Fellow rotorheads,
A gyro cannot experience mast bumping in the same way a heli does. There is no mast to provide torque. The rotor is allowed to spin on a bearing.
Negative g is still a problem because it leads to loss of attitude control.
This is true of all teetering rotor systems.
Loss of rotor authority means that the gyro can rotate itself right into the rotor, usually chopping the tail off.
Another area of concern is PIO or pilot induced oscillation. This usually happens with low time pilots who chase the controls and wind up doing a series of porpoising manuevers that get progressively worse culminating in a tail boom strike or other catastrophe.
A horizontal stabilizer of adequate proportions can vastly improve the damping and control response and reduce the PIO danger.
Incidentally, engine failure results in more than "a gentle glide". A steep glide must be entered to maintain forward airspeed.
At the bottom, similar to a heli, a flare is entered to build energy in the rotor.
There is no collective to pull, the flare is used to cusion the touchdown.
[This message has been edited by Try_Cyclic (edited 24 June 2001).]