Onboard Aircraft Weight and Balance System

A method for determining the weight and balance of an aircraft having a plurality of landing gear, each including a shock strut, the method comprising:

• installing an onboard system for determining the weight and balance of the aircraft aboard the aircraft, the system including:
• a memory storing calibration data comprising breakout friction data of respective ones of the shock struts of each of the landing gears, the stored calibration data including a plurality of successive constant breakout pressures of each strut observed during a calibration loading and unloading of the aircraft and a plurality of breakout friction forces associated with respective ones of the breakout pressures and computed as a function of the respective breakout pressures and an actual load acting on the strut during the calibration loading and unloading;
• pressure sensors for sensing the pressures in respective ones of the landing gear shock struts during a subsequent loading or unloading of the aircraft;
• load sensors for sensing the vertical loads exerted by respective ones of the landing gear on the aircraft during the subsequent loading or unloading thereof;
• an attitude sensor for sensing the attitude of the aircraft relative to the horizontal during the subsequent loading or unloading thereof;
• and,
• a computer operable to compute the actual vertical load Lv acting in each of the landing gears during the subsequent loading or unloading from the calibration shock strut breakout friction data stored in the memory, the shock strut pressures sensed with the pressure sensors, landing gear unsprung loads, landing gear loads sensed with the load sensors and attitude of the aircraft sensed with the attitude sensor.

A method for determining the weight and balance of an aircraft, the method comprising:

• using a pressure sensor to sense a breakout friction force acting in a landing gear shock strut of the aircraft during a loading or unloading of the aircraft;
• computing a load acting in the landing gear as a result of the breakout friction force sensed;
• using a load sensor to sense the loads exerted on the aircraft by the landing gear during the loading and unloading;
• and,
• using the load sensed by the load sensor to correct the computed load acting in the landing gear.