Boeing is to test a smart helicopter rotor in a NASA windtunnel to verify the vibration, noise and performance improvements expected in forward flight with in-blade active flaps. The modified MD 900 commercial-helicopter rotor system was tested on a whirl tower in early 2004, demonstrating reduced hover vibration.
Testing of the 10.4m (34ft)-diameter rotor at NASA Ames Research Center's 12 x 24m windtunnel in California will be conducted under a $3 million US Defense Advanced Research Projects Agency contract. The smart-material actuated rotor was built and whirl-tested under a previous DARPA programme.
Each of the rotor's five composite blades has an active trailing-edge flap driven by a piezoelectric actuator and motion amplifier located in the leading edge. The flaps provide high-bandwidth, limited-authority active control of the lift generated by each blade as it rotates. DARPA has previously said the whirl tests demonstrated an oscillatory thrust greater than 10% of the steady baseline thrust.
Boeing says the whirl tower tests validated the authority and robustness of the modified rotor system. Windtunnel tests, due to be completed by the third quarter of 2008, will study the forward flight characteristics and gather data to validate aero-acoustic analysis codes. A flight demonstration would then be required before the technology could be considered for use in the AH-64D, says Boeing.
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Each of the rotor's five blades has an active trailing-edge flap |
Source: Flight International
