronic compasses recently... it may make sense to mount the sensor far enough away from the steel cage... like out in the wing somewhere...
 

Newer Mooneys have SS tubes in the middle... and their compass not very close to it...

Best regards,

-a-

[Ross Taylor]

1 hour ago, carusoam said:

It lasts as long as you don’t bring a vacuum cleaner into the cockpit...

Great...I just did exactly that. Haha!

[MBDiagMan]

I put a card compass in my C and then moved it to my J.  No issues in either plane.  I was prepared to buy the balancing balls both times, but it was unnecessary.  This led me to believe it might be something in the cockpit besides the steel cage that causes some folks to have trouble with the card compass.

Edited June 27, 2020 by MBDiagMan

[Yetti]

some more things to try

https://www.wikihow.com/Degauss-a-Computer-Monitor