Raptor05121

IFR & Mooney Mag Compasses

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So its no surprise my cage is magnetized. I had the old whiskey compass which was no good. Upgraded to a PAI-700 simply to help with my IFR training and added the compensating balls, but on E/W cardinal directions, its 16-18 degrees off, and N/S is about 5-7 degrees off.

I don't have an "onboard" GPS. I'm /A with 6-pack, dual VOR and DME. Realistically and FAA-legally speaking, how do I keep my DG aligned during an IFR flight? I have an EFB, but my CFI says its only showing true course, not heading. Its obviously A LOT more accurate than 15 degrees off mag heading, but is it legal if a DPE were to see me update it?

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Given that, the generally accepted legal limit is 10deg., it would put you in an awkward situation doing compass work.  If the correction card shows more than 10...than it technically needs fixing.  Really depends on the examiners attention to detail if he will question it.  I would get it fixed so you are not stacking the odds against yourself before you even start the exam.  @DXB had a recent thread with lots of Tshooting advice.  In the end, he was able to correct it by degaussing.  

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I wouldn’t correct the DG off an EFB, especially in front of a DPE.  Does the DG really change that much during a short flight like a check ride?

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So its no surprise my cage is magnetized. I had the old whiskey compass which was no good. Upgraded to a PAI-700 simply to help with my IFR training and added the compensating balls, but on E/W cardinal directions, its 16-18 degrees off, and N/S is about 5-7 degrees off.

I don't have an "onboard" GPS. I'm /A with 6-pack, dual VOR and DME. Realistically and FAA-legally speaking, how do I keep my DG aligned during an IFR flight? I have an EFB, but my CFI says its only showing true course, not heading. Its obviously A LOT more accurate than 15 degrees off mag heading, but is it legal if a DPE were to see me update it?


Reach out to Lance Keve. Lance just went through this nightmare and finally was able to get the compass swung. He can tell you what he did.


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A few comments, some of which are tentative and controversial:

-Compass installs must be calibrated to within 10 degrees on all headings and signed off by an A&P.  

-However, I'm not entirely clear that a compass is even required for IFR flight - no mention in required equipment except needing all the vfr required equipment.  The vfr required equipment includes a "magnetic heading indicator"  - so my magnetometer would seem to qualify and negate the need for a compass. A gyro DG however would not.

-Despite not clearly being required for IFR flight, the IFR ACS testing manual makes reference to compass turns, which is why I went to all the trouble to degauss my airframe and practice them before my checkride.  See description of PITA here: 

 

-However I never had to do compass turns on my test so I would have been fine skipping the ordeal. My instructor seemed to think there was a real chance of needing it accurate though.

-Without a panel certified GPS and/or magnetometer, you'd be much more likely to need the compass in a partial panel situation on the test or real life, so it's probably worth it to get your compass working.  

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Panel gps doesnt help as that would only show track not heading that is required to fly atc vectors. It’s why the g5 must have a magatometer to be a dg. 

-Robert 

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So where would one find a degaussing station?

 

Ask Lance Keve. He has one. He is in the same place as you, working on his instrument rating and his compass couldn’t be swung. You should compare notes.

 

 

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However if a GPS has air data a magnetic course can be inferred from track and wind correction angle to back-calculate magnetic heading.

Similarly a handheld GPS without air data will back calculate magnetic track regardless of wind correction angle; that is why your handheld can show deg-M on the data label. 

It makes more sense to have airplanes fly a track than a course when flying to geographically defined waypoints or receiving radar vectors, but the FAA hasn't evolved to the age of magenta.  Currently the controller has to have some sort of idea of winds aloft and tells you to fly a magnetic course of "XYZ".  He/she then has to either know that you have a wind out of whatever direction and compensate for that up front with the instruction, or you get one or two more "turn additional 5-10 deg to the left" to adjust the vector for whatever track they are observing vs what they expected.  Not very efficient.

Flying in the NE corridor I eventually tired of the massaged vectors and started flying my magnetic track off the GPS when it was legally  "close enough" to the controller's instruction... and I stopped getting the additional instructions.  What works in real life doesn't necessarily work on a checkride.

If you and your instructor know about the compass probably have to do something about it.  If I was none the wiser and my DPE/instructor were similarly ill informed, I'd probably just let it go.

