Types of Rotor Systems


Describe the 3 blade movements, and describe the 3+ different types of rotor systems.


  1. Blade forces and movements
  2. Types of rotor systems
  3. Other rotor systems

Instructional aids

None specified


Blade forces and movements
  • Feathering is rotation of the blade along its long axis, and allows the blade pitch to change. Changing the collective setting or making cyclic inputs changes feathering.
  • Flapping is the vertical movement of the blade in its plane of rotation. Flapping occurs because of differences in lift between the advancing and retreating blades.
  • Lead-lag (also called hunting) is the fore-aft movement of the blade in its plane of rotation. Acceleration forces on the blade cause lead-lag movements.
Types of rotor systems
  • Rigid rotor systems
    • Only utilize a feathering hinge
    • Lead-lag and flapping forces are absorbed by the rotor hub
  • Semi-rigid rotor systems
    • 2-blade rotor systems
    • Has a feathering hinge
    • Main rotor hub tilts (or teeters) to allow for flapping: as one blade flaps up, the other flaps down
    • Lead-lag forces are absorbed by blade flex
  • Fully-articulated rotor systems
    • 3+ blade rotor systems
    • Has feathering and flapping hinges
    • Lead-lag hinges on each blade
Other rotor systems
  • Will be covered in detail in anti-torque systems
  • Tandem, in-line main rotor systems (eg, Chinook), sychropter (K-MAX), coaxial (KA-50/KA-52)

Real-life advice and experience

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Additional resources

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