M,
For some reason, the engine would idle normally on the ground, but in flight would idle down and stop. Was strange and counter intuitive.
My best 'guess' would be induced prop drag due airspeed. I used to operate a C206 that would slow the idle when turning right due (I'm told) to gyroscopic propeller influences. Never occurred when turning left.
An aerodynamicist or engineer may have a more qualified answer.