Validation and application of a transient aeroelastic analysis for shipboard engage/disengage operations

A recently developed transient aeroelastic rotor response analysis is used to investigate shipboard rotor engage/disengage sequences. The blade is modeled as an elastic beam undergoing flap and torsion deflections and the equations of motion are discretized using the finite element method. The discretized equations of motion are integrated for a specified rotor speed run-up or run-down profile. Blade element theory is used to calculate quasi-steady or unsteady aerodynamic loads in linear and nonlinear regimes. Three deterministic wind gust distributions are used to model the ship airwake environment. This analysis is modified to include a flap stop which restrains upper flap motion and a flap damper which damps flap hinge motion. Validation studies are conducted using experimental data collected from a ship/helicopter model placed in a wind tunnel. Theoretical predictions show good agreement with experimental data for windward hub locations on the deck. A study to evaluate the effectiveness of a flap damper placed at the flap hinge is conducted. Results indicate that a flap damper is an effective method to reduce downward tip deflections for an H-46 if the flap stop angle is raised. The H-46 throttle advancement rate is also shown to reduce the maximum downward tip deflections for spatially varying gusts.