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GMU 11 install issue

miyu1975

Well Known Member
Hello,

I got my gmu 11 magnetometer installed tonight but it failed the interference test. I put the unit in the tail on the shelf and was able isolate the issue. When I turn on the nav and strobes together the test goes to 250% interference. I unplugged the tail nav/strobe and ran the test which passed. So the issue is that tail nav/strobe. It is installed with a shielded cable and grounded on both ends.

Not sure what to do other than move the mag. I could move it to middle of the fuse and place it on the same shelf as my Dynon ahrs unit.
 
I don?t think you should ground the shield at both ends on the strobes. It can cause a loop for static interference. Ground only at the end away from the strobes and re test

Jack
 
Well the first test was as you say. I only had the ground on one end away from the strobe. I then grounded the other end with no better test.


The Aeroleds instructions say to ground both ends.
 
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That's interesting. When I'm upgrading an aircraft to G3X and I see that there is a non LED Nav/tail strobe ( Whelen), I usually warn the owner that we may have to change to an LED tail Nav/ strobe. It's usually the Nav side that causes the interference problem.
I usually use the existing strobe cable for power and ground at the Aeroled Suntail and then the existing Nav power wire for the Nav part of the light. At the strobe power pack I unplug the tail cable, then splice in the black and red tail cable to the power supply power and ground wires. Everything works great and no problems with the interference test. When turning on the Nav light during the test, at most I get 3 to 4 % increase. That is with an unshielded Nav wire!!! Also, I usually use the Aeroled Suntail from Vans. Wish I could help.
 
I think if you review the recommended wiring diagram from AeroLed you will find that they use the shield for the ground return path, not as a "shield" in the usual way. I've installed a number of the GMU22 units in close proximity to both wing tip and suntail wired per the diagram with no issues. Just don't run the wire close to the GMU (at least a foot) and you should be ok.
 
I was looking at the Garmin GMU 11 installation guide (Table 14.4 ? Recommended Distances from Magnetic Disturbances) and was wondering how I was going to mount it 10? from the trim servo motor and pitch AP motor? I guess you aren?t seeing interference from them with the unit mounted in the back of your -7?

I was thinking maybe I would mount it in behind the panel since my gear is aluminum ? but then again, my attach brackets and wear plates are steel and there is an 8.2? minimum distance if they are 1 kg (2.2 lbs.) total ? Hmm, I wonder if that is separate or together? Garmin says installation in the wing is preferred ? but those iron pipe/aileron counter weights are probably heavier than the gear mount hardware??

Confused as to which recommendations are more important than the others?
 
Garmin GMU 11 installation guide (Table 14.4 ? Recommended Distances from Magnetic Disturbances)

Where did you find the installation guide? I have a GMU 11 ready to install, but have not been able to locate install manuals.
 
That Garmin document link has a magnetometer installation consideration pdf in the first row from 2013 that only addresses the GMU 44, not the new GMU 11.

So for the GMU 11 instructions download the full G3X/G3X Touch Installation Manual from March 2017 or later (last row), per Bobby's post.

Jim
 
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Nicely hidden in the G3X manual. Never would have thought to look there. It wasn't in my G5 manual. Thanks
 
GMU 11 Installed

I got my GMU 11 installed and calibrated today. Mounted it facing starboard right behind the point where the front spar of the vertical stabilizer attaches to the fuselage of my 6A. (I have no lights in the tail.) The G5 unit passed the interference test and calibration went fine.

I had to update the software on my G5 from version 2.2 to 3.2 to get the magnetometer configuration option. Also, made a mistake in wiring. I used the diagram in the manual for the test setup instead of the proper diagrams for the installation. The current G5 manual is pretty comprehensive, but at about 150 pages gets a little confusing. Garmin tech support got me straightened out shortly though and their telephone wait times weren't bad. I ended up with 4 wires between the magnetometer and the G5.

Best part is pulling that old compass out, and putting it on the shelf.

John
 
49clipper

So, I can mount it 90 degrees to the centerline of the aircraft? Should it be in parallel with centerline, or is any direction not an issue?
 
I would highly suggest you go to the G5 product page and download the installation manual. You can orient the GMU 11 in many different ways but there's minimums with the respect to roll pitch and yaw. In the setup you tell the system which way the connector is pointing.

Jim
 
GMU11 install.

So I built a shelf on the aft side of the main cargo panel of a -9 and it tested fine. I've taxied it and worked rudder cables, control rods, servos and light loads with no problems. It's a location that's been kinda ignored on vaf but it worked for me.
Anyway, just an idea. Good luck.
danny
 
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