The big turbo-prop planes like the C-130 and P-3 have a "de-coupler" between the propellor and the gearbox to the turbine, that disconnects the propeller if the motor fails, and the propellor can't be feathered, and goes into low pitch.
A low-pitched windmilling propellor attached to the gas generator can create enough drag to overcome the control authority of the flight controls, so a Bellville spring pushes the propeller out of engagement with the shaft. The prop still windmills, making an awful shriek as the blade tips go supersonic.