Rotary Flashcards
Types of helicopters
Single rotor
Tail rotor
Tandem
Coaxial
NOTAR
Torque reaction
A body is suspended above a mass is wanting to spin in the opposite way
Collective lever
Changes the pitch of the blades by the same amount at the same time
Cyclic controller
Varies the pitch of each blade not as a collective (cyclically)
Yaw pedals
Changed pitch of the tail rotor blade to oppose torque reaction
Throttle (5 types)
Manual/mechanical
Hydro mechanical
FCU
ECU
FADEC
Flapping to equality
Perpendicular movement