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美国政府科技报告
>FLIGHT INVESTIGATION OF EFFECTS OF ROTOR-BLADE TWIST ON HELICOPTER PERFORMANCE IN THE HIGH-SPEED AND VERTICAL-AUTOROTATIVE -DESCENT CONDITIONS
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FLIGHT INVESTIGATION OF EFFECTS OF ROTOR-BLADE TWIST ON HELICOPTER PERFORMANCE IN THE HIGH-SPEED AND VERTICAL-AUTOROTATIVE -DESCENT CONDITIONS
Flight—performance measurements were made on an untwisted, plywoodcovered rotor in the high-speed and vertical-authoritative-descent conditions. The results were compared with measurements on a similar rotor having 8° of linear washout and with theoretical calculations in order to determine the effects of rotor—blade twist on helicopter performance.nThe use of negative "blade twist appears to be an effective means for increasing the maximum speed of the helicopter as limited by blade stall and for reducing the performance losses due to stall at a given thrust coefficient and tip—speed ratio. In particular, an increase of approximately 7 miles per hour or about 10 percent in the limiting forward speed of the helicopter seems possible with the use of -8° twist. In terms of profile-drag power savings at a given airspeed, once stalling had developed on both rotors, the rotor profile-drag losses incurred by blade stall could be reduced by approximately 40 percent of the average profile-drag power absorbed by the rotors in the unstapled condition by use of -8° twist.
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