Autopilot "convulsions"

TommyLM

New Member
Joined
Feb 22, 2020
Messages
3
I have HDX1100 x2, with autopilot with remote knob control panel. Recently I sent in to Dynon my roll server for repair. The problem: I have had the autopilot do something really screwy. (I have had a previous issue with having to replace the shear pin in the roll access servo for a problem I could not identify). Sometimes when using the autopilot in expert mode and using tracking, I will get a message over the headphones which says "Autopilot" which I have learned means the autopilot has been seemingly disconnected, but without my command. Sometimes I just turn it back on but sometimes I notice (and I have witnessed on the ground that the roll axis is behaving somewhat erratically, going back and forth but without any purposeful movement, like it is having a "seizure.") Also, at the same time, the pitch axis is completely disconnected and is the elevator is free. But the autopilot is not really off. When it starts doing this you cannot turn the autopilot fully back on. Nor can you turn it fully off unless you pull the breaker . The affect in the air, is the roll servo "fights" manual input but is unable to overcome manual control. It sort of feels like when the power steering belt breaks while you are driving a car. The shear pin has not been overloaded either. Dynon suggested that the servo was defective so I sent it in for repair. Any ideas about the autopilot problem. Could the cheap serial connectors be the culprit?
 
Last edited:

jakej

Well-Known Member
Joined
Oct 10, 2007
Messages
2,079
Location
Adelaide, Australia
Crimped, correct ? did you give a gentle pull on the wires to confirm the pins are locked in place ?
The wiring - premade or self made ? Separate power, 20 awg wire to the servos & not just connected using a Dynon SPL (splitter) harness ?
Have to ask as we can't see the wiring & need to get down to basics with troubleshooting.
 

TommyLM

New Member
Joined
Feb 22, 2020
Messages
3
Wires on the servo end seem well anchored. Are you suggesting that a loose fitting wire could do this? I have had my suspicions because the DB9 fitting on the wire which leads to the glass panel seems lightweight and is missing a few unneeded pins . I know that serial connections do not require all the of the 9 pins necessarily. I do not know if Dynon sends these to the installer pre-wired with connectors or if the installer has to pin out the connectors manually. I have had my suspicions of the connector on the panel side of things for a while. Sometimes the AP would just disconnect without warning. Then it would magically reappear with the next flight. I have a feeling the pin out was done by the installer. I know that when Dynon sent me a new updated transponder, they included a manual pin out kit which I didn't use. I may look in the Dynon installation manual for the pin out diagram. Thanks.
 

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