Look up autogyro "buntovers", not direcly applicable, although they are in an established autorotaional state. Quote from here:
Popular Rotorcraft Association :: Gyroplane Stability
"Power Push-Over is just one form of what is also called a "bunt-over". These typically refer to the gyro pitching rapidly forward to inverted. This typically results from an unbalanced propeller thrustline that tends to rapidly rotate the gyro forward once the rotor looses significant lift and drag (thrust).
A "bunt-over" is typically considered to occur from any or all of several factors:
Pilot rapid forward cyclic stick motion causes reduced rotor lift and drag, allowing the rotor to slow, perhaps too much!
A strong wind down-gust disturbance which also "unloads" the rotor - reduces rotor lift and drag.
Upon severe and/or extended loss of lift, the rotor slows below its ability to autorotate and support the gyro's weight.
An unbalanced propeller thrustline offset pitches the airframe rapidly nose-down upon loss of rotor lift and drag.
The unstable airframe, pitching rapidly nose-down results in moving the rotor thrustline forward, relative to the CG, causing further nose-down pitching in reaction to reducing or negative rotor thrust."