Ricky_231 Posted May 2, 2020 Report Share Posted May 2, 2020 A few flight hours ago, my Century 41 AP started acting up - it'd porpoise if I hit ALT mode before stabilizing after climb/descent. Fine. I thought it was just a matter of not abusing the system - so I started leveling off first, then hitting ALT. No problem - super smooth sailing. Now the past 2 flights, there's nothing I can do to stop it from porpoising. And it gets pretty violent so I have to turn it off after 2 - 3 cycles. I can tell it's having a delayed reaction - it'll be pointing the nose down, starts picking up speed and pitch up, then rolls the trim up (and vice-versa). Has anyone here had a similar issue? Was it an easy fix (reprogram/calibrate the unit) or something more complicated. I just had the Attitude Gyro overhauled a few months ago because it had an issue.. hope it's not it again. Thoughts? Quote Link to comment Share on other sites More sharing options...
carusoam Posted May 3, 2020 Report Share Posted May 3, 2020 Sounds like a typical challenge for servos with clutches... the clutches wear continuously... They get to a point where they misbehave... slipping clutches cause the system to not know what it is doing... Strange behavior follows... PP thoughts regarding some servo motors, not particular towards, Century APs... What model number Servo do you have, when was it OH’d last, and who does the OHing... typical questions to follow-up... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
N231BN Posted May 3, 2020 Report Share Posted May 3, 2020 Turn off the electric trim switch in level flight and see what the AP does. My trim constantly hunts up and down so that is my SOP once in cruise. It does not porpoise though. Quote Link to comment Share on other sites More sharing options...
Ricky_231 Posted May 3, 2020 Author Report Share Posted May 3, 2020 6 minutes ago, N231BN said: Turn off the electric trim switch in level flight and see what the AP does. My trim constantly hunts up and down so that is my SOP once in cruise. It does not porpoise though. I'll try that Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted May 3, 2020 Report Share Posted May 3, 2020 Also, try lubing the control shaft. People have had porpoise problems with other autopilots recently that were caused by just a tiny “sticky” spot in the elevator control which were resolved with LPS 2 or similar. 1 Quote Link to comment Share on other sites More sharing options...
Ricky_231 Posted May 3, 2020 Author Report Share Posted May 3, 2020 Just now, Ragsf15e said: Also, try lubing the control shaft. People have had porpoise problems with other autopilots recently that were caused by just a tiny “sticky” spot in the elevator control which were resolved with LPS 2 or similar. Ha - that's what I was hoping to hear. When I was pre-flighting today I felt the elevators were a little 'sticky' as you put it. Didn't connect the dots - but that's the sort of thing I was hoping for. I'll try lubing it up tomorrow while rationally trying not to be too optimistic :-) 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted May 3, 2020 Report Share Posted May 3, 2020 Lubing the controls has a great affect... Keep in mind there are many plastic guides that the tubes go through... Fortunately... the elevator is pretty easy to access a lot of the parts... ailerons would cause going out into the wings to inspect, clean, lubricate... Might be a good idea to check out the MM for where any guides or bearings may be hiding... The better hidden they are... the more likely they have been missed.... PP thoughts only, not a mechanic... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
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