This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
When attempting to disengage the autopilot (AP), the servos refused to release control of the aircraft. The p-trim began raising the nose, while I pushed the nose forward to preclude a stall. Altitude was 9,500 feet.
When the AP would not disengage I pushed the disengage button on the yoke. When that didn’t work, I pulled the circuit breaker to the autopilot. That didn’t work either, the servos refuse to release. I then turned off the G5 flight instruments and the servos released.
After approximately 5 to 10 minutes I turned the G5 flight instruments back on and hand flew the aircraft to its destination.
I am having avionics technicians look at the autopilot and the installation.
I haven’t used the autopilot to much extent until yesterday.
Primary Problem: Aircraft
ACN: 1886057
I had a similar situation and actions when A/P disengaged for landing. I fought controls all the way to shut down. Ended up to be frozen flight controls after flight in mixed precipitation and decent to lower, freezing temps. I imagine the same could happen when ascending into colder temperature.
I’ve had a similar problem in a Saratoga. The Autopilot had to be replaced. There were too many things it kept having go wrong. Don’t remember the model number/name, but it was the one that shipped from Piper that has altitude hold, approach mode, auto trim etc. as opposed to single axis that only has a heading bug.
Letting the AP fly your approaches that you log for currency, can put you in a very bad place when you least expect it. One must fly to proficiency with approaches before letting George fly it all. That way when it malfunctions (like the above), you are able and ready to fly it all by hand.
Garmin autopilot with ESP?
This report would have been much more useful if we were told the make and model airplane and/or autopilot.
Skylane 182/RG Turbo Skylane/RG. Autoflight System. https://akama.arc.nasa.gov/ASRSDBOnline/QueryWizard_Display.aspx?server=ASRSO
My autopilot has it’s own master power switch. I assume all APs are also required to have one. I could only see this happening in my airplane if something in the servo system mechanically jammed. It’s designed to be overpowered by a pilot even when engaged.
Not necessarily. If the STC for the autopilot requires an independent switch then it should be there, but it typically is not required. However, an autopilot should have an independent master power feed. If it is wired directly to the buss then it should have an independent on/off switch, otherwise it could be powered from the avionics buss.
I’m confused why the pilot could not override the a/p? Even the bridle cables that attach the servos to the control cables are tightened to a limit and if the pilot yanks hard enough he should be able to overcome the tension of the clamps that hold the bridle cables to the control cables.
Think of an electric motor. It is an armature that spins on a couple of bearings and is motivated by brushes that apply power and make the armature spin (yes, oversimplified explanation for the technocrats, but that’s the way these things work). So what can make a servo jam? I just can’t see where this is possible. (I’m not saying that it didn’t happen, just that if anyone knows I’d like to hear).