This paper presents the development and flight test evaluation of a reactionary envelope protection method suitable for limit protection in uninhabited aerial vehicles (UAVs). The method is based on finite-time horizon predictions of limit parameter response for detecting any impending limit boundary violations. Limit violations are prevented by treating limit boundaries as obstacles and by correcting nominal control/command inputs to track safe-response profiles of limit parameters near the limit boundaries. The method is first evaluated in simulations using the Georgia Tech UAV simulation tool (GUST) for the load factor limit protection. The load factor limit protection system is then evaluated using flight tests on the Georgia Tech unmanned rotorcraft vehicle (GTMax UAV) at Georgia Tech. The flight test results show that the reactionary load factor limit protection system is successful at maintaining the vehicle load factor response within prescribed upper limit while executing an aggressive e-turn maneuver.