YMMV.

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However if a GPS has air data a magnetic course can be inferred from track and wind correction angle to back-calculate magnetic heading.
Similarly a handheld GPS without air data will back calculate magnetic track regardless of wind correction angle; that is why your handheld can show deg-M on the data label. 
It makes more sense to have airplanes fly a track than a course when flying to geographically defined waypoints or receiving radar vectors, but the FAA hasn't evolved to the age of magenta.  Currently the controller has to have some sort of idea of winds aloft and tells you to fly a magnetic course of "XYZ".  He/she then has to either know that you have a wind out of whatever direction and compensate for that up front with the instruction, or you get one or two more "turn additional 5-10 deg to the left" to adjust the vector for whatever track they are observing vs what they expected.  Not very efficient.
Flying in the NE corridor I eventually tired of the massaged vectors and started flying my magnetic track off the GPS when it was legally  "close enough" to the controller's instruction... and I stopped getting the additional instructions.  What works in real life doesn't necessarily work on a checkride.
If you and your instructor know about the compass probably have to do something about it.  If I was none the wiser and my DPE/instructor were similarly ill informed, I'd probably just let it go.
YMMV.


Does the magnetic course a GPS display factor in the magnetic variation?


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1 minute ago, Marauder said:

 


Does the magnetic course a GPS display factor in the magnetic variation?


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Yes it knows your geographic location based on GPS and factors in the EW var

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The compass might be required but when is it actually used other than to set your DG? If you're GPS equipped your going to fly what ever heading it takes to keep on track, VOR/LOC/GS you're going to fly what ever heading it takes to keep the CDI centered,, With vectors ATC will assign a new heading if it's not working out on radar and NO GYRO approaches, ATC starts and stops your turns.

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Hi Alex,

As Marauder has stated, I just went though this fun.  Apologies, long:

Approaching checkride, the only thing still to contend with was my wet compass being way off on a lot of headings, and freezing throughout all turns until the turn was stopped.  I figured it might be the compass itself and since I was down to replacing, I thought I'd give the PAI-700 a try, despite hearing about a 50/50 success rate and some folks liking them and others not.  I was completely aware of the potential frame magnetism issues so purchased the compensating balls, assuming I'd need them and they'd be sufficient to overcome any rogue fields.

I was informed by Precision that the compass replacement and swinging could be done by myself with just a log book entry, however, since I had an appointment with an avionics shop already, I decided to have them do it.  They replaced it fine, however, when we went out back to an open area to swing with someone holding a reverse handheld compass out in front (not too close) of the plane, it seemed the headings were way off.  Almost to the point where trying to adjust would be pointless.  Here's where a potential mistake was made.  Instead of trying to at least get as close a possible, after going around in a few circles, we went back to the hangar and installed the compensating balls.  Precision states that you should at least try to adjust with internal compensators as close as possible before using the external compensating balls.  Unfortunately, we could not reach their tech support that day due to FAA inspector meetings they had.

So, back out to the open area and round and round with the hopes that the compensating balls would do the trick.  It was hopeful for the first half as deviations were looking less than 10 degrees and some spot on.  But, from 270 on to 330, they were way off.  22 degrees was the worst.  Fail.  Crazy part is we finally got a hold of Precision but it was too late in the day.  Without telling them where our deviations were they said they'd bet it was the W to N quadrant.  Yes it was.  

We spoke about the magnetism and degaussing, however, they didn't have a tool and nobody I called (other avionics shops) did either.

So, giving up on that, I left deflated and needed to think about the possibilities.

I didn't get clearance on the home front to rip the coil out of an old, but perfectly working, TV so in desperation, bought a degaussing coil: GC Waldom Degaussing Coil, 9317 (Available at a lot of online electronics outlets)

Right or wrong, this is how I approached it.  (Note: There may have been some voodoo involved)

Took the VCC out and removed the compensating balls.  Reset the internal compensating screws to align with how they came from Precision.  Moved the compass around (with power off) the panel area and up/down to see what kind of movement was prevalent in what areas and if there were any trends. It was shocking how much it moved by just dropping it an inch or two and from side to side.  Swung slightly when moving up/down center post but also moved when along roof line to side frame member by windshield.  More so on the right than the left.  Conclusion:  It's all wacky

