Aircraft flight control system and method.

Abstract

Aircraft flight control system and method. The flight control system (10) comprises primary (PRIM1, PRIM2, PRIM3) and secondary (SEC1, SEC2, SEC3) flight control computers. Each secondary computer is configured to: - determine if a situation exists in which no primary computer is functional, said secondary computer receives valid airspeed and inertial information from the aircraft, and said secondary computer has not received a flight command from a flight control device (16) for at least a predetermined duration; - if said situation exists, activate a flight mode in which said secondary computer is configured to: . determine roll and pitch angles based on airspeed and inertial information from the aircraft; .Calculate control commands for control surface actuators connected to this secondary computer in order to maintain the aircraft level and at a constant altitude; and control the control surface actuators (a1a … a1n, a2a … a2p, a3a … a3q) connected to this secondary computer according to the calculated commands. Figure for the abbreviation: Fig. 2.

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