Compass help needed

[Nukemzzz]

Long story short...my whisky compass deviation was too high and the compensation wasn’t strong enough to correct it. Changed to a new vertical card compass with balance balls and it’s close, but still not legal in the NW quadrant. Yesterday I tried moving it to a different position with no luck. 

I really could use some help locating a growler or some advice on how to shield it from the center and top tubes. Has anyone had any luck with shielding?

Side note : I’m aware of all the prior forum topics on this. What I need is some help addressing the issue. My A&P and avionics guys don’t seem interested in helping on this one since a compass isn’t really used anymore. But I have a check ride coming for my ppl. Can’t go without a working compass. I need the growler tool or someone raising their hand saying that wrapping a foil around the center tube worked or something. 

[BrianWilkins]

I've used 3 sheets of this shielding under the top of my dash.  That, along with the balls, got me close.  Still not as close as I'd like to be though.  

https://www.aircraftspruce.com/catalog/inpages/magneticcompassshield.php?clickkey=12374

 

 

[carusoam]

https://mooneyspace.com/search/?q=Degaussing&quick=1
 

Have a quick look through these...

The key word is degaussing...

The growler I believe is the tool for this act...

PP thoughts only, not a mechanic ...

-a-

[Raymond J1]

See SB M20 150 A (auxilliary buss bar wire for C, D, E & F).

[GeeBee]

Vertical card compass and truss structures do not mix well. You can de-gauss it but it is short term fix. SuperCub owners know this well. Get a SIRS compass with 4 compensation magnets and never look back.

They come in panel and post mounts

https://www.aircraftspruce.com/catalog/inpages/sirs_compass2.php

 

[BrianWilkins]

3 hours ago, GeeBee said:

Vertical card compass and truss structures do not mix well. You can de-gauss it but it is short term fix. SuperCub owners know this well. Get a SIRS compass with 4 compensation magnets and never look back.

They come in panel and post mounts

https://www.aircraftspruce.com/catalog/inpages/sirs_compass2.php

 

I'd like to hear more about this.  When you refer to the 4 magnets, are you talking about the 4 magnets that are already within the unit, or adding 4 additional magnets?  Why do these work better than vertical card compasses?  Thanks!

[orionflt]

I have a degaussing tool, I have used it on several mooney's including mine when I first got it. it does seem to make a difference on the wet compass but I'm not sure how often it needs to be done. I installed the SIRS compass in my Mooney and haven't had to degauss mine since, not sure if its because I changed out most of my old avionics or the SIRS is less affected.

Brian

[GeeBee]

39 minutes ago, BrianWilkins said:

I'd like to hear more about this.  When you refer to the 4 magnets, are you talking about the 4 magnets that are already within the unit, or adding 4 additional magnets?  Why do these work better than vertical card compasses?  Thanks!

A normal compass such as Airguide or the vertical compass has two magnets that adjust to compensate for deviation. The SIRS has 4 so you have to move each magnet less and the "loop" of deviation is smaller throughout the range. So when you swing it after installation, you cut the process in half. It also uses silicon fluid rather than alcohol so it dampens better. The diaphragm is made of brass, so it does not leak. Standard equipment in Airbus.

When I installed one in my PA-18, I had it "dialed in" 5 minutes. 

 

[DXB]

On 4/1/2021 at 10:21 AM, Nukemzzz said:

Long story short...my whisky compass deviation was too high and the compensation wasn’t strong enough to correct it. Changed to a new vertical card compass with balance balls and it’s close, but still not legal in the NW quadrant. Yesterday I tried moving it to a different position with no luck. 

I really could use some help locating a growler or some advice on how to shield it from the center and top tubes. Has anyone had any luck with shielding?

Side note : I’m aware of all the prior forum topics on this. What I need is some help addressing the issue. My A&P and avionics guys don’t seem interested in helping on this one since a compass isn’t really used anymore. But I have a check ride coming for my ppl. Can’t go without a working compass. I need the growler tool or someone raising their hand saying that wrapping a foil around the center tube worked or something. 

I’ve tried shielding - zero luck.  In my case it required degaussing both the front of the steel cage AND the engine mount. And vertical cards are more finicky than whiskey compasses in this regard. Make sure your compass is far away outside the plane when degaussing.  

[Nukemzzz]

9 hours ago, DXB said:

I’ve tried shielding - zero luck.  In my case it required degaussing both the front of the steel cage AND the engine mount. And vertical cards are more finicky than whiskey compasses in this regard. Make sure your compass is far away outside the plane when degaussing.  

I ordered a CRT TV degaussing coil off eBay today hoping I can demag this thing. 

[carusoam]

Degaussing properly should get things working well enough...

Avoiding large magnets being brought into the airframe will help things from getting worse again...

Leave the big old industrial vacuum cleaner motor far away from the plane... 

Best regards,

-a-

[DXB]

13 hours ago, Nukemzzz said:

I ordered a CRT TV degaussing coil off eBay today hoping I can demag this thing. 

Yeah your situation has many parallels to my previous one - it was a real PITA - I ended up using a TV coil as well.  The coil had to be put in series with a light bulb socket with a 660W cone heater element in it  (https://www.lightbulbdepot.com/products/details/di/660w-120-volt-cone-heater-heat-element-not-bulb/29036a/) to provide enough current to degauss adequately. Burning / electrocuting yourself then becomes a real possibility, and it's ideally a two man job. Here's the thread I made at the time in case it's useful.

