Integrated Trailing-Edge Flaps and Servotabs for Helicopter Primary Control

摘要

A swashplateless rotor has the potential to reduce the aircraft empty weight, rotor drag, and control power requirement in forward flight, in addition to providing individual blade control capability for vibration reduction and noise mitigation. The focus of the present paper is on primary control using a servotab actuated trailing edge flap system to control blade pitch. First, concept feasibility is established through wind tunnel testing of a nonrotating wing section. Next, a rigid blade aeroelastic trim analysis is carried out in forward flight for a Kaman-type conceptual rotor with very low blade torsional stiffness. A parametric sensitivity study determined an optimized design space that simultaneously reduces tab deflections and hinge moments. Finally, the flap and tab dynamics are modeled within a comprehensive analysis that includes the inertial and aerodynamic contributions of the flap and the tab, blade flexibility, a two-dimensional unsteady aerodynamic .model, and free wake. A UH-60A type helicopter at 155 kt (μ = 0.368) and 17,500-lb thrust (c_T/σ = 0.084), and tab-actuated trailing edge flaps with 22% flap chord and 13% tab chord, is trimmed using tab deflections within ±5°, and mean tab hinge moment less than 3 ft-lb.