Balancing CH-53K Handling Qualities and Stability Margin Requirements in the Presence of Heavy External Loads

The CH-53K Program is planned to include a full authority Fly-By-Wire (FBW) flight control system with advanced control laws and task tailored response types. The control laws will place a special emphasis on low-speed operations and operations with slung loads. The control laws will include response types such as Rate Command Attitude Hold (RCAH) and Attitude Command Velocity Hold (ACVH) and other specialized modes for specific operations. These modes are designed to minimize pilot workload while maximizing the ability of the aircraft to maneuver predictably and precisely. The large size, and the slow rotor RPM of the CH-53K, however, makes achieving these goals more difficult. The paper shows that there is a direct conflict between stability margin requirements and handling qualities improvements that are achievable, especially in the context of a large helicopter with advanced response types that is required to carry large external loads. The paper also explores the limits of such a configuration and suggests an approach to trading-off the constraints so as to produce a design that meets customer requirements.