Helicopter Gross Weight and Center of Gravity Measurement System

The design of an on-board gross weight and center of gravity measurement system applicable to the CH-47 and UH-1 helicopters was developed, and a prototype CH-47 system was evaluated in the laboratory. Gross weight accuracies of plus or minus 1.6 of maximum design weight were achieved in a laboratory simulation of the environment. A flightworthy prototype was subsequently fabricated and evaluated in flight tests on a CH-47 helicopter at the U.S. Army Aviation Systems Test Activity, Edwards AFB, California. The results show accuracies of plus or minus 1 full scale with the helicopter in a rotors-static condition. With rotors-in-motion, however, errors up to 5000 lb occurred in the gross weight due to the inaccuracy of the rotor lift measurement. It is concluded that the method of measuring rotor lift via rotor structural stresses is viable, but further investigation is required into the nature of the thermal stresses and dynamic forces induced by hot lubricants and pitch actuator cylinder.