The SV-ADAHRS-200 installed in my aircraft, a Zenith CH650B, is mounted just forward of the belly access panel of the fuselage on the pilot's side. I did not build this plane; it was built in 2015, been flying ever since, and I bought it about a year ago. It is well built. I've put a little over 60 hours on it and it doesn't exhibit any bad behaviors. However, there does seem to be some discrepancy between what I see as my landing crab angle and what the data recorded by the SkyView captures. In investigating that discrepancy I checked the alignment of the ADAHRS to the roll, pitch, and yaw axis. Roll and pitch are spot on, less than 0.1 degrees (within the accuracy of my instruments). Yaw is more difficult to determine. I compared the ADAHRS to the two closest fuselage stiffeners that run horizontal (right angle) to the nose/tail. Using this method, the yaw alignment measure about 2 degrees out. The installation of the ADAHRS calls for the alignment of all three axis to be less than 1 degree. Being an engineer and knowing "better is the enemy of good enough", is it worth messing with this? I'm afraid of the ripple effect, i.e., will this change the indicated stall speeds, will the AOA need to be re-calibrated, will the autopilot need to be re-calibrated. What can of worms am I opening up?
SV-ADAHRS-200 installation & alignment
- Thread starter BlueCrab
- Start date
Rhino
Well-Known Member
- Joined
- Jul 20, 2009
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- 1,663
Stall speed is manually set, and should not change. AOA is driven by air pressure, and not dependent on the orientation of the ADAHRS. In short, those worms should stay in the can. Whether or not it's worth it is up to you, but the re-calibration of those things would not be a major effort in any case.
So, just to put a lid on this, the discrepancy I was seeing in the landing crab angle (which also showed up in the wind direction) was corrected by performing a ground and inflight compass calibration. I did adjust the ADAHRS to align the yaw axis, but this has had no dramatic effect (at least none that I've seen yet) on anything. Perhaps time will tell.