Preliminary Airworthiness Evaluation CH-47C with Fiberglass Rotor Blades (with T55-L-712Engines).

摘要

A Preliminary Army Evaluation of a CH-47C helicopter equipped with Fiberglass rotor blades was flown from 31 October through 7 November 1978. A total of 22 hours, 13 of which were productive, was required. Tests were conducted at the Boeing Vertol test facility at Wilmington, Delaware. Fiberglass rotor blades at a rotor speed of 225 rpm have improved hover performance in terms of decreased power required when compared to metal blades at the operating rotor speeds of 235 and 245 rpm. There is an improvement in level flight performance in terms of a reduction in power required between fiberglass blades at a rotor speed of 225 rpm compared to metal blades at a rotor speed of 245 rpm. Handling qualities, for all conditions tested, were essentially the same as with metal rotor blades and are satisfactory. Five shortcomings were identified, only two of which were related to the fiberglass rotor blades. The fiberglass blade related shortcomings were (1) the high six-per-rotor-revolution (6/rev) (22.5 Hz) vibration levels in the vicinity of the cargo hatch and ramp area at light gross weight and airspeeds of 100 knots calibrated airspeed (KCAS) and above; and (2) high vibration levels (3 and 6/rev) throughout the aircraft at airspeeds of 140 KCAS and above. The other shortcomings are standard CH-47C problems that remain unchanged with fiberglass rotor blades and were associated with excessive cabin noise levels, lack of adequate intercom/radio audio gain when using earplugs and poor power management characteristics.