Accession Number : AD0255927

Title :   EVALUATION OF THE VERTOL STABILITY AUGMENTATION SYSTEM AND DIFFERENTIAL DELTA-3 IN AN H-21D

Corporate Author : AIR FORCE FLIGHT TEST CENTER EDWARDS AFB CALIF

Personal Author(s) : PUTNAM,V. KEITH ; FERRY,ROBERT G.

Report Date : MAY 1959

Pagination or Media Count : 1

Abstract : An H-21D helicopter with the Vertol stability augmentation system (SAS) and differential-deltathree was evaluated. The differential-deltathree was found to provide acceptable longitudinal dynamic stability and allow hands-off flight (longitudinally) for periods of up to 1 minute. The longitudinal channel of the SAS also provided positive longitudinal stability and allowed hands-off flight for periods of at least 1 minute. With the SAS operating, the response to a longitudinal disturbance was (jerky) and was considered objectionable in rough air. It must be noted that the differential-delta-three was operating at all times and therefore a double correction for longitudinal disturbances was present with the SAS operating. The lateral stability provided by the SAS was considered excellent. However, the reduction in lateral control response and the nature of the response (a 1 inch step input results in a fixed bank angle and does not maintain a roll rate) with SAS operating were objectionable. The SAS did not improve directional flying qualities, and some loss of directional control response was noted in hover. (Author)

Descriptors :   *HELICOPTERS, *ROLL, *STABILIZATION, CONTROL SYSTEMS, DAMPING, FLIGHT TESTING, GYROSCOPES, HELICOPTER ROTORS, PITCH (MATERIAL), PITCH (MOTION), ROTOR BLADES (ROTARY WINGS), ROTOR BLADES (TURBOMACHINERY), YAW

Distribution Statement : APPROVED FOR PUBLIC RELEASE