Helicopter Aerodynamics

8 Hours Types, mechanisms, characteristics, and working principles of helicopters. Theory of rotary-wing flight. Key terminology. Effects of gyroscopic precession, torque reaction and directional control, dissymmetry of lift, blade tip stall, translating tendency and its correction, Coriolis effect and compensation, vortex ring state, and power settling.

8 Hours Blade forces and motion in forward flight. Force, torque, and flapping coefficients. Helicopter trim and performance analysis in forward flight. Transmission systems: gearboxes, main and tail rotors, clutches, freewheeling units, rotor brakes, tail rotor drive shafts, flexible couplings, bearings, vibration dampers, and bearing hangers.

8 Hours Airworthiness requirements for structural strength. Structural classification: primary, secondary, and tertiary structures. Fail-safe, safe-life, and damage-tolerance concepts. Zonal and station identification systems. Basic structural loads: stress, strain, bending, compression, shear, torsion, tension, hoop stress, and fatigue. Provisions for drainage and ventilation.

8 Hours Momentum and blade element theories. Blade advance ratio, figure of merit, profile and induced power estimation. Constant chord and ideal twist rotors, over-pitching, autorotation, and ground effect. Tip loss factor and Prandtl’s tip loss correction. Effects of compressibility on rotor blades. Aerodynamic interference between main rotor and tail rotor. Effect of blade aspect ratio and blade solidity on performance. Power required in different flight conditions (hover, forward flight, climb).

8 Hours Rotor alignment, main and tail rotor tracking. Static and dynamic balancing. Types of vibrations and vibration reduction methods. Ground resonance, helicopter spin, and stall behavior. Flapping, lead-lag, and feathering motions of rotor blades. Dynamic inflow effects on rotor loads. Active and passive vibration control techniques. Blade root moments and load distributions. Flutter and aeroelastic stability considerations in rotor blades.