ABSTRACT
Frequently involve advanced vision aids such as night vision goggles, forward looking infrared or millimetric waveband radar presented to the pilot via helmet-mounted device or instrument panel. Main blades turn at set RPM creating relative wind over airfoils; generates total rotor thrust and lift. Torque effect of main rotor countered with tail-rotor thrust in the opposite direction, by contra-rotating systems in tandem, or contra-rotating coaxial design. Difference in lift between advancing and retreating half of rotor disk caused by differential velocity at forward speed. Autorotation Controls manoeuvring and arrest rate of descent with engine failure, preserves potential energy and control in rotor system by disengaging from the engine through lowering collective and reducing angle of attack. Noise can exceed 100 dBA in cockpit/cabin of some airframes; varies across frequency spectrum; noise-induced hearing loss of occupational concern. Aircrew equipment needs to be optimized for rotary wing operations.
