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Old 09-23-2019, 08:56 AM
Frankster13 Frankster13 is offline
Join Date: Feb 2019
Location: Sausalito CA in Northern CA near wine country
Posts: 38
Default Calibrating Garmin AHRS and Compass

I will be needed to calibrate AHRS, Compass and other items on my RV-14A (SF/Bay Area LVK). Does anyone have any tips and trips to make this easier? My plan is to go with the manual steps but wondering if there are any tricks from the RV community for the aircraft side of things.
Frank Ketcham

Last edited by Frankster13 : 09-23-2019 at 09:01 AM.
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Old 09-23-2019, 09:10 AM
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bkervaski bkervaski is offline
Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 1,525


If your field doesn't have a painted compass rose use some masking tape and a real compass to create your own temporary compass rose.

The manual says to do it under power but if you haven't flown yet you can get it done by having someone sit in the plane while you manually move the plane.

Regardless if under power or someone else in the cockpit make sure they have the right brake engaged so it spins on that wheel without moving in an arc.

It should sync up the first time, if not, make sure you aren't too close to your metal hangar.

If you can't get it zeroed in within a few attempts consider you may have a bad magnetometer, this happened to me, after I drug my airplane around the airport in 98 degree weather for 3 hours trying to find a spot that had less "interference" but when I put the replacement unit in it synced up the very first time with no effort.
RV-14A #140376
N196 (Flying)
2019 Bronze Lindy
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Old 09-23-2019, 09:46 AM
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bhester bhester is offline
Join Date: Jan 2005
Location: Hopkinsville, KY
Posts: 929
Thumbs up EZ process

Get in an open area where you can turn the plane completely around.
Follow the directions - very easy process!
Bobby Hester - Builder/Pilot/A&P
Surfing the web from Hopkinsville, KY
N857BH RV7A XP-O360 - Garmin G3X ADS-B IN/OUT 2020 Compliant
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Dec. 2019 VAF donator - alot better than any magazine subscription
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Old 09-23-2019, 11:11 AM
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g3xpert g3xpert is offline
Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,810

Originally Posted by Frankster13 View Post
I will be needed to calibrate AHRS, Compass and other items on my RV-14A (SF/Bay Area LVK). Does anyone have any tips and trips to make this easier? My plan is to go with the manual steps but wondering if there are any tricks from the RV community for the aircraft side of things.
Hello Frank,

When you level the plane (to wings level cruise attitude) for the ADAHRS pitch/roll offset calibration, make sure you calibrate the GSU 25 and the G5 together (or one after the other) before moving the plane.

Having a field with a compass rose is great because you don't have to worry about finding a magnetically "clean" location. Be aware that it may be very difficult to find a clean location where your magnetometer calibration will pass. For example, anywhere on the ramp where there is concrete with embedded metal (rebar) will probably fail.

At my local airport I tried all over the taxi-ways and ramp areas before finally finding a spot on the edge of a paved run-up pad at the far end of the field that I can reliably pass the magnetometer calibration (every time).

We agree with Brian that it is ok to perform the initial magnetometer calibration with the engine off if that is easier. If you later have heading problems you can repeat the magnetometer calibration at any time without having to re-calibrate the pitch/roll offsets on the GSU 25 and G5 units.

It is not actually necessary to mark off a compass rose, since all you need is to align the aircraft with magnetic north using a handheld compass to start the process. The GDU will tell you where to pause as you turn right 30 degs at each point in the calibration. You don't need markings on the ground or to use the handheld compass after you get started.

It is also not necessary to lock a brake and spin around in a circle. Just taxi or push the plane around as shown in the manual and stop each time the display tells you to and it will be fine.

Garmin G3X Support
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.

Last edited by g3xpert : 09-23-2019 at 11:31 AM.
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Old 10-16-2019, 02:04 PM
DeltaVee47 DeltaVee47 is offline
Join Date: May 2017
Location: Houston, Tx
Posts: 56
Default gmu22

Hi all
I am currently troubleshooting a calibration issue with the G3Xperts but thought I would query the assembled as we are not coming up with a solution as yet.
I have GMU22 mounted on the left wing shelf per the usual RV14.
The unit passes the interference test but when I swing the plane as directed by the system I get a message at completion that says "calibration score 9%". I have tried 4 times in various places including our compass rose and get this exact message each time. I also tried removing all the mounting hardware in case something got magnetized but no luck.
Any other ideas gratefully appreciated as this is holding everything up.
Greg Beckner
N557GB now 5 hours into flight test
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Old 10-16-2019, 04:45 PM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,553

Verify you have the AHRS orientation set correctly.
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
Website:, Email:, Cell: 972-746-5154
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