Matt's RV-8 Project



Matt Dralle's RV-8 Project
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Date:  3-6-2010
Number of Hours:  3.00
Manual Reference:  
Brief Description:  GRT Magnetometer Installation In Tail - Part 1

The GRT EFIS's use two, redundant electronic compass modules called "Magnetometers". These units literally measure the earth's magnetic fields and provide a direction in much the same way a wet compass does. Needless to say, they must be mounted away from stray magnetic fields such as the radios and other electronics. GRT recommends the fiberglass wing tip, but this presents some problems because the cables connecting to the units have a great many wires. Since all of the wiring from fuselage-to-wing has to be connectorized, I opted for an alternate location that wouldn't require the extra connectors. This location turned out to be the area under the Vertical Fin, in the area between the Horizontal Stabilizer ribs. There are no other RF sources back there and a minimal amount of Ferris metal.

I mounted the first unit on a set of aluminum rivnuts squeezed into the fuselage web and a set of aluminum standoffs. I added another set of standoffs and then mounted the second unit on top of the first, securing with Nylon screws. I replaced all of the steel DB9 connector hardware with brass screws and washers to avoid any issues with Ferris metal.

According to the diagnostic readout on the EFIS, I managed to mount the top and bottom magnetometers within 1 degree of each other! They seem to be correctly reporting directional position, but I'll know for sure once I taxi out to the compass rose near the runway for calibration.
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Paperdoll Pattern For Magnetometer

Paperdoll Pattern For Magnetometer

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Holes Drilled

Holes Drilled

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Rivnuts Added

Rivnuts Added

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