What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

GMU 11 installation

Bavafa

Well Known Member
I am planning on installing my GMU11 in the wingtip, just wondering how people have determined the alignment of that. The install manual says within .5 degree of center line and finding that and transferring to the GMU 11 seems to be a near impossible task.

I was hoping to use the compass that is built into IPHONE but that seems to be very inaccurate as I constantly get a different result for a fix point and also using multiple IPHONEs have yielded different results. So it is rather unreliable tool for this use.

Does anyone know if the last wing rib is parallel with the center line?
 
My Iphone has a Level

You should have a Level app that was included with the latest software update. Look for "Measure". I use it all the time. My Iphone compass seems to work fine for me.
 
Last edited:
The wing ribs should be parallel to the centerline if everything was pre-punched. Unfortunately we locate the rear spar bolt hole and can have the wing swept slight aft or slightly forward.

The correct answer is going to be determined by the builder and how he does final assembly.

The installation spec for the GMU-11 is 0.5-degrees of the centerline. Does it really matter if the GMU-11 is oriented 2-degrees off the centerline? Yes it does if we are using DEAD RECKONING for navigation. Most of us now have GPS for navigation and when it quits, we should have a good idea where we are and be able to look out the window to get safely to an airport. IF flying IFR, we should already know what crab angle we were using and already on the required heading. IF there is more than 2-degrees of error in the install and the readout, the compass correction card should have a correction.

I installed my GMU-11 under the vertical tail. I retrofitted it into a flying airplane. My GMU-11 is not on the centerline but located on the right hand side of the aircraft. I lined up the GMU-11 with my eye to the elevator push pull tube. I followed Garmin's calibration and interference tests. I test flew on a day with NO wind. My GPS ground track agreed with the G5 heading number that the GMU-11 gave it.

IF you are concerned about being too far off of parallel to the centerline with the wingtip mount, I would like to suggest create the wingtip mount with a slot so that the GMU-11 can be corrected to the centerline with adjustments during fight test. Yes it will be extra work to fabricate, extra work to test, and extra work to adjust but in the end it will be as perfect as we humans can make it.
 
Back
Top