Removed the VCC from the cockpit and put it far away for the degaussing process.  Ran some heavy extension cords and draped it over a fat pillow going in through the baggage compartment door (SB M20-150A, 04-22-68 - States keeping cord at least 6 inches away from frame members).  As per that SB, had both seats back all the way, started with coil low (and off), turned it on and moved to low front center, then up j-bar and center stack and on to center post.  Then circled around towards me, back down and up again, this time moving to right and across to top outer frame sides and quickly repeated for left side.  They advise circular motions while doing, which I did.  Had to move relatively quickly but not hastily, as the coil instructions state to not use continuous for more than 60 seconds due to overheating.  Then wait 30 minutes for cooling to attempt again.  They weren't kidding, I'm sure I hit the minute mark and that coil was nearly scalding in my hand.  So, when I completed the process, I quickly (with button still depressed) exited the cabin and held it far away while releasing the button.

Did it do anything?...

I brought the VCC back into the cabin and repeated the process of moving it around and checking for how much movement.  It wasn't quite scientific as I didn't record, either before or after, specific spots and deviation swings.  It still moved, but potentially less in some areas.

Did I mention it was in the 90's with high humidity?  With that, I wasn't in the mood to wait 30 minutes to try some more.  Packed up and decided to fly over to the avionics shop and see if they'd help swing again, starting without compensating balls and go from there.  Short version:  They had plenty of time to talk about it but not enough time to go out and do it.  I was informed of a compass rose at another airport 30 miles West so figured I'd give it a shot.

Brass adjusting screwdriver in hand, set off and aligned on N.  It was a bit off, so adjusted.  Went to E.  It was a bit off, so adjusted.  S, what?!?, right on.  W, 266!, I'll take it.  Then went to all 30 degree intervals and shockingly found most to be very close with the worst deviation being 7 and 8 degrees.  Again, this is with the native internal compensating screws and the external balls not installed.  Did the voodoo work?  Not really sure.  A lot of things in the chain make me wonder.  Accuracy of the handheld compass method, trying with compensating balls before getting close without,  compass rose method, etc.

Although that SB should have been done in '68, and a lot of it talks about the wiring going back to battery and not to frame members, it wouldn't surprise me if shops along the way have done installs and not known about that and have grounded lights, etc., to the nearest frame member, adding to the magnetism issue.  It's clear that when I turn my strobes on, the compass moves a good amount in one direction.  Then if I add my beacon, it moves the same amount further in the same direction.  Pitot heat didn't help either.  The other electrics didn't seem to have any affect.  And here's an oddity.  In flight tests on the way home, turning the strobes on or off on a particular heading, didn't move the compass at all!?  

So, here's where I am.  Got it in spec, however that happened.  Can feel confident that it is accurate enough to use as a backup.  Know that I can pop over to that compass rose for periodic sanity checks  and redo if necessary.  And will keep that degaussing coil handy as I'm sure (most folks have said, including Precision) the magnetism will reintroduce itself over time.  Perhaps I'll make it a periodic thing and chip away at degaussing more and even the engine mount/frame area.  Rewiring the entire plane, with special attention to grounding may help but I'm not up for that at this time.  Always a battle.

Hope that helps and doesn't discourage too much.  I think I got lucky as I've heard of others doing a far more intensive degaussing process.

Regards,

Lance

ps, just added the SB attachment

 

 

 

