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Dihedral in RV14 (GMU-22)

Reflex

Well Known Member
I'm installing a GMU-22 magnetometer in the left wingtip of my-14. Garmin calls for the GMU-22 to be not only level with regard to incidence but also for dihedral. A couple of questions:

  • Anybody know what the dihedral angle is on the -14?
  • If you put your magnetometer in the wingtip, how did you make or shim the bracket to allow for the dihedral angle?
 
Whats wrong with the stock location and bracket?

Great question.

Too close to heated pitot wiring, landing gear, etc. Garmin recommends wing tip mount (Walt too). Hard IFR on this one.
 
Stock location and bracket works great, even with pitot heat and landing gear and unshielded light wiring, etc. Unless you use a pitot heat controller; which I can't see why you would need to.
 
Ha

If you follow all of garmin recommendations for location you will find the best place to mount the Gmu22 is 10 feet outside the fuselage, flying in close formation with the rest of the plane...
 
Not sure what hard IFR is but it works fine at the stock location regardless if you’re in IMC or VMC. Just about everybody uses the stock location for the GMU-22.

Anybody reading the thread use alternate mounting locations?
 
Putting it anywhere else is a pain. If I had to put it somewhere else it would be on a shelf in the upper mid fuselage. I don't have a shelf there......
 
+1 for using the mount

I put mine in the stock location, unregulated GAP26 pitot Heat, Vans (Stein) standard wiring harness, taildragger. Solid as a rock. It has flown several hours of actual IMC including rain and ILS and GPS/LPV to my personal mins of 500? and a bunch of acro too (THAT was in VMC:D). It passed all the interference tests, etc, flawlessly.

BTW - I didn?t even use a twisted pair for my pitot heat wiring. Just ran a ground up to the block on the firewall. GMU-22 didn?t even flinch during the interference test when I turned it on. Biggest reaction was when I moved the stick left and right. Go figure...

Just my opinion, but I have had zero problems using their suggested location. I believe Vans -14 has a Garmin panel and that plane has tons of hours flying all over the place. Not sure, but I bet theirs is in the same place. Scott would know.
 
Not sure what hard IFR is but it works fine at the stock location regardless if you?re in IMC or VMC. Just about everybody uses the stock location for the GMU-22.

Anybody reading the thread use alternate mounting locations?

I put mine in the left wingtip. After my friend had continuing issues with his GMU-22 in the stock location, which were resolved by moving it to the wingtip, I decided to follow suit. Vic also told me that he didn?t have problems with the factory plane, but if he was building, he would put it in the wingtip. It was an easy change. I just had Stein make the harness they build for Van?s ~10? instead of 2?. Have not had a problem with it. Another buddy has his in the stock location and has not had problems. Your choice. Do you feel lucky? :rolleyes:
 
I put mine in the left wingtip. After my friend had continuing issues with his GMU-22 in the stock location, which were resolved by moving it to the wingtip, I decided to follow suit. Vic also told me that he didn?t have problems with the factory plane, but if he was building, he would put it in the wingtip. It was an easy change. I just had Stein make the harness they build for Van?s ~10? instead of 2?. Have not had a problem with it. Another buddy has his in the stock location and has not had problems. Your choice. Do you feel lucky? :rolleyes:

Do you have the info the OP was looking for?
I'm interested .
 
I just bought the mounting bracket Garmin makes for the GMU-22 and mounted it about mid-chord on the left wingtip. I have no idea about the dihedral, but it works perfectly.
 
one solution is
https://www.steinair.com/product/gmu-22-wing-tip-mount-right/

or google these for more ideas for brackets
"wingtip magnetometer mount", or
"Dynon wingtip magnetometer mount"

for alignment use a smartphone digital level on the center spar carry through to get airframe level and translate same angle to the mount sideways axis. than use your phone for the panel angle measurement plus 90 deg for front/back axis of the bracket.

If possible mount the magnetometer as far back on the wing rib as practical to minimize lamp/strobe/ads-b interference (if applicable)
 
If I were building an RV-14, I would put the GMU 22 in the wingtip--personal preference after having mounted several in different airplanes. It's just going to give you better odds for good performance and maximizing the interference test results.

So, Garmin specifies a 3° tolerance from level flight for the GMU 22. I would attach the mount to the wing tip equidistant from interference sources and then level it with a digital level with the aircraft set at level flight attitude. Shim as necessary. Close enough.

Note: If the RV-14 has the iron pipe in the aileron leading edge, you should mount the magnetometer about half way on the chord line--avoid interference equally from tip lights and the iron pipe in the aileron.
 
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Just as a data point my regulated pitot is in the same wing .. but I grounded it next to the unit vs running the ground all the way back to the fuse.

I can see where running a power and ground next to the magnetometer might cause interference.

But no issues in 200 hours.

(I have a thread out there where my first GMU-22 was bad and I was dragging the airplane all over the field in 100 degree Alabama humidity - which translates to no less than 1,000,000 actual degrees - trying to calibrate it .. I think I lost about 20 pounds that day :D)
 
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Not to change the subject but why are you putting a GMU 22 in your RV14 and not a GMU 11? I know RV14s are fast but not fast enough that they require a GMU 22 instead of an 11 and since no one has asked that question, I'm assuming this is common or suggested for some reason. . . I'm just asking to learn. No other reason than that.
 
Not to change the subject but why are you putting a GMU 22 in your RV14 and not a GMU 11? I know RV14s are fast but not fast enough that they require a GMU 22 instead of an 11 and since no one has asked that question, I'm assuming this is common or suggested for some reason. . . I'm just asking to learn. No other reason than that.

Good question. I'm using the -22 because I didn't want to run the canbus all the way to the wingtip. My electrical scheme works better making the aileron servo and the elevator servo the ends of the canbus.

A couple of notes:

  • Got a note from tech stating that the dihedral is 3.5 degrees
  • I'm using the bracket from Stien, but it does NOT have the dihedral angle built in.
 
  • Got a note from tech stating that the dihedral is 3.5 degrees
  • I'm using the bracket from Stien, but it does NOT have the dihedral angle built in.

Interesting. Seems to work without any shim, though. YMMV. :rolleyes:
 
No joy getting my GMU-22 to calibrate

I have tried to calibrate it about a dozen times now. I have tried various different places at two different airports. I bought a handheld compass to ensure I had it right on magnetic north (apparently a compass rose painted on the asphalt is not a thing any more). I tried it with the engine running and I tried it with two guys muscling my airplane around in circles.

I put my magnetometer in the tail, using the SteinAir bracket riveted to the first rib behind the access panel. This was as per Stein's recommendation.

I am thinking I should have put it in the standard location in the left wing near the temperature probe. I think it will be three to four hours of work to redo it.

For some reason I was under the mistaken impression that once the airplane was flying there was nothing left to do...

__________________
Bruce

2003 RV-8, N297NW, bought, flown, sold (~600 hours)
2007 RV-10, N662G, bought, flown, sold (~700 hours)
2020 RV-14A, N662F, mostly done (5 hours into Phase I)
 
Since you have it in the tail, and a lot of people have put it in the tail (not a 14 but on others).... one would think it would work fine. You might want to check and recheck your wiring and make sure two wires aren't backwards.

Also, you will want to find a pad on your airport where there is no rebar in the concrete. I've heard tell of that interfering. Our airport does not have a compass rose but has an asphalt area just as good. You could try that; or find some hard grassy area?
 
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Magnetometer problem solved!

It turns out that I had installed it upside down...

Apparently this is not uncommon. I spoke to Stein at SteinAir and it was the first thing he had me check. He said that he couldn't really give me a hard time since they see so often.

After I corrected my mistake, I did the calibration and it passed on the first try!

Woo hoo!

Bruce

2003 RV-8, N297NW, bought, flown, sold (~600 hours)
2007 RV-10, N662G, bought, flown, sold (~700 hours)
2020 RV-14A, N662F, built, in Phase I
 
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