GMU 11 Magnetometer Occasionally Failing

thesmug

thesmug

Pre-Flight
Joined
Jun 2, 2022
Messages
47
Location
Chicago
Display Name
Display name:
thesmug
During a 3 hour cross country, the magnetic heading on both of my dual G5s would occasionally oscillate back and forth a few degrees then completely fail, only to come back a few minutes later. This happened probably 4 times. Does anyone know what the cause could be and if it would be possible to fix without needing to go to an avionics shop?
Additionally, does anyone know what kind of magnetometer it is? My guess is a fluxgate but it would be interesting to know for sure.
 
“Unlike conventional flux valve systems, which detect only the horizontal component of the Earth’s magnetic field, the GMU 11 magnetometer provides full 3-axis vector measurements for the most precise digital indication of magnetic field strength and direction.”
 
Clip4 said:
“Unlike conventional flux valve systems, which detect only the horizontal component of the Earth’s magnetic field, the GMU 11 magnetometer provides full 3-axis vector measurements for the most precise digital indication of magnetic field strength and direction.”
Click to expand...
Yeah, that’s what was unclear to me. It could be a three axis fluxgate but it could also be saying that it’s an entirely different type of magnetometer, depending on how you interpret that sentence.
 
Where is it located on your plane?
Have the G5s been updated ?
Change to any led lights lately?
 
Last edited:
Gary Ward said:
Where is it located on your plane?
Have the G5s been updated ?
Change to any led lights lately?
Click to expand...
Just bought the plane, and the seller doesn’t know where it is but says either the wing or the tail which isn’t really helpful. The G5s are up to date and nothing new has been installed.
Bell206 said:
First plot your route on a full sectional chart and see if it crosses any known "magnetic anomaly" areas. There usually is a note on the sectional.
Click to expand...
I considered it, but one of the times it happened was very close to my home airport where I know for sure that this doesn’t normally happen.
 
Try turning strobes and nav lights off if it happens again. Often the high voltage on conventional strobes with inadequate shielding can interfere with the magnetometer.
 
Hang 4 said:
Try turning strobes and nav lights off if it happens again. Often the high voltage on conventional strobes with inadequate shielding can interfere with the magnetometer.
Click to expand...
We had the strobes off and sadly can't turn off nav lights because having them on is required to keep the ADS-B working. If that turns out to be the case, is it legal to install extra shielding on the cables? I have quite a bit of electromagnetic shielding sleeve at home.
 
Hang 4 said:
Try turning strobes and nav lights off if it happens again. Often the high voltage on conventional strobes with inadequate shielding can interfere with the magnetometer.
Click to expand...
Sounds like a good excuse to go LED. :)
 
thesmug said:
We had the strobes off and sadly can't turn off nav lights because having them on is required to keep the ADS-B working. If that turns out to be the case, is it legal to install extra shielding on the cables? I have quite a bit of electromagnetic shielding sleeve at home.
Click to expand...

I know you don’t know yet, but it’s likely the GMU11 is in the right wing, just before the wingtip. It (GMU11) may need to be shielded or relocated. Ours was relocated to the tail to solve a magnetic heading issue. Our installer did that free of charge as he did not do the magnetic survey per the STC installation instructions.
 
thesmug said:
Just bought the plane, and the seller doesn’t know where it is but says either the wing or the tail which isn’t really helpful. The G5s are up to date and nothing new has been installed.
Click to expand...
The weight and balance and log entry should pinpoint where it was installed.
 
Last edited:
You must log in or register to reply here.
Back
Top