Outer-Loop Development and DVE Flight Test Assessment of a Partial Authority Model-Following Control System for the UH-60

The vast majority of the U.S. Army's helicopter fleet consists of aircraft initially developed in the 1960s and 1970s and which were designed based on the handling qualities and flight control requirements of the time for flight in good visual environments (GVE). The Army today uses helicopters at night and in brownout and other degraded visual environment (DVE) conditions but with the same control laws of the original models; the major exception being the CH-47F and MH-47G DAFCS, which have been highlighted as a successful partial authority flight control system upgrade to provide improved handling qualities. The U.S. Army Aviation Development Directorate–AFDD has partnered with the U.S. Army Utility Helicopter Program Office's Futures Team and the RDECOM DVE Mitigation Program to further develop and test the UH-60 Modernized Control Laws (MCLAWS). Previous work implemented a model following control system architecture which provided an attitude command/attitude hold response-type for hover and low speed flight. This system demonstrated improved handling qualities as compared to the UH-60L SAS/FPS rate command response-type. This paper documents work to integrate an outer-loop position hold with velocity command mode into the MCLAWS. Flight testing of the MCLAWS with position hold demonstrated Level 1 Cooper-Harper handling qualities ratings in simulated DVE conditions. Finally, landing logic has been integrated into the MCLAWS to support DVE landing flight testing.