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Altimatic IIIB

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Well-Known Member
Dec 30, 2010
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The altitude capture and hold on our AP works great at 2000' and above. We can't set an altitude below 2000'. Also the calibration on the disk is at the upper limit. Example, at 5000' with the trim indicator nulled, the calibration/altitude disk is at the upper limit (you can't set it above 5000'.) I suspect at some point years ago, before we bought the plane, somebody removed the autopilot control console from the plane and moved the altitude setting knob or calibration disk before replacing it. We've been given 2 suggestions for correcting the problem 1) Go up to 5000' and set the AP to hold 5000'. Don't touch anything and land plane. Using the altitude selection knob move the selected altitude to 3000'. Disconnect the altitude selector flex cable at the console end. Turn the calibration disk to 1500'. Reconnect the flex cable, and you should now have the ability to set altitudes as low as zero and have 1500' feet each side of the selected altitude for calibration (As it is now when the altimeter settings are much above 30.25" we start running out of calibration capability.) 2) Disconnect the flex cable as before from the console end. Manually turn it full counterclockwise and turn the altitude set knob full counterclockwise to minimum altitude. Then reconnect cable.

The first solution seems the better one to me, but I'd like to get more input before the A&P and I change anything.

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