Hrs: 3

Installation GMU 11 bracket

After some thoughts about the location of the GMU 11 magnetometer it was time to mount the bracket.

TAF has a new location for the GMU 11, which is behind rib 5. Reason is that if there is luggage containing metal pieces which are stored in the extended baggage compartment it could interfere the magnetometer’s signal. But i don’t like this location since it’s pretty close to the rudder cables and at that location the inspection panel is small.

Here an image of another Sling where you can clearly see that the rudder cables are so close to the bracket that they are even touch the bracket:

Since I’m not installing the extended baggage compartment it fine to install it at the old location. This old location is behind rib 4 and is next to the larger inspection panel. These holes are not punched so I asked TAF for the correct location:

TAF provided small flange aluminum rivnuts. Other builders made a doubler because these rivnuts were not clamping sufficient. I used larger M4 aluminum rivnuts which hold perfectly in the thin bracket. With a magnet I verified the parts were non-magnetic:

I installed the rivnuts with some JB Weld:

I made some wooden spacers to align the bracket and added the side skins temporarily:

According to the Garmin manual the magnetometer should be within 0.5 degrees of the longitudinal axis of the airplane. However on the VAF forum a Garmin employee explained this a bit more in detail: link

With a laser aligned with the longitudinal axis I verified that the alignment is within 0.5 degrees: