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Old 03-20-2017, 08:56 AM
Tankerpilot75 Tankerpilot75 is offline
Join Date: Jan 2015
Location: Oklahoma City, OK
Posts: 102
Default GRT and Dynon D10A magnetometer in same wing tip

When I purchased my RV7A from the original builder both magnetometers were mounted on the shelf just forward of the vertical stabilizer. As a result, every time I keyed the radio, magnetic interference was so great that both my GRT EFIS and my backup D10A headings would drift. The drift was so bad that I literally had no idea which was the most correct (neither were very close to actual magnetic heading). ForeFlight got me from Denver (where I bought the plane) to my home in OKC.

After talking to GRT and Aerotronics (who built my panel) I decided to move both magnetometers to a wing tip position. Originally I was going to put them in separate wing tips but D10A wire length limits forced me to place them in the same wing tip. I did my best to ensure appropriate separation from strobe and other electrical interference and paid very close attention to their alignment to within 2 degrees of level to the AHAR units.

I can report that heading differences between the dual GRT Horizon WS and my Dynon D10A have, since this move, (about a year and a half ago) at all times remained within one to two degrees of each other and actual magnetic heading. Strobes, landing light wires, and relatively close proximity of the two magnetometers (about a foot apart) to each other do not appear to impact headings. There is more than 18" distance from the landing and strobe lights from the magnetometers.

I also want to thank Pat Hatch publicly for his patience and support when I installed my Tosten multi-function grips last fall. Without his assistance that effort would have been a disaster. His "Ultimate Hub" is a truly great trim controller.
Jim H.
RV7A - N523RM
Retired KC-135A/E/R Driver - Desert Storm Vet (USAF)
Vietnam Vet (US Army)
2017 Contribution: 12/17/2016
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Old 03-20-2017, 09:07 AM
Pat Hatch's Avatar
Pat Hatch Pat Hatch is offline
Join Date: Jun 2006
Location: Vero Beach, FL
Posts: 735

Originally Posted by tgmillso View Post
How about the nut plates for the wing tip attach screws? I don't seem to be able to find any #6 size made of stainless. Is using steel Ok in this situation, or will it affect the magnetometer?
Tom, I'd be more concerned about anything ferrous that moves. If it's stationary, not as much of a concern. We did use the stainless screws but the nutplates are just the regular ones. You should be fine. You'll discover any problems when you do your magnetometer interference check.
Pat Hatch
RV-4 (Gone to RV heaven)
RV-6 (N44PH - Flying)
RV-7 (Sold)
RV-8 (Helped build Bob Lund's airplane) Trim Relay Boards/Wiring Hubs (Photography)
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Old 03-20-2017, 05:52 PM
tgmillso tgmillso is online now
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 297

Pat, you just made my day (then again, I'm current working in the canopy, so any good news makes my day).
Other builders here have been telling me I should make a composite strip that the stainless screws bite into, however I was concerned about the longevity of such and would have rather just use nut plates, so thanks for confirming that it should work ok!
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Old 03-21-2017, 12:03 PM
bill v bill v is offline
Join Date: Mar 2011
Location: zeeland michigan
Posts: 106
Default above a wing access plate?

I plan on the wing tip but since the inspection plates have fewer screws to remove what would be wrong with above the second inspection plate behind the fuel tank on that rib?
built rv-4 started 1987 finished 1996 now building rv-7, fitting cowl
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