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Magnetometer GRU-11 & LED Strobe

mfleming

Well Known Member
Patron
I'm selecting the mounting location for my Garmin GRU-11 magnetometer.

I'm interested in success stories for the aft deck location or wingtip location with LED strobes.

How did this work out for you?

My preference is the aft deck but there's no way to mount back there without violating Garmin's distance rules with electric trim and LED strobes. Wing mound distances are only marginally better.

Any success stories
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Maybe I have to go for for a mid fuselage mount but would rather not.
 
GMU-11

I mounted my GMU-11 on the rear deck below the vertical stabilizer on my RV-6 a number of years ago. I had no issue with calibration, interference, or operation after I got it working. (I had a CANBUS issue on install that was intermittent but once fixed GMU-11 has worked flawlessly.)

I have manual trim with a strobe on top of the vertical stabilizer. Power supply for the strobe is located just aft of the baggage compartment aft bulkhead.

I do not have a photo available but will take one at condition inspection time and post it to my PostImage.org account so that it can be seen here next time someone asks.
 
I have my GMU-11 mounted in the right wing tip in my RV-10, and it works well. I have AeroLED strobes and landing/taxi lights in both wingtips, and there is no interference.

Not sure if this is relevant to your RV-7 install, as the RV-10 has a much larger wing tip which allows for additional distances between the lights as well as the aileron counterweight pipe and the GMU-11. But thought I would offer my success as one data point.

Regards,
 
More Stories Please

Jeez...There must be more installs with led strobes with magnetometers out there.

Lets hear from you :D

How did your magnetometer install work out with LED strobes?

Any problems? What were the fixes if there were?
 
GMU 11 Mounting

Jeez...There must be more installs with led strobes with magnetometers out there.

Lets hear from you :D

How did your magnetometer install work out with LED strobes?

Any problems? What were the fixes if there were?

You may want to consider running a dedicated ground wire for the strobe, rather than grounding it to the airframe out in the wing/in the vicinity of the GMU 11.

You would also want to be mindful of the pitot heat wiring if it is in the same wing. In this case, make sure the wiring for the GMU 11 and the pitot heat wiring are routed in a manner that physically separates them as much as feasibly possible.

Thanks,

Justin
 
You may want to consider running a dedicated ground wire for the strobe, rather than grounding it to the airframe out in the wing/in the vicinity of the GMU 11.

You would also want to be mindful of the pitot heat wiring if it is in the same wing. In this case, make sure the wiring for the GMU 11 and the pitot heat wiring are routed in a manner that physically separates them as much as feasibly possible.

Thanks,

Justin

Thanks Justin,

The AeroLED Strobes use the cable shielding as a ground which runs from the light to the instrument panel ground. The strobe light fixture is grounded locally but it doesn't' carry any current.

I'm really wanting to mount the GMU-11 on the aft deck but I was hoping to get some success stories before I went to the trouble of running the CAN back there.
 
Michael,

Did you end up mounting the GMU-11 on the aft deck?

I'm looking at putting mine in the same place. It doesn't quite meet the 10ft requirement from the auto pilot pitch servo, and not sure about current draw on my tail LED strobe, but I don't think that is an issue.

Were exactly did you end up putting the mount? I assume the deck is going to be close enough to flight level, and I see two possible locations in front of the horizontal stabilizer spar and behind it. Seems like an easy install for the GMU-11 Mount. Just align with centerline, drill 4 holes and rivet.
 
Just me

Thanks Justin,

The AeroLED Strobes use the cable shielding as a ground which runs from the light to the instrument panel ground. The strobe light fixture is grounded locally but it doesn't' carry any current.

I'm really wanting to mount the GMU-11 on the aft deck but I was hoping to get some success stories before I went to the trouble of running the CAN back there.

Although the FlyLED instructions says to use the shield as a ground, i did not. I used a separate ground wire inside the shield per standard practice. I let you know in a year how it works.
 
Led strobes and gmu11

Hi, I have the Whelen Orion650 LED Nav/strobes on my RV8. My gmu 11 is mounted in the left wingtip just aft of the spar. I also have duckworks leading edge landing lights with squadron pro LED landing lights installed.

When I did my magnetometer interference check my highest level of interference was when I turned off my landing lights. 29% of max interference. Check passed.

The led Nav/strobes were not a problem. All of my wires are shielded and grounds go back inboard to a central ground buss.
 
Michael,

Did you end up mounting the GMU-11 on the aft deck?

I'm looking at putting mine in the same place. It doesn't quite meet the 10ft requirement from the auto pilot pitch servo, and not sure about current draw on my tail LED strobe, but I don't think that is an issue.

Were exactly did you end up putting the mount? I assume the deck is going to be close enough to flight level, and I see two possible locations in front of the horizontal stabilizer spar and behind it. Seems like an easy install for the GMU-11 Mount. Just align with centerline, drill 4 holes and rivet.

No, I have not mounted the GMU-11 yet. Warm weather came and I turned my attention to the slider canopy...as soon as I'm done with that I'll return to the avionics and wiring.


Although the FlyLED instructions says to use the shield as a ground, i did not. I used a separate ground wire inside the shield per standard practice. I let you know in a year how it works.


It will be interesting to see how that works.
I spoke with one of the engineers at AEROLED and they had done a lot of testing to come up with scheme of using the shield as a ground.


