Frenet-Based Algorithm for Trajectory Prediction

An algorithm for aircraft trajectory prediction is presented that is based on two algebraic representations of the aircraft c.g. trajectory in the Frenet frame: (1) a cylindrical helix, during steady flight segments, and (2) a third-order accurate expansion, during transient maneuvering phases. This technique allows for an efficient evaluation of future c.g. positions in a time interval the extension of which depends on the aircraft maneuver state, without requiring the implementation of the aircraft dynamic model. A Kalman filtering technique with a fixed-lag smoother is used for simultaneously filtering the sensor noise and estimating accelerometer and rate-gyro signal derivatives. The effect of a step variation of commanded load factor and/or roll angle on the aircraft position at following times is displayed to the pilot as a visual aid for representing achievable future positions during the maneuver. The algorithm is demonstrated by computer simulation of reverse turn maneuvers of an F-16 fighter aircraft model.