Past Applications and Future Potential of Variable Stability Research Helicopters

Variable-stability research helicopters began to be used more than 25 years ago to investigate flying qualities criteria for helicopters. However, their application was soon diverted to investigate mainly the problems of V/STOL aircraft. This emphasis prevailed until the past decade when the greatly increased use of helicopters for a wide variety of more demanding applications resulted in renewed use of these facilities for rotary-wing research. The historical development of variable-stability research helicopters and some of their previous applications are presented as a guide for assessing tneir future potential. The features of three general-purpose rotary-wing flight research aircraft that provide complementary capabilities are described briefly, and a number of future applications are proposed.