The performance after power failure of a helicopter with blade pitch control Parts I and II

Abstract

In Part I a review is made of helicopter performance after engine failure. The transition from powered operation to autorotation is discussed and a theoretical analysis of the motion is given for a single-rotor helicopter with blade-pitch control. The technique of landing from a steady autorotative glide is dealt with briefly; the possibility is indicated of making a safe landing before the transition to steady autorotation has been completed. Reference is also made to the case of engine failure so near the ground that a safe landing may be made by increasing the blade pitch to make immediate use of the rotor energy. In Part II, tests made to investigate the performance of a Hoverfly I in the transition to autorotation following power cut in level flight are described; particular attention is given to the minimum rotor speed attained and to the height lost during the transition. Tests were made to investigate the performance for immediate reduction of pitch only; the need for quick pitch reduction however is stressed because of the rapid fall-off in rotor speed following powercut at high pitch.