A wind-tunnel investigation of whirl-flutter stability boundaries has been conducted on a 1/5-size semispan tiltrotor model known as the Wing and Rotor Aeroelastic Test system (WRATS) in the NASA-Langley Transonic Dynamics Tunnel as part of a joint NASA/Army/Bell Helicopter Textron, Inc (BHTI) research program. The model was developed by BHTI as part of the JVX (V-22) development program in the 1980s and was modified to incorporate a hydraulically actuated swashplate control system for use in active controls research. The modifications have changed the model's pylon mass properties sufficiently to warrant testing to re-establish its baseline stability boundaries. A parametric investigation of the effect of rotor design variables on stability was also conducted. Experimental baseline stability boundaries in air are presented with comparisons to results from parametric variations of rotor pitch-flap coupling and control system stiffness. Increasing the rotor pitch-flap coupling (delta3 more negative) has a destabilizing effect on stability, while a reduction in control system stiffness has little effect on whirl-flutter stability. The results from tests conducted in R-134a heavy gas indicate that matching full-scale blade Mach number has a destabilizing effect on whirl-flutter. This finding demonstrates that stability boundaries obtained from tests at reduced Mach number in air are unconservative.
A parametric investigation of whirl-flutter stability in the WRATS tiltrotor model
Parametrische Untersuchung der dynamischen Stabilität eines Schwenkrotorhubschraubers am Experimentalmodell
Journal of the American Helicopter Society ; 47 , 2 ; 134-144
2002
11 Seiten, 17 Bilder, 6 Tabellen, 23 Quellen
Article (Journal)
English
A WIND-TUNNEL PARAMETRIC INVESTIGATION OF TILTROTOR WHIRL-FLUTTER STABILITY BOUNDARIES
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