Development and Concept Demonstration of a Physics Based Adaptive Flight Envelope Protection Algorithm*

This paper discusses the development of an adaptive protection algorithm which is based on a physical approach, with the purpose to keep a closed loop aircraft with manual control laws within the actual safe flight envelope, even in the presence of failures or disturbances. Adaptive estimation of the flight envelope guarantees that not only flap changes, but also damage (e.g. icing) and external disturbances such as wind can be taken into account. This method is robust with respect to uncertainties in the estimates for the aerodynamic properties. This updated information is used in the flight control laws to prevent loss of control in flight. This development can extend the functional envelope of the nominal law and reduce the need to switch from nominal to alternate law in the presence of certain failures. This algorithm has been applied on a fairly matched A320-type of simulation model and the setup has been implemented in the DLR Robotic Motion Simulator at the German Aerospace Center as a concept demonstrator.