Estimation of aircraft centre of gravity using Kalman filters

The centre of gravity (cg) of an aircraft is of fundamental importance to its stability, but it is difficult to measure precisely in-flight because it will vary as the aircraft manouevres and fuel is consumed and sloshes in its tanks. This paper describes the development of a longitudinal cg estimator using Kalman filters. Two examples are provided of the estimator. The first example uses a linear Phantom F4-C aircraft model in which an unexpected moment representing a cg change is injected into the aircraft and then estimated, and the second example uses a linearised version of a more comprehensive aircraft model, ADMIRE.