FAA Private Pilot Helicopter (PRH)Helicopter Aerodynamics and SystemsEasy
A student pilot asks how moving the cyclic stick changes the pitch angle of each main rotor blade individually as the rotor turns. The flight instructor explains that this mechanical linkage between the stationary fuselage and the rotating rotor system is accomplished by the:
- Alead-lag hinge, which allows the blade to move fore and aft in the plane of rotation
- Bswashplate assembly, which tilts or rises/lowers to vary blade pitch cyclically and collectively
- Ctail rotor pitch change mechanism, which is linked to the anti-torque pedals
- Dfreewheeling unit, which disconnects the engine from the rotor system
Show answer & explanationAnswer & explanation
Correct answer: B. swashplate assembly, which tilts or rises/lowers to vary blade pitch cyclically and collectively
The swashplate consists of a stationary and a rotating ring connected by pitch links to the blade grips; tilting the swashplate produces cyclic pitch changes and moving it up/down produces collective pitch changes.
Why the other options are wrong
- A. The lead-lag hinge relieves Coriolis-induced stresses, not pitch changes.
- C. Tail rotor pitch is a separate system operated by pedals, not related to cyclic linkage.
- D. The freewheeling unit allows the rotor to continue turning if the engine stops; it does not control blade pitch.
Swashplate Assembly
A mechanical device consisting of stationary and rotating rings that transfers cyclic and collective control inputs from the non-rotating airframe to the rotating rotor blades.
- Tilting the swashplate changes blade pitch cyclically (once per revolution)
- Raising/lowering the swashplate changes collective pitch (all blades equally)
- Connected to blade grips via pitch links
- Essential link between pilot controls and rotor system
Memory trick: Swashplate 'swashes' pilot commands up to the spinning blades.