Definition
A two-bladed helicopter main rotor system in which both blades are rigidly attached to a common hub, and the hub is mounted on a single horizontal hinge (the teeter hinge) that allows the entire blade pair to rock as a unit. As one blade flaps up, the other flaps down, like a child's seesaw. Also called a teetering rotor or semi-rigid rotor.
Plain English
A helicopter rotor with two blades joined together so they tilt as one piece — when one side rises, the other side drops, the same way a seesaw works.
Context Anchor
Seen in helicopter systems, especially when describing two-blade semi-rigid rotor designs.
Derivation
Named directly after the playground seesaw, because the two blades pivot about a central point and rock up and down opposite each other in exactly the same motion.
Why Pilots Care
This design affects stability, control response, and the need for specific rotor head components like droop stops during ground operations.
Analogy
Imagine a playground seesaw: push one end down and the other end rises, exactly the way the two blades move together on the hinge.
Intuition Check
Do not read “seesaw” as a separate part of the helicopter. Here it describes the rocking motion of the two-blade rotor system.
Example Sentence 1
The Robinson R22 uses a seesaw rotor, so the pilot must avoid low-G conditions to prevent mast bumping.
Example Sentence 2
During preflight the student checked the teetering hinge area of the seesaw rotor for proper lubrication.