Design and Flight Test of a Cable Angle Feedback Flight Control System for the RASCAL JUH-60 Helicopter

Abstract

The ability of a helicopter to carry externally slung loads makes it very versatile for many civil and military operations. However, the piloted handling qualities of the helicopter are degraded by the presence of the slung load. A control system is developed that uses measurements of the slung load motions as well as conventional fuselage feedback to improve the handling qualities for hover/low-speed operations. Prior research has shown a fundamental trade-off between load damping and piloted handling qualities for a feedback control system with cable angle/rate feedback. A new task-tailored approach proposed and implemented herein uses a method of switching between a load damping mode and a piloted handling qualities mode. These modes provide appropriate load feedback depending on the piloting task and flight regime. This provides improved handling qualities for maneuvering flight and for improved precision load control at hover. A new mission task element for precision load placement is developed (for possible inclusion into ADS-33E-PRF) to test the ability of the cable feedback system to improve load placement task performance. The improvements provided by this control system are demonstrated in a piloted flight test on the JUH-60A RASCAL fly-by-wire helicopter. The average load set-down time was reduced by a factor of two for the 1000-lb load on a 56-ft sling.