A LOW ALTITUDE CONTROL CONCEPT FOR U.S. ARMY ROTARY WING AIRCRAFT

This paper covers the development of the U.S. Army's applied research project for providing a low-altitude capability for Army rotary-wing aircraft. The overall program goals and objectives are described, followed by a detailed dissertation on the system philosophy and the experimental hardware development necessary for implementing the system. The Terrain Following Radar/Autopilot Coupler constitutes the major element in the control loop of the system. Its development and functions based on the basic control equations of the airframe and the terrain following system are discussed in detail, including the simulation studies performed for parameter selection and optimization. A unique method of in-flight simulation of the terrain and radar sensor allows full in-flight evaluation of a control system and offers unlimited flexibility as to the type of terrain over which the system is to be tested without subjecting the aircraft to the hazards of testing a control system in close proximity to terrain. The terrain and radar simulator and its functions are discussed. A variable parameter radar is briefly described which will replace the terrain and radar simulator upon completion of the in-flight analysis and evaluation of the control system. Finally, the flight test plan is briefly discussed showing the test flexibility offered through the use of the terrain and radar simulator.