Originally Posted by
AvionicsWiz
A sudden medical issue wouldn't explain the unstable altitude control during the flight.
In a trimmed condition, an airplane will settle at an airspeed and altitude. It may climb (if trimmed up) until engine power is reduced by the thinner air before it levels out, or descend into the ground if trimmed for a descent.
However, no trim level will result in the plane going up and down and up and down like this. This to me looks like a Trim Runaway event (which is why current autopilot installations put "kill switches" right in the pilot's field of vision.) Mine are directly below the HSI. Flip the trim switch off, trim is dead. Flip the autopilot switch off, the autopilot is dead.
For a trim runaway to happen, autotrim has to be installed and has to malfunction. It has been established that this aircraft was not equipped with autotrim. So that isn't a potential failure path.
You pull back the throttle to flight idle.
Extend the landing gear (knowing you are beyond legal extension speeds of 144 kts probably, and will lose or damage your gear doors.)
If you are going down fast, both of those actions will:
1. Slow you
2. Cause the plane to level slightly due to the drag.
They cannot be seen by the passenger. They are on the pilot side of the center column, which includes the nose gear position indicator.
I don't have any pictures which show this. The next time I'm in the area, I'll snap a shot. I'm grounded due to COVID-related heart issues at this time, so I haven't been flying.
Care to elaborate the described behavior of trimmed/untrimmed general aviation aircraft?
-M-