RECENT ADVANCES IN ROTOR TECHNOLOGY AT BOEING VERTOL

Results of a wind tunnel test on advanced rotor configurations present an assessment of the benefits of advanced airfoils, tip shape, blade chord, and blade number. A CH-47D model rotor with VR-7/8 airfoils was tested as a reference rotor. The advanced rotors, incorporating recently-developed VR-12/15 high speed airfoils, were tested to 231 knots in the wind tunnel and demonstrated an Improvement of 6.0% in figure of merit and 25% in cruise lift-to-effective-drag ratio over a rotor with VR-7/8 airfoils. The advanced airfoils show significant improvements in stall inception limits, flying qualities boundaries and rotor noise. Improved blade tip shapes provide additional benefits in rotor noise and do not reduce the stall inception boundary. These results demonstrate a significant advance in conventional rotor capability, but there are further improvements that can be gained from planform-structural tailoring and further development of airfoils, specifically for high speed rotor operation.