ONTROLLABILITY and stabilizability are very important properties of any controlled system. They convey the idea of timely control of states of a system along desired trajectories in the state space. For completeness the state space should not only include aircraft internal states but also interactions between aircraft and the surrounding environment. Such inclusions make the aircraft’s physics based model to be a much more realistic representation of actual aircraft. Physics based models with such states can be used in determination of controllability of aircraft in real-time. In principle, no controller, either human or automatic algorithms, is capable of controlling an uncontrollable system, so in this work, the concept of loss-of-control does not imply loss of the controllability condition but the incapacity of a pilot to find a control solution to recover the aircraft form upset potentially dangerous conditions. Vehicle upsets included abnormal attitude, stall, uncontrollable descent, abnormal angular rates and airspeed.

A number of Studies have been done to increase the understanding of aircraft loss-of-control (LOC). Using an optimal control formulation Ref.[1-2] calculated the reachability of a subset of the states for a specified time horizon, out of which the aircraft will inevitably leave the safe maneuvering envelope. Ref [3-4] analyzed the bifurcation phenomenon associated to stall, spin and other upset scenarios, and its impact in loss of maneuverability and difficulty to regulate the aircraft close to a bifurcation point. Ref.[3] proposed a design of a high order sliding