UNCLASSIFIED 15s. DECLASSIFICATIONO,'OWNGRADING SCHEDULE 16 DISTRIBL-TION STATEMENT (of tlits Report) APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED ýý,DISTRIBUTiON ST ATEMENT (of the eb*.Iract enereed in Block 20, If different from Report) 18Ii. SUPPLEMEN-ARY NOTES 119 K(EY WOPOS (Conlinue on reverse side ?I neceessary end identify by block number) IPRELIMINARY ARMY EVALUATION HOVER PERFORMANCE CH-47C HELICOPTER LEVEL FLIGHT PERFORMANCE FIBERGLASS ROTOR BLADE HANDLING QUALITIES 2[0. APST PACT (Con tinue on reverse side If nece,-sary end Identify by block number) ýAPreliminary Army E~valuation of a CH-47C helicopter equipped with Fiber~1ass roor blades was flown from 31 October through 7 November 1978. A total of FE ^4 hour, 1-of which were productive, was required. Tests were conducted at the Boeing Vertol test facility at Wilmington, Delaware. Fiberglass rotor bladcýs at ã rotor speed of 225 rpm have improved hover performance in terms of decretased power required when compared to metal blades at the operating rotor speeds of 235 and 245 rpm. Tlhere is an improvement in level flight performance in terms of a-FORM 1/ DTOUCASFE U~i 1AN 73 EION OF I NOV 65 IS OBSOLETE WISECURITY CLASSIFIAIN07',I PAGE (Whien Daet Entered) IINCT ASTFIFTED SECURITY CLASSIFICATION OF THIS PAGE(When Daot Entormd) 20. ABSTRACT reduction in power required between fiberglass blades at a rotor speed of 225 rpncompared 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 Lados and were associated with excessive cabin noise levels, lack of adequate intercom/radio audio gain when using earplugs and poor power management characteristics. The cruise guide indicator (CGI) provides useful information to the pilot for recogwizing and recovering from the effects of aft rotor stall. Engine start sequence and sw~tchology were in proved.\
•'• ''-• signtificantly improved over the OH-58A. Performance in terms of power required and fuel flow is slightly degraded when compared to the OH-58A at similar gross weights and altitudes and in general did not meet the estimates of the detail specification for the OH-58C. The handling qualities and vibrations of the OH-58C are similar to the OH-58A when operating at similar gross weights and altitudes. MThe lvmdling qualities deficiencies relative to the low speed flight characteristics were identified. e inadequate directional control; the tendency for the aircraft to pitch and yaw excesivel in rearward flight. These lead to the overall conclusion of unsatisfactory low speed flight hacteristics. Another handling qualities deficiency was an aperiodic pitch divergence. ard flight climbs at rates of climb above 1000 ft/min. This deficiency was corre • en the engine infrared exhaust stacks were replaced with standard exhaust stacks. A _btn.ian factors evaluation of the cockpit revealed one deficiency (the night vision goggle switch is easily adtivited and renders the caution/advisory panel unreadable), and fourteen shortcomings. Two maintenance deficiencies were also noted: an easily clogged transmission oil cooler system and an uncommanded disconnect of the primary directional control system during right sideward flight. A total of sewvn deficiencies and 23 shortcomings were identified. The low speed flying qualities deficiancies were observed in the OH-58A. but increased in severity due to the higher gross weight, higher altitude capability and primary mission change to Nap-of-the-Earth flight for the OH-58C. The easily clogged transmission oil cooler deficiency is common to both the OH-58A and C. The other three deficiencies are caused by OH-58C aircraft changes. Of the 23 shortcomings, 10 were attributed to the OH-58C modification and 12 shortcomings are common to both the OH-58A and C. ,I 'V *SCuflVv CLASSIFICATION OF THIS PACE(Osen Dee. Znteh* W i DEPARTMENT OF THE ARMY 6 NO, US ARMY AVIATION RESEARCH AND DEVELOPMENT COMMAND
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