sbm20-150a.pdf

Edited by Lance Keve
Adding attachment
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Hi Alex,
As Marauder has stated, I just went though this fun.  Apologies, long:
Approaching checkride, the only thing still to contend with was my wet compass being way off on a lot of headings, and freezing throughout all turns until the turn was stopped.  I figured it might be the compass itself and since I was down to replacing, I thought I'd give the PAI-700 a try, despite hearing about a 50/50 success rate and some folks liking them and others not.  I was completely aware of the potential frame magnetism issues so purchased the compensating balls, assuming I'd need them and they'd be sufficient to overcome any rogue fields.
I was informed by Precision that the compass replacement and swinging could be done by myself with just a log book entry, however, since I had an appointment with an avionics shop already, I decided to have them do it.  They replaced it fine, however, when we went out back to an open area to swing with someone holding a reverse handheld compass out in front (not too close) of the plane, it seemed the headings were way off.  Almost to the point where trying to adjust would be pointless.  Here's where a potential mistake was made.  Instead of trying to at least get as close a possible, after going around in a few circles, we went back to the hangar and installed the compensating balls.  Precision states that you should at least try to adjust with internal compensators as close as possible before using the external compensating balls.  Unfortunately, we could not reach their tech support that day due to FAA inspector meetings they had.
So, back out to the open area and round and round with the hopes that the compensating balls would do the trick.  It was hopeful for the first half as deviations were looking less than 10 degrees and some spot on.  But, from 270 on to 330, they were way off.  22 degrees was the worst.  Fail.  Crazy part is we finally got a hold of Precision but it was too late in the day.  Without telling them where our deviations were they said they'd bet it was the W to N quadrant.  Yes it was.  
We spoke about the magnetism and degaussing, however, they didn't have a tool and nobody I called (other avionics shops) did either.
So, giving up on that, I left deflated and needed to think about the possibilities.
I didn't get clearance on the home front to rip the coil out of an old, but perfectly working, TV so in desperation, bought a degaussing coil: GC Waldom Degaussing Coil, 9317 (Available at a lot of online electronics outlets)
Right or wrong, this is how I approached it.  (Note: There may have been some voodoo involved)
Took the VCC out and removed the compensating balls.  Reset the internal compensating screws to align with how they came from Precision.  Moved the compass around (with power off) the panel area and up/down to see what kind of movement was prevalent in what areas and if there were any trends. It was shocking how much it moved by just dropping it an inch or two and from side to side.  Swung slightly when moving up/down center post but also moved when along roof line to side frame member by windshield.  More so on the right than the left.  Conclusion:  It's all wacky
Removed the VCC from the cockpit and put it far away for the degaussing process.  Ran some heavy extension cords and draped it over a fat pillow going in through the baggage compartment door (SB M20-150A, 04-22-68 - States keeping cord at least 6 inches away from frame members).  As per that SB, had both seats back all the way, started with coil low (and off), turned it on and moved to low front center, then up j-bar and center stack and on to center post.  Then circled around towards me, back down and up again, this time moving to right and across to top outer frame sides and quickly repeated for left side.  They advise circular motions while doing, which I did.  Had to move relatively quickly but not hastily, as the coil instructions state to not use continuous for more than 60 seconds due to overheating.  Then wait 30 minutes for cooling to attempt again.  They weren't kidding, I'm sure I hit the minute mark and that coil was nearly scalding in my hand.  So, when I completed the process, I quickly (with button still depressed) exited the cabin and held it far away while releasing the button.
Did it do anything?...
I brought the VCC back into the cabin and repeated the process of moving it around and checking for how much movement.  It wasn't quite scientific as I didn't record, either before or after, specific spots and deviation swings.  It still moved, but potentially less in some areas.
Did I mention it was in the 90's with high humidity?  With that, I wasn't in the mood to wait 30 minutes to try some more.  Packed up and decided to fly over to the avionics shop and see if they'd help swing again, starting without compensating balls and go from there.  Short version:  They had plenty of time to talk about it but not enough time to go out and do it.  I was informed of a compass rose at another airport 30 miles West so figured I'd give it a shot.
Brass adjusting screwdriver in hand, set off and aligned on N.  It was a bit off, so adjusted.  Went to E.  It was a bit off, so adjusted.  S, what?!?, right on.  W, 266!, I'll take it.  Then went to all 30 degree intervals and shockingly found most to be very close with the worst deviation being 7 and 8 degrees.  Again, this is with the native internal compensating screws and the external balls not installed.  Did the voodoo work?  Not really sure.  A lot of things in the chain make me wonder.  Accuracy of the handheld compass method, trying with compensating balls before getting close without,  compass rose method, etc.
Although that SB should have been done in '68, and a lot of it talks about the wiring going back to battery and not to frame members, it wouldn't surprise me if shops along the way have done installs and not known about that and have grounded lights, etc., to the nearest frame member, adding to the magnetism issue.  It's clear that when I turn my strobes on, the compass moves a good amount in one direction.  Then if I add my beacon, it moves the same amount further in the same direction.  Pitot heat didn't help either.  The other electrics didn't seem to have any affect.  And here's an oddity.  In flight tests on the way home, turning the strobes on or off on a particular heading, didn't move the compass at all!?  
So, here's where I am.  Got it in spec, however that happened.  Can feel confident that it is accurate enough to use as a backup.  Know that I can pop over to that compass rose for periodic sanity checks  and redo if necessary.  And will keep that degaussing coil handy as I'm sure (most folks have said, including Precision) the magnetism will reintroduce itself over time.  Perhaps I'll make it a periodic thing and chip away at degaussing more and even the engine mount/frame area.  Rewiring the entire plane, with special attention to grounding may help but I'm not up for that at this time.  Always a battle.
Hope that helps and doesn't discourage too much.  I think I got lucky as I've heard of others doing a far more intensive degaussing process.
Regards,
Lance
ps, just added the SB attachment
 
