Rotary Flashcards
Define rotor mast
Supports and drives the main rotors
Define rotor disc
Area projected by the rotor travel
Outline Shaft axis
Axis through the rotor mast, which about the rotors are ALLOWED to rotate
Outline axis of rotation
The imaginary line about which the rotars actually rotate
Plane of rotation
Plane at right angles to the axis of rotation
Tip path plane
Imaginary circular plane outline from the rotor tips during travel
Define blade coning
Upward flex of the rotor blades due to pitch and lift increased and centrifugal force is applied
Define cone angle
Angle between blades span wise axis and the plane of rotation.
Purpose of a transmission system
To transfer power from engine to the main rotors, tail rotor and other accessories
Purpose of mgb
Reduce the engines high RPM low torque to high torque low RPM for rotors
Components of a tail rotor drive system
MGB, drive shafts, tail rotor gearbox, and tail rotor
Main components of a transmission system (4)
MGB
TR Drive system
Clutch
Freewheel
4 forces acting on helicopter in hover
Directly upwards forces, thrust and lift, equal to the directly downward forces, drag and weight.
Forces in forward flight (2)
Total resultant thrust
Total resultant drag
Outline ground effect
When helicopter is hovering within 1 rotor diameter from the ground, it stops induced airflow through disc and the loft vector increases and less power is needed
Also reduces blade tip vortices
Define recirculation
When the same air passes through the disc, which is more turbulent and reduces production of lift.
Outline gyroscope precession
An input on a rotating mass, will have an output manifest 90 degrees in the direction of rotation. “Lag effect”
Define disymmetry of lift
Advancing blade travels faster in relation to the realitive air flow. And the retreating blade travels slower. Blades will flap to equality to reduce this.
How is retreating blade stall perceived when evident
Roll
Pitch up
Vibrations
Outline coriolis effect
Acceleration and deceleration as the rotor blades flap. When the centre of mass of a rotor blade moves towards the centre of rotation the blade will speed up.
Purpose of tail rotor [2]
Counter main rotor torque
Alter fuselage heading
Define translating tendency
When helicopter drifts from the thrust cuased by tail rotor to counter the rotors toqure.
To stop this. Manufacturers mount mast at a tilt
Translational lift
When helicopter moves forward at about 16 to 24knts it will move out of its downward and into clean air. This gives a boost in lift
4 defects of rotor blades
Delamination
Cracking
Erosion
Impact damage