Hi, I have the Whelen Orion650 LED Nav/strobes on my RV8. My gmu 11 is mounted in the left wingtip just aft of the spar. I also have duckworks leading edge landing lights with squadron pro LED landing lights installed.

When I did my magnetometer interference check my highest level of interference was when I turned off my landing lights. 29% of max interference. Check passed.

The led Nav/strobes were not a problem. All of my wires are shielded and grounds go back inboard to a central ground buss.

My current thinking is using the aft deck or possibly using the VANs mount in the mid-upper fuselage.
 
Hey Mike. I mounted my GMU11 on the aft deck. I'm using a FlyLeds tail strobe and it uses a shielded pair with the ground running back to the control board under the right seat, and eventually to the firewall ground. Also if anyone is interested I have manual trim. I'm not flying yet but I did get the airplane fully assembled a few days ago and did the magnetic interference test followed by calibration and all checked out fine. If I have any problems once in the air I'll report back.

I chose the aft mount based on a) Garmin recommend it, and b) Simplicity. The aft deck is already dead level (or should be ;) so you don't need any fancy mounting bracket.

I joke that when it comes to magnetometers, antennae and fuel flow transducers, if one follows all the rules and recommendations they actually cannot be mounted anywhere on the airplane, but rather somewhere in close formation! Compromise is necessary. At least in this case Garmin do just come out and recommend a location for RV's, which makes it much easier.
 
I have my GMU11 on an aft deck mounted near the top of the second bulkhead behind the baggage bulkhead. AeroLED tail strobe, autopilot pitch servo, power pitch trim, Transponder and remote radio all back there in the same bay, only low to the floor and sidewall.

AeroLEDs use resistors to control the LED current rather than a high frequency drive. This approach wastes a little power as heat, but has no possible emissions that might interfere with audio or radio. Also with LEDs the current draw is small, so induced field strength is small. Just use good practice on running the power wires with separation.

My plane is an RV-10 so, YMMV

No interference at all after 100+ hrs of flight.
 
GMU 11 mount

So I hit the easy button and built a shelve on the aft side of the main cargo panel. Calibration seemed to go well, interference test passed and it's hopefully good to go. I haven't flown yet, only taxiing but this was definitely easy to do.
Btw, I have cables, antenna wire, trim wires, strobe and position light all coming together in the tail hence the decision to not put it there.
Good luck
danny
 
Garmin recommends installation in the wing and, as you noted, installing in the tail won't meet distance requirements from the AP servo.

Mounting on the outboard right wing rib is easy. If you've installed the Almost -14 Mod, the aluminum you cut out of the plane makes a great tray for the GMU-11. Cut about 4 inches out and use it to mount the magnetometer with 3 screws. Just did this in a -7A with AeroLED landing/Nav/Strobes and the interference test easily passed.
 
Garmin recommends installation in the wing and, as you noted, installing in the tail won't meet distance requirements from the AP servo.

Mounting on the outboard right wing rib is easy. If you've installed the Almost -14 Mod, the aluminum you cut out of the plane makes a great tray for the GMU-11. Cut about 4 inches out and use it to mount the magnetometer with 3 screws. Just did this in a -7A with AeroLED landing/Nav/Strobes and the interference test easily passed.

Actually if you reference Appendix B as noted in the installation guide. https://static.garmin.com/pumac/190-01115-01_am.pdf

It states;
'B.2.1 RV-7/9
The typical GMU magnetometer mounting location in RV-7/9 aircraft is in the aft fuselage, on the aft deck (F-714), just ahead of the horizontal stabilizer and just aft of the F-709 bulkhead. This location provides a level pitch and roll reference, and acceptable separation from excessive magnetic disturbances in typical RV-7/9 aircraft'
 
Actually if you reference Appendix B as noted in the installation guide. https://static.garmin.com/pumac/190-01115-01_am.pdf

It states;
'B.2.1 RV-7/9
The typical GMU magnetometer mounting location in RV-7/9 aircraft is in the aft fuselage, on the aft deck (F-714), just ahead of the horizontal stabilizer and just aft of the F-709 bulkhead. This location provides a level pitch and roll reference, and acceptable separation from excessive magnetic disturbances in typical RV-7/9 aircraft'

:confused::p:rolleyes:

How the *#$@ did I miss that :eek:

Thanks

Edit: That passage is for the GMU-22 , apparently thats how I missed it. Hopefully it will apply to the GMU-11
 
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I bought the GMU-11 aft deck mount from Stein Air and mounted it over the right lighting hole. I was worried about plug clearance for the plug from the F-709 bulkhead so I mounted toward the back of the hole.
I saw someone else mounted it closer so that the plug can be accessed through the lighting hole in the bulkhead.
If I were to do it again I would consider making my own mounting plate and possibly using nut plates instead of possibly having to play wrist yoga trying to get nuts and screws in place, but then again once mounted how often will you have to do maintenance on the GMU-11.
I can share a picture through email of what I did if you shoot me an email


[email protected]
 
Previously posted that my GMU-11 was on the aft deck of my RV-6.

Here are a few photos.

2020-07-04 10.16.22.2170.jpg

2020-07-04 10.15.48.3530.jpg

2020-07-04 10.16.02.5730.jpg

Has worked great for the past 3 or 4 years.
 
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