AEROELASTIC ANALYSIS OF TRANSIENT BLADE DYNAMICS DURING SHIPBOARD ENGAGE DISENGAGE OPERATIONS/

An analysis has been developed to predict transient aeroelastic rotor response during shipboard engage/disengage sequences. The blade is mod eled as an elastic beam undergoing deflections in flap and torsion. Th e blade equations of motion are formulated using Hamilton's principle and they are spatially discretized using the finite element method. Th e discretized blade equations of motion are integrated for a specified rotor speed run-up or run-down profile. Blade element theory is used to calculate quasisteady or unsteady aerodynamic loads in linear and n onlinear regimes. Three different simple wind-gust distributions are m odeled. Basic ship-roll motion characteristics are also included in th e shipboard airwake environment. An H-46 rotor system model is develop ed and shows excellent correlation with experimental static tip deflec tion and blade natural frequency data; Parametric studies are conducte d-to systematically investigate the effects of collective and cyclic p itch control settings, droop stop angle, and ship motion on blade resp onse. These studies indicate that collective and cyclic control inputs have a moderate effect on maximum negative tip deflections. Torsion i s shown not to be required for rotorcraft with small amounts of pitch- flap coupling. Unsteady aerodynamics is shown only to be important to the blade response-at high wind speeds for spatially varying gusts, A flap damper is incorporated and is effective in reducing tip deflectio ns if the flap stop angle is increased.