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Old 10-21-2019, 11:02 AM
DeltaVee47 DeltaVee47 is offline
Join Date: May 2017
Location: Houston, Tx
Posts: 53
Default Compass calibration

Hi all
I posted this question in another thread but I think it got lost.
Anyway, I have G3X touch system with GMU22 compass in the common setup from SteinAir. Everything is working except that I cannot calibrate the magnetometer. It passes the interference test but when I swing the plane I always get a fail message that says calibration score 9%. I have tried multiple locations on the airport including our compass rose, took out all the mounting hardware in case something was magnetize, consulted with Stein and G3Xpert at Garmin without success.
Any thoughts gratefully accepted
Greg Beckner
N557GB, now 8 hours into flight test
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Old 10-21-2019, 11:23 AM
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bkervaski bkervaski is offline
Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 1,333

Similar situation here. I received a bad GMU-22, it never would calibrate. SteinAir sent me a replacement and it calibrated first attempt.
RV-14A #140376
N196 (Flying)
2019 Bronze Lindy
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Old 10-21-2019, 01:02 PM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,321
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
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RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
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Old 12-01-2019, 07:16 PM
DeltaVee47 DeltaVee47 is offline
Join Date: May 2017
Location: Houston, Tx
Posts: 53
Default Magnetometer

Hello everyone
This an update on my compass calibration problem, still not solved.
So far I have borrowed a friends working gmu22, direct wired the gmu22 to the gsu25, moved the gmu22 to the tailcone and tried multiple places to swing the compass including grass and always get the same message at the end. Calibration 9% failed.
The G3Xperts ( I’ve worked my way through 3 now) are willing to send me a replacement GSU25 to try but doesn’t think it will work. On the other hand he doesn’t have any other recommendations either.
I called Stein who has the right attitude but his guys are stumped too.
For Walt I’ve verified tubes forward, connectors down.
So if any of the amazing builders on this site have ideas I’m all ears. I’m about ready to give Dynon a call
Thanks in advance
Greg Beckner
N557GB now 27 hours into phase 1 and going to need a working panel pretty soon.

Last edited by DeltaVee47 : 12-01-2019 at 07:18 PM.
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Old 12-01-2019, 08:58 PM
Norman CYYJ Norman CYYJ is offline
Join Date: Feb 2005
Location: Victoria B.C.
Posts: 1,222

In the past on other aircraft that a compass could not be swung the plane had to be deguassed.
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Old 12-01-2019, 09:25 PM
JDA_BTR JDA_BTR is offline
Join Date: Dec 2013
Location: Baton Rouge, LA
Posts: 887

Engine running or off? Off and manually swinging plane with a helper watching the screen for stop points will help hit the gates better. Also pull the breaker on everything else in the plane so it’s just the min required items. And on a pad with no rebar if you can find one? I suppose that’s the grass....
Ser 104142, RV-14A
Urologist, AME

Last edited by JDA_BTR : 12-01-2019 at 09:27 PM.
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Old 12-01-2019, 09:37 PM
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emsvitil emsvitil is offline
Join Date: Oct 2019
Location: SoCal
Posts: 91

Really stupid suggestion...............

Rotate the plane the other direction on the compass rose.

(Clockwise if you were going Counter-clockwise or vice-versa)

Who knows.......
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Old 12-01-2019, 10:31 PM
JDA_BTR JDA_BTR is offline
Join Date: Dec 2013
Location: Baton Rouge, LA
Posts: 887

Don't know if it matters. I rotated nose to the left....
Ser 104142, RV-14A
Urologist, AME
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Old 12-02-2019, 04:43 AM
Lancair Super ES Lancair Super ES is offline
Join Date: May 2008
Location: York, PA
Posts: 85
Default Manual shows rotation to right; not sure it matters, but...
Calibration Procedure D: Magnetometer Calibration

Calibration Procedure B must be successfully completed prior to Calibration
Procedure D.
Calibration Procedure D must be carried out at a location that is determined to be free of
magnetic disturbances, such as a compass rose. Attempting to carry out this maneuver on
a typical ramp area will not yield a successful calibration. The accuracy of the ADAHRS
cannot be guaranteed if this calibration is not performed at a magnetically clean location.
Taxi the aircraft to a site that has been determined to be free of magnetic disturbances. Ensure that there
are no nearby magnetic materials on or near the perimeter of the site. If unavoidable, maneuver the aircraft
to keep the magnetometer from passing within twenty feet (6.1 meters) of such objects. Additionally
ensure that vehicles or other aircraft are an adequate distance [forty feet (12.2 meters)] away from the
aircraft under test.
At the site, align the aircraft to a heading of magnetic north (5į). It is best to offset the aircraft position to
the left (west) of the North/South axis to allow turning clockwise around the site as indicated in
Figure 32-5.
Figure 32-5 Aircraft Alignment
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Old 12-02-2019, 06:33 AM
Tom023 Tom023 is offline
Join Date: Jul 2011
Location: Cypress, TX
Posts: 320

Greg, if you are flying off hours and want to stop in at Hooks we can try to calibrate it in the exact spot that worked for me twice. I donít think this is an environmental issue but it may be worth a try.
RV14A #140083
Flying! 8/12/19
2019 Donation
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