The stability of an isolated hingeless rotor in forward flight is investigated, both experimentally and analytically. The test model has four soft-inplane and torsionally soft blades, and is tested at realistic tip speeds. The collective pitch and shaft angle are set prior to each test point, and the rotor is trimmed as follows: the longitudinal and lateral cyclic pitch controls are adjusted through a swashplate to minimize the 1/rev flapping moment at the 12 % radial station. Key measurements in the database include the cyclic pitch controls, steady root-flap moment and lag regressive-mode damping for two coning angles with advance ratio, shaft angle and collective pitch variations. A modal approach, the ONERA dynamic stall models of lift, drag and pitching moment, and a three-dimensional state-space wake model are used. The cyclic pitch controls and the corresponding periodic responses are predicted by the periodic shooting method with damped Newton iteration; this method is based on the fast-Floquet theory and generates the equivalent Floquet transition matrix (EFTM) as a byproduct. The eigenvalues and eigenvectors of the EFTM lead to the frequencies and damping levels. All the structural and aerodynamic states are included from trim analysis to eigenanalysis. A major finding is that dynamic wake dramatically improves the correlation of the lateral cyclic pitch control.
A theoretical and experimental investigation of hingeless-rotor stability and trim
Theoretische und experimentelle Untersuchung der Stabilität und Trimmung von schwenkgelenklosen Rotoren
European Rotorcraft Forum, 23 ; 1 ; 10-15
1997
15 Seiten, 14 Bilder, 3 Tabellen, 19 Quellen
Conference paper
English
Hubschrauber , Rotor (Drehflügel) , Gelenk (Technik) , Stabilität , theoretische Untersuchung , experimentelle Untersuchung , Umfangsgeschwindigkeit , Winkel (Geometrie) , Taumelscheibentrieb , Schwungmoment , Datenbasis , Abreißen der Strömung , Modell , Newton-Zahl , Iteration , Matrix (Zahlenschema) , Eigenwert
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