Rotorcraft Vocabulary Flashcards

These flashcards cover key vocabulary terms and definitions related to rotorcraft systems and mechanics.

Fully Articulated Rotor System

Rotor system that allows blades to flap, lead/lag, and change pitch independently. Each blade has hinges and dampers to accommodate motion and reduce stress.

Semi-Rigid Rotor System

Rotor system that allows for pitch change and flapping via a teetering hinge. Does not support independent lead/lag movement.

Rigid Rotor System

Rotor system with no hinges; relies on blade flexing (composite materials) to accommodate flapping and lead/lag. Simplifies mechanical parts and improves responsiveness.

Blade Flapping

Up and down motion of rotor blades to compensate for dissymmetry of lift during forward flight.

Lead-Lag (Hunting)

Forward and backward movement of blades in the plane of rotation to balance changes in rotor speed and loading.

Dissymmetry of Lift

Uneven lift created due to different relative wind speeds on advancing and retreating blades. Compensated by blade flapping and cyclic input.

Coriolis Effect (Rotorcraft)

Change in rotational speed caused by movement of blades closer or farther from the axis. Managed with lead-lag hinges.

Conservation of Angular Momentum

Rotor RPM changes with blade movement in aggressive maneuvers. Engine control units adjust fuel to compensate.

Gyroscopic Precession

Force applied to a rotating system manifests 90 degrees later in the direction of rotation. Used in cyclic control response.

Cyclic Pitch Control

Changes pitch of rotor blades cyclically to control directional movement (forward, back, left, right).

Collective Pitch Control

Changes pitch of all blades simultaneously to control altitude (up and down movement).

Anti-Torque Pedals

Control tail rotor thrust to manage yaw and keep helicopter pointed in the desired direction.

Tail Rotor

Conventional anti-torque system using a small rotor at the tail to counteract torque from the main rotor.

Fenestron

Enclosed tail rotor system that improves safety and noise reduction. Also called a 'fan-in-fin' system.

NOTAR

No Tail Rotor system that uses a ducted fan and Coand effect to provide anti-torque thrust via differential air pressure.

Autorotation

Flight condition where the main rotor is driven by upward airflow instead of engine power, used in engine failure situations.

Dynamically Unstable

Helicopters require constant pilot input to maintain stable flight. Letting go of controls can lead to loss of control.

Pitch Horn

Component that links control rods to the blade for pitch changes.

Teetering Hinge

Mechanism in semi-rigid rotors that allows blades to seesaw in opposite directions to balance lift.

Torque

Rotational force produced by the engine. Without counteraction, it causes the fuselage to spin opposite to rotor direction.