Performed ADAHARS (Garmin installation manual 35.4.7) and Magnetometer GMU 22 Calibrations (Garmin 35.4.8). First steps required good GPS satellite reception, so moved to front of hangar. Very hot and muggy, so I set up fan blowing into cockpit to keep me "fresh". Leveled longerons F/A and SxS = Flight Level using wing jacks. Confirmed GSU 25, Air Data and GPS all checkmarked green. Since Unit Orientation previously set (Tubes forward, Connectors Down) repeated AHS Pitch Roll Offset: 8.2 deg Pitch Tilt (angle of Instrument Panel) and 1.0 deg Roll Tilt (must be within panel, G3X and GSU 25 mounting, since plane otherwise was really close to level). Not ready for Engine Run-Up Vibration Test, and Static Pressure Calibration is only needed IF fail altimeter test. So performed Magnetometer Interference test (Garmin 35.4.8.2). Sequence of turning on/off electrical components and moving flight controls in 10 sec intervals was 32 steps. Seemed A-OK as test progressed, with only minor % of limits displayed - unit very last steps turning Pitot heat on/off. Failed with 793% over limit. Per instructions, called Garmin prod support for guidance. They indicated either power wire routed too close to Magnetometer in wing, OR not grounded correctly. Recommended I consult with Vans. [ note: I already routed power wire away from Magnetometer during assembly after recommendation from Mitch Lock who had just built his RV-14A with essentially same Garmin components ....this was prior to Mitch becoming Van's president] Here's prior build log entries for GMU 22 install/wire routing, and GAP 26 Pitot install. While waiting on contact with Vans, Christer at Stein Air confirmed need ground wire routed all the way back to side of Fuselage - not adjacent to Gap 26. This "cancels" the magnetic field being generated by the power wire. So, with difficulty via access panels on bottom of wing, I routed 14 ga wire (same size as power wire) along power wire, then attached to Fuselage. (note: I had to use red 14ga wire to get it done immediately, so any later diagnosis will be challenging w/o a black wire) Success ! Passed - now only 10% of limit for Pitot Heat, which fades to zero quickly. It took me a few hours to route, but very satisfying to resolve so effectively. Now I can focus on getting ready for engine start and final steps for Airworthiness Inspection....soon.
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| Plane leveled, and receiving excellent GPS coverage. Set up fan to keep me fresh on a HOT, muggy day. Since wing jacks are further forward than main gear, the plane willdrop it's tail when getting on rear step- so support at rear is critical |
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| Old tennis balls on sharp corners, including propeller protect me and plane |
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| Kinda shocked how much over the limit Pitot Heat caused. Later realized brightness set on manual, vs photocell automatic. |
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| Prior to routing ground wire along Pitot Heat power wire (red). It's optical illusion blue AOA line looks squeezed by nylon tie |
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| "War wounds" from sticking arm deep into wing to reach tight spots for routing ground wire. These edges are all deburred, but I had so much pressure on thin edge to get my big arm into position, the one along wrist actually cut through my skin. Geesh ! It didn't matter once it Passed the interference test |
