FAA Private Pilot Helicopter (PRH)Helicopter Aerodynamics and SystemsEasy
Which type of main rotor system uses hinges that allow each rotor blade to flap, feather, and lead-lag independently of the other blades?
- ATeetering rotor system
- BSemirigid rotor system
- CRigid rotor system
- DFully articulated rotor system
Show answer & explanationAnswer & explanation
Correct answer: D. Fully articulated rotor system
A fully articulated rotor system has separate flapping, feathering, and lead-lag hinges at the blade root, letting each blade move independently to compensate for dissymmetry of lift and Coriolis effect. Semirigid rotors teeter as a unit and rigid rotors have no mechanical hinges.
Why the other options are wrong
- A. Teetering describes the seesaw motion of a two-bladed semirigid rotor, not independent hinging.
- B. Semirigid blades are rigidly attached to the hub but teeter together on a single hinge, not independently.
- C. Rigid systems have no flapping or lead-lag hinges; blade bending accommodates loads.
Fully Articulated Rotor System
A rotor system with separate flapping, feathering, and lead-lag hinges that allow each blade to move independently of the others.
- Usually has three or more blades
- Flapping hinge relieves dissymmetry of lift
- Lead-lag hinge compensates for Coriolis effect
- Feathering hinge changes blade pitch angle
Memory trick: Fully articulated = fully free-moving blades (Feather, Flap, Lag)