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Matt Dralle's RV-8 Project
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Date: 2-8-2009
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Number of Hours: 2.00
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Manual Reference:
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Brief Description: AHRS Bracket Pitch & Roll Alignment - Part 1
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The AHRS needs to be mounted nearly perfectly level both in pitch and roll directions. Since I was mounting mine off the instrument panel, this presented some challenges since the angle of the instrument panel was only exact when the top skin was cleco'd on. But, with the top skin cleco'd on, there was no way to adjust or otherwise observe the orientation of the AHRS bracket. To assure that the AHRS was securely mounted, I devised an additional rear attachment point that tied into the #2 bulkhead. The catch was that it had to be disconnectable to allow the instrument panel to be removed. After a good deal of thought and planning, I came up with the scheme shown in the pictures. It seems to have worked out well and can be disconnected either from under the instrument panel or from the baggage area with an Allen wrench.
To get the angle just right, I mounted the AHRS and primary EFIS in the panel, clecoed the top skin on, then reached under one side of the skin and adjusted the bracket to get a near-perfect pitch and roll alignment. I took the skin off and then used a long piece of masking tape to pull the instrument panel back into the correct vertical alignment using the artificial horizon display on the EFIS!
You can see from one of the pictures that the pitch and roll alignment came out nearly perfect and is within +- .2 degrees in both pitch and roll. The AHRS output seems to drift about that much anyway, so I'm gonna declare my alignment prefect. Notice that I had a digital level in both the pitch (orange one) and in the roll (yellow one) axis of the fuselage. I shimmed up the fuselage to get the levels to report 0.0 degrees and then adjusted the AHRS bracket for level.
In the installation manual for the AHRS/EFIS, they indicate that you should just put a bubble level on the top of the AHRS to get the Pitch and Roll axis adjusted. That would only get you within a couple of full degrees if you're lucky, so being within .2 degrees in both Pitch and Roll, seems like its pretty good.
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Left Hand Side Platenuts and Bracket Attachment Points
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Left Hand Side Platenuts and Bracket Attachment Points
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Right Hand Side Platenuts and Bracket Attachment Points
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Copyright © 2008-2024 Matt Dralle. All Rights Reserved.
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