CH-53E Digital Automatic Flight Control System

The U. S. Navy has recently authorized Sikorsky to proceed with production incorporation of the Digital Automatic Flight Control System in the CH-53E Super Stallion. Being the first digital automatic flight control system in a production helicopter, the CH-53E system represents the threshold of a new flight controls era and state-of-the-art advancement. The digital system replaces the automatic flight control system in earlier CH-53 models which utilized conventional analog type circuitry. Reliability, maintainability, flexibility, future growth and cost improvements made the digital system a choice over the conventional analog automatic flight control system. The digital system has undergone unprecedented reliability evaluation and testing during its development. Conventional inner loop stabilization, hover augmentation, force feel, and outer loop stabilization are all provided digitally by the new system. This paper addresses Sikorsky's experience in developing and testing the new digital system. A description of the design is given in terms of both hardware and software. This description includes discussions of the system's hardware and software structure, redundancy management scheme, and self-test features. The validation of the design in flight, and in formal reliability tests, is discussed together with the results achieved.