Design and Flight Test of a Cable Angle Feedback Control System for Improving Helicopter Slung Load Operations at Low Speed

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. This dissertation investigates the dynamics, handling qualities requirements, and control aspects of the helicopter/slung load system that contribute to the performance of piloted slung load operations. A control system is developed that integrates measurements of both slung load motions and conventional fuselage feedback to improve the handling qualities for hover/low speed operations. Despite the fact that this technology was developed 40 years ago, it has not been tested in a manned helicopter since the 1970s, due to problems with handling qualities and pilot perception. This dissertation leverages advances in flyby- wire, complex control design procedures (direct multi-objective optimization), and recently developed work that relates handling qualities to dynamic response (specifications) to successfully flight test cable angle feedback technology in a manned helicopter. The key contributions of this work are developing an understanding of the handling qualities trade-offs for cable angle/rate control system design, implementing an approach to solve the problem with a novel task-tailored control system, and performing extensive piloted flight tests of the control system on a fly-by-wire Black Hawk. The flight tests demonstrated that average precision load set-down time was reduced by 50% for a light load, 30% for a heavy load, and the average handling qualities rating for the external load placement task was improved from Level 2 to Level 1 on the Cooper-Harper rating scale, a significant improvement.
The original document contains color images.