Multivariable Flight Control for an Attack Helicopter

This paper will discuss advanced flight control laws for the Apache YAH-64 helicopter. The control laws have been succesfully flight tested and were extensively evaluated with fixed base piloted simulation as part of the Advanced Rotorcraft Technology Integration Flight Experiment The control laws employ three body rate gyros, and normal and lateral accelerometers as sensors and collective, tail rotor, and lateral and longitudinal cyclic controls. The control laws were developed to provide decoupling, gust attenuation, desensitization, and stability augmentation in the face of aircraft modelling uncertainty. A multivariable proportional plus integral element is the basic ingredient of the control laws. Various analyses including frequency and time responses will be presented. Stability robustness properties of the control laws will be presented using singular value and structured singular value techniques. Responses of the controlled helicopter to pilot and gust inputs will be presented using time histories.