Describe the 3 blade movements, and describe the 3+ different types of rotor systems.
- Blade forces and movements
- Types of rotor systems
- Other rotor systems
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