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Have seen some improvement although still not perfect. Started a new thread " am I expecting too much from my EFIS" with some results |
Just another data point. We have the same system, the Horizon HXR, with the magnetometer in the tail and the AHRS on a shelf between the panel and the luggage compartment. Installed in February. No problems.
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want to do it right the first time
Getting ready to install magnetometer in right wingtip against the outermost rib in my 6A. A check with the iPhone compass app shows no disturbance in The Force with nav lights or landing lights or aileron movement.
Do I align the magnetometer base parallel to the longeron (where I would rest my elbow when the canopy is open) for a level datum? Just checking that that's the desired level reference. -Stormy |
spoke too soon
After I drilled holes for the magnetometer bracket in the outboard right wing rib, I rechecked the magnetic interference status with my iPhone 5S digital compass and the results were NOT as before. For a mounting location, I had split the distance between the aileron counterweight pipe and the conduit aft of the spar that carries the landing light and nav light wires.
I found a 3 degree variation in reading when moving the aileron to its full limits of travel, and a 7 degree variation switching the landing light on/off. When I checked a few days ago, it was 1-2 degrees max. (Didn't bother checking the nav light this time, since the landing light interference is a show-stopper.) Then I reset the iPhone to try again with a fresh calibration. The compass reading swung from a steady 76* to 83* when the landing light was turned on -- and remained at 83 degrees when the light was turned back off. I can't understand how a flux gate compass can get "stuck" in a new position, but that was what seemed to be happening. The upshot is I no longer trust the iPhone compass functionality. To avoid real headaches for myself later in the install, I am going to invest in a Silva compass or something analog and old-school to evaluate potential magnetometer locations. I'm already thinking that shortening the conduit back one bay from the tip and drilling a hole through the spar web for that landing light wire might not be sufficient to get rid of the interference. The light grounds directly to the frame, so there is no way to twist a ground return lead with the B+ wire and cancel the magnetic field. I may be joining the ranks of those who mount their magnetometer in the tail cone somewhere. I wonder if under the empenage fairing is a workable place. Big bolts nearby, I suspect. This is a disappointment, as at first look, it seemed the magnetometer in the wingtip was going to be bolt-and-fly easy. :mad: -Stormy |
Just a note, the iPhone compass is notoriously bad and relies heavily on a GPS signal. The iPhone 6 is better, but the 4 and 5s aren't very good.
You might consider wiring up a long harness to a magnetometer box and use the GRT display to see variance in the readings. With a long harness you could temporarily affix the magnetometer where you intend to try installing it. |
After further research...
I think the consensus is the tail cone shelf below the VS is usually a reliable magnetometer location on the -6A and similar.
The only hassle is the wiring; no pre-installed conduit there like I had in the wing.:( |
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