622. C-5A Integral Weight and Balance System

Paper

Abstract

The C-5A cargo airplane will transport large volumes of military cargo between relatively undeveloped bases. Electro Development Corporation has developed the on-board weighing system which will serve as a primary load control system.
Transducers mounted on the outside of the landing gears measures shear displacement. Information voltages are displayed as weight, center of gravity, in the electronic control unit which mounts near the aft cargo door.
Sensors are flexured displacement cells ‘butt’ mounted to pads forged on the landing gear. Machining tolerances in the landing gear are compensated by a Clamped Cone adjustment. This unique mounting method eliminates all slippage of the transducer which could cause zero shift during operation.
Several electronic refinements are employed to achieve measurement accuracy approaching one percent. Three hundred Hertz excitation voltage eliminates noise pickup, a ‘closed loop electronic servo’ corrects for internal electronic drifts, and a ‘ground level signal overcomes the difficulty of maintaining high impedance between connector pins located in the landing gear environment.
The system is calibrated after installation or replacement of a gear. Readjustment of calibration is not required during normal operation of the aircraft.
Versatile features of the system include the ability to observe weight on each individual gear, corrections for several loading configurations, a load planning device, and a complete self test of the system.