US Patent 7983804 System for minimization of aircraft damage on collision

A system for minimizing damage on collision to a vehicle having at least one self-propelled wheel is disclosed. The system comprises a motor in a wheel of said vehicle which drives the vehicle, means for measuring the speed of said wheel, means for measuring the torque of said motor, means for monitoring the ratio of the torque of the motor to the speed of the wheel, and means for stopping said motor when torque:speed ratio exceeds an acceptable value.