GMU 11 Issue

[ColoradoSolar]

I installed a G5 system in my RV-6A consisting of a G5, GAD13, GMU11, 2xGSA28 and a GMC507.

My G5 reads about 5 degrees to the right when tracking down the runway (either way). I have run the interference test multiple times with very low interference and the calibration a few times with no improvement. The GMU11 is installed in the tail right behind the last bulkhead before the fairing. There are no lights installed in the tail on my plane so that only wires going back there are the power and can bus wires to the GMU11. No can bus errors on any of the devices and everything seems to be working fine except the GMU11 calibration.

If I don't start the calibration within +/-5? on north what will happen? I am using the compass in my iPhone to get close as I can, there is no compass rose at my airport.

Now if I can get the crazy wind to die down I can get back out there and play with my new toy.

[rapid_ascent]

Two thoughts:

1) Are you sure that the GMU 11 is aligned to the longitudal axis of fuselage?
2) What type of mounting hardware did you use? 316SS?

[ColoradoSolar]

Originally Posted by rapid_ascent

Two thoughts:

1) Are you sure that the GMU 11 is aligned to the longitudal axis of fuselage?
2) What type of mounting hardware did you use? 316SS?

I aligned it to the bulkhead which looks like it should be very close to the longitudinal axis.

I used the SS mounting hardware that came with the GMU 11.

[DeeCee 57]

Eric, are u using the runway numbers or the actual QFU for that runway?
Maybe you?ll an answer in this very recent thread http://www.vansairforce.com/communit...d.php?t=181890

[ColoradoSolar]

Originally Posted by DeeCee 57

Eric, are u using the runway numbers or the actual QFU for that runway?
Maybe you?ll an answer in this very recent thread http://www.vansairforce.com/communit...d.php?t=181890

Dan,

Thanks for the push in the right direction. My airport is so small that I couldn't find the magnetic heading listed anywhere. So I just calculated it from the coordinates of the ends of the runway and once I added magnetic variance I ended up with the numbers I was seeing in the G5. When I get a chance to go flying again I am going to head to a nearby airport that I do have magnetic information for and check there as well.

[64wing]

I strongly suggest you simply fly to an airport with a surveyed compass Rose and recalibrate the gmu. Remember: runway numbers are simply rounded to the nearest 10 degree increment of the magnetic circumference. The GMU itself needs to be within 2 degrees of the longitudinal axis of the airplane for best results. Since you have a G5, run an interference test with it but make sure you record readings with full deflections of the controls (elevator, rudder, flaps, and ailerons). Since your interference test hasn't exceeded 100% I would imagine your location is just fine. Lastly, when you installed the G5, did you level the airplane and allow the AHRS to level? Just a few things to check...I install these a lot

[ColoradoSolar]

Originally Posted by 64wing

I strongly suggest you simply fly to an airport with a surveyed compass Rose and recalibrate the gmu. Remember: runway numbers are simply rounded to the nearest 10 degree increment of the magnetic circumference. The GMU itself needs to be within 2 degrees of the longitudinal axis of the airplane for best results. Since you have a G5, run an interference test with it but make sure you record readings with full deflections of the controls (elevator, rudder, flaps, and ailerons). Since your interference test hasn't exceeded 100% I would imagine your location is just fine. Lastly, when you installed the G5, did you level the airplane and allow the AHRS to level? Just a few things to check...I install these a lot

How do I find an airport with a compass rose? I have searched with no luck. I was not just going off the runway number but getting the magnetic heading from the AF/D.

I have run the interference test multiple times following the instructions in the G5 installation manual and the highest reading I had was about 20%. I did level the plane before aligning the G5.

This is all good info.

Thanks,
Eric

[Thermos]

...they paint compass roses all over the country! Perhaps one of the airports on this page is close to you -

http://colorado99s.org/airmarking.aspx

HTH

Dave