Development and simulation of damage tolerant control laws for a compound helicopter

A piloted simulation study was conducted to evaluate damage tolerant control (DTC) law concepts. The simulated aircraft is a fly-by-wire compound utility helicopter based on the X-49A. The aircraft features auxiliary thrust through a vectored thrust ducted propeller and auxiliary lift through a wing. The configuration includes a number of redundant control surfaces, including flaperons and elevators that help enable DTC. This paper covers the design of the baseline inner-loop control laws, which were optimized to meet Level 1 requirements for a comprehensive set of stability, handling qualities and performance specifications. Methodology and development of the control allocation methods for DTC is presented. The fixed-base piloted simulation experiment qualitatively and quantitatively evaluated the baseline control laws with various control allocation methods. Handling qualities ratings were collected using a series of maneuvers, including pitch and roll capture and tracking tasks. Survivability ratings, quantitative performance metrics, and pilot comments were collected for multiple damage scenarios in which the pilot attempted to safely land the aircraft following damage that severely limited control in one or more axes. Handling qualities ratings were also collected for the tracking tasks in the presence of damage. The paper is concluded with an overall evaluation and comparison of the damage tolerant methods.