 
 
sbm20-150a.pdf


You forgot to mention that Marauder was doing anti-magnetism chants for you.


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14 minutes ago, Marauder said:

 


You forgot to mention that Marauder was doing anti-magnetism chants for you.


Sent from my iPad using Tapatalk Pro

 

That is true.  And you had to hear (read) my crying and cursing throughout. ;)

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One other thing that was mentioned by Precision, is the use of MU-Metal sheeting for magnetic shielding.  It's available through Aircraft Spruce and I imagine others.  Probably best used when one has identified a specific instrument or avionic that is causing issues for the compass and putting it around that instrument or at least between it and the compass.  I don't think putting it close to the compass would be ideal, though.  Precision did mention using it to wrap the center post but from holding a sheet of it around the post area, I didn't see any difference in compass movement.  I did see it a difference when blocking things like the audio panel a bit.

Anyway, just one more potential option/tool.

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Barely 


You mean you have lost the skill to recite “east is least, west is best”? Sacreligious.


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1 hour ago, RLCarter said:

The compass might be required but when is it actually used other than to set your DG? If you're GPS equipped your going to fly what ever heading it takes to keep on track, VOR/LOC/GS you're going to fly what ever heading it takes to keep the CDI centered,, With vectors ATC will assign a new heading if it's not working out on radar and NO GYRO approaches, ATC starts and stops your turns.

It’s still wrong and is why a magnetometer for a legal hsi is required.  It’s very annoying if every time atc gives you a vector your heading is off. 

-Robert, cfii

Edited by RobertGary1

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Compass is a tool to set the DG after that it is not looked at.  When being vectored use track on GPS this may not be right but unless you are dealing with 20+kt winds 90 degrees to your path the track is usually not that far off from the assigned vector.  Just guessing but within 10 degrees.

If you have total electrical failure and no GPS, VOR available and you need the compass for a general heading it will work fine.  First airport you see land and deal with NORDO issue and move on.

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4 hours ago, Raptor05121 said:

So where would one find a degaussing station?

call Drew brown in Edgewater Fl. Absolute aviation LLC. He has one.

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4 hours ago, RobertGary1 said:

It’s still wrong and is why a magnetometer for a legal hsi is required.  It’s very annoying if every time atc gives you a vector your heading is off. 

-Robert, cfii

The real question is why ATC still issues headings vs track. I suppose there are one or 2 planes still in the "system" that are incapable of displaying track. but the same question can apply to altitude..

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21 minutes ago, mike_elliott said:

The real question is why ATC still issues headings vs track. I suppose there are one or 2 planes still in the "system" that is incapable of displaying track. but the same question can apply to altitude..

Yes I can see a future where atc  issues tracks instead. But today I think there are a lot of planes without an ifr gps flying /a or even /u.  That includes some of mine. No way I’d spend money to /g in the Aztec. It’s a great plane but probably barely worth an ifr gps in a trade. Haha 

fly it until something major costs money and then scrap it. That’s the nature of the twin market now. They’re disposable. 

Edited by RobertGary1

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I always found it interesting in primary training that I was supposed to calculate down to the degree which included the wind, which is not constant.   Then apply that to this shaky thing 5 feet away from my head that is only marked off in 5 degree increments.    I mean srysly why even worry about minutes and seconds part of the degrees minutes seconds....

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