 

Edited April 3, 2021 by DXB

[gsxrpilot]

Personally, I wouldn't care if my compass was 180° off. I'd just mark the card and forget about it. It's got to be the most useless instrument in the cockpit. With all the possible navigation equipment available today, it's a relic, even if a required relic.

*rant off*

[Hank]

1 hour ago, gsxrpilot said:

Personally, I wouldn't care if my compass was 180° off. I'd just mark the card and forget about it. It's got to be the most useless instrument in the cockpit. With all the possible navigation equipment available today, it's a relic, even if a required relic.

*rant off*

As long as your fancy electronics still have power to function, and you can get somewhere VFR before their internal batteries run down. Some are 30 minutes when new, wonder what their capacity is after 6-8 years?

[McMooney]

1 hour ago, gsxrpilot said:

Personally, I wouldn't care if my compass was 180° off. I'd just mark the card and forget about it. It's got to be the most useless instrument in the cockpit. With all the possible navigation equipment available today, it's a relic, even if a required relic.

*rant off*

have to agree, long as it's known/consistent wouldn't really matter.  

[Nukemzzz]

All good points and I agree.  However, as I said above, I have my PPL check ride coming and having the NW quadrant out by 23deg is a good way to fail the check ride.  It’s my understanding just asking: “are you ok with testing me with a compass that is above spec for deviation” would be an automatic fail. 

[gsxrpilot]

7 minutes ago, Nukemzzz said:

However, as I said above, I have my PPL check ride coming

Sorry I missed that part. Yeah, you'll need a compass that's a little more accurate.

[EricJ]

Could just borrow one temporarily or something.   It doesn't take long to swing a compass and make a new card for it.   I'd then make sure to point out to the DPE that you went through the trouble to do all that since you knew it would be an issue.   

[DXB]

17 hours ago, EricJ said:

Could just borrow one temporarily or something.   It doesn't take long to swing a compass and make a new card for it.   I'd then make sure to point out to the DPE that you went through the trouble to do all that since you knew it would be an issue.   

It's not a bad idea - a whiskey compass is more likely to be compensated than a vertical card - however that swap didn't work for me, and i still had to go through the ordeal of degaussing.  In the end I didn't even get asked to do compass turns on my IFR checkride; had I known I wouldn't hav bothered with the hassle  

[Yetti]

On 4/3/2021 at 6:26 PM, gsxrpilot said:

Personally, I wouldn't care if my compass was 180° off. I'd just mark the card and forget about it. It's got to be the most useless instrument in the cockpit. With all the possible navigation equipment available today, it's a relic, even if a required relic.

*rant off*

I carry one of these as a back up to the vertical card compass which is spot on. and handheld back up GPS which is a back up to the phone which is a back up to the tablet.  Which is a back up to the D10A which is a back up to the Skyview.   It theory I may have to find a road while on foot.

[Nukemzzz]

Update...

I pulled the the plane out on the apron and faced it East, took note of the compensated compass reading, removed the compass, then used the tool pictured below to degauss per the service bulletin. When I re-installed the compass it was reading 10 degrees different and this is in the East direction which was low deviation (N-W was the maim issue).  So it seemed to have a big impact!   I need to re swing the compass now and see how much it helped. 

[GeeBee]

To meet the original certification requirements the FAA considers more than 10 degrees deviation excessive (FAR 23.1327). If you cannot hold to that you must placard per 23.1547. You may say, yes, but this is CAR 3. However AC43.13 basically says the same thing. 10 degrees. So an installation exceeding that is not considered conformal to AC 43.13. Do you really want to explain a non conforming installation?

[Nukemzzz]

14 hours ago, GeeBee said:

To meet the original certification requirements the FAA considers more than 10 degrees deviation excessive (FAR 23.1327). If you cannot hold to that you must placard per 23.1547. You may say, yes, but this is CAR 3. However AC43.13 basically says the same thing. 10 degrees. So an installation exceeding that is not considered conformal to AC 43.13. Do you really want to explain a non conforming installation?

Have you read my posts?  The whole reason I'm working on this is to get it within the 10 degrees.  You are preaching to the choir.

[Nukemzzz]

On 4/3/2021 at 11:25 AM, DXB said:

Yeah your situation has many parallels to my previous one - it was a real PITA - I ended up using a TV coil as well.  The coil had to be put in series with a light bulb socket with a 660W cone heater element in it  (https://www.lightbulbdepot.com/products/details/di/660w-120-volt-cone-heater-heat-element-not-bulb/29036a/) to provide enough current to degauss adequately. Burning / electrocuting yourself then becomes a real possibility, and it's ideally a two man job. Here's the thread I made at the time in case it's useful.

 

 

The cone heater addition thing is confusing me.  Adding something in series will reduce the current, not increase it, because it can only increase the resistance (Well...unless you inserted a capacitor but lets not get crazy!).  I=V/R  (Voltage is fixed). 

I just took the degauss coil and used it as-is.  It could only be ran for 30 minutes because it would overheat if ran longer.   This is evidence that the amperage, going through the coil, is already as high as you can go without damaging things.  I could smell the plastic getting hot inside after about 15 minutes of use.

 

 

[GeeBee]

57 minutes ago, Nukemzzz said:

Have you read my posts?  The whole reason I'm working on this is to get it within the 10 degrees.  You are preaching to the choir.

My response was to those above who say as long as it is "on the card" it is "ok". What you are doing is good work, but I have to tell you de-gaussing is a short term fix. Too much current flows through the frame for it to hold.