the takeoff weight of an aircraft is computed from measures of the thrust of the engines and the forward acceleration of the aircraft detected over a time period when such acceleration is at a maximum following brake release on the runway . a major variable that must be considered is the coefficient of rolling friction of the landing gear of the particular aircraft involved and other factors inducing ground roll drag . the present invention calculated this variable as a function of engine thrust and manifest weight for each takeoff of the aircraft and updates weighted filter values thereof for use during subsequent takeoffs . for each takeoff , therefore , and average value of rolling friction is used to calculate takeoff weight , which average value becomes more nearly the actual value for the existing condition of the landing gear .