A new tiltrotor whirl flutter stability analysis has been developed. The analysis retains the simplicity of a rigid blade model, while still providing accurate results. The formulation is physically motivated-blade flap and lag frequencies are evaluated from first principles, rather than provided as tabular inputs (as in existing simple analyses). Several unique features have been incorporated into the present analysis. First, the distibution of blade flexibility inboard and outboard of the pitch bearing allows proper modeling of variations in flap and lag frequency with collective pitch. Second, separate gimbal and blade flapping degrees of freedom are retained. This physically models the low-frequency (gimbal dominated) cyclic modes and the higher frequency collective mode, and does not require the 'assignment' of different frequencies to the modes. Third, blade torsion dynamics, which have not been considered by existing simple analyses, are modeled. Accounting for the distribution of blade flexibility when formulating the blade pitch equations allows the derivation of closed-form expressions for pitch-lag and pitch-flap coupling parameters. These expressions can be used in lieu of full torsion dynamics. Results from the present analysis are validated against experimental data for several tiltrotor configurations. The analysis generally shows good agreement, both with experimental data and with results obtained from more complex elastic blade analyses. The influence of the various modeling refinements on whirl flutter stability prediction is evaluated and discussed.
Modeling refinements in simple tiltrotor whirl flutter analysis
Verfeinertes Modell zur Beschreibung der Rotorblattschwingungen bei einem Schwenkrotorflugzeug
Journal of the American Helicopter Society ; 48 , 3 ; 186-198
2003
13 Seiten, 27 Bilder, 3 Tabellen, 14 Quellen
Article (Journal)
English
Bewegungsgleichung , Biegeschwingung , Biegesteifigkeit , Dämpfungsfaktor , dynamische Stabilität , Eigenfrequenz , Flatterschwingung , Flügelblatt , Freiheitsgrad , Kardangelenk , Lagersteifigkeit , mathematisches Modell , mechanische Schwingung , Modenkopplung , Rotor (Drehflügel) , Schwingungsmode , Theorie-Experiment-Vergleich , Torsionsschwingung , Transversalschwingung , Schwingungsanalyse
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