A series of wind tunnel tests and analytical studies were performed on a 1/6-Froude-scale model of the RAH-66 Comanche bearingless main rotor system at the Boeing V/STOL Wind Tunnel. The primary focus was the aeromechanical stability characteristics of the rotor-fuselage system. A secondary focus was correlation of analytical stability predictions with measured results, so that the methodologies could be used with confidence for the full-scale aircraft. An initial test with elastomeric dampers unvovered a limit cycle instability. It was determined that the nonlinear stiffness and damping characteristics of the elastomeric damper, combined with the low roll inertia of the Comanche aircraft, was the fundamental cause of the instability. To solve this limit cycle problem, Fluidlastic (registered trademark Ford Corp.) lead-lag dampers, which provide increased damping and a more constant stiffness, were incorporated in the Froude-scale model. A second test entry was used to verify that the Fluidlastic lead-lag dampers eliminated the limit cycle instability and to clear the prototype aircraft for first flight. Overall, analytical correlation with the test data was very good for both hover and forward flight.
Aeroelastic stability Wind Tunnel testing with analytical correlation of the Comanche bearingless main rotor
Windkanalversuche mit analytischer Korrelation der aeroelastischen Stabilitätswerte für den lagerlosen Hauptrotor des 'Comanche'
Journal of the American Helicopter Society ; 42 , 3 ; 207-217
1997
11 Seiten, 19 Bilder, 1 Tabelle, 19 Quellen
Article (Journal)
English
Rotor (Drehflügel) , Hubschrauber , Vergleichsmessung , Windkanal , Modellversuch , Stabilität , Froude-Zahl , Aerodynamik , Flugzeugrumpf , Korrelation , Rechenmodell , Instabilität , Trägheitsmoment , Steifigkeit , Schwingungsdämpfer , Prototyp , Schweben , Welle-Nabe-Verbindung , Resonanzfrequenz
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