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Wiggling ASI indicator needle and A/P malfunction

“Better not check a runnung system more often than necessary”: After a CAMO stipulated “regular” performed pitot/static and avionics-test the ASI indicator needle is wiggling now.
I was wondering what was done in this check at all while during the subsequent flight the AP (KFC225) showed a complete malfunction not keeping roll or pitch anymore, too. the other thing I was wondering about is that the avionics technician mentioned that this would have been the “last time that any calibration would be possible” since now.
Next time, the avioncs technician siad “some parts including the KDI 572 would not be servicable any longer because of the end of calibration possibility”….(???). Would be happy if soemone get the things sorted out, although embarrasing myself in posting that kind of foolish questions. Thanks @Lucius for the pic of the ASI which I used from an older posting- hope that this is OK while having the same instrument in my TB20GT.

TB20 Airman
Borkenberge EDLB, Germany

Normally, instruments wobbling around suggests they are in need of an overhaul. This is generally true for an altimeter. The ASI, I don’t know but suspect the same.

I would get a leak test done on the system (like one does on an N-reg every 2 years) and if no leak is found, change or repair the instrument.

The KDI572 needs no calibration (it’s a front end for a KN63 remotely mounted DME, as installed in a TB GT) so that’s complete nonsense. They can still be bought new, for a few k, but plenty come up on US Ebay. Maybe the solution for that one is a change of “avionics technician”

Shoreham EGKA, United Kingdom

Yes, however and it could actually be that during testing the diaphragm/“expansion vessel” in the ASI was damaged :-(

Perhaps the the avionics technician meant the KEA-130A altimeter which I thought is encoding for the KFC 225, but as far as I remember the A/P get´s its altitude information from another encoder, right – That means that I hope the KFC is rock soild enough not having been damaged, if not the whole bunch of servos burnt out or there is a signal problem from the Bendix KI256 FCI? Well I will do a leak test and report to the forum. Always glad if one has an idea.

TB20 Airman
Borkenberge EDLB, Germany
3 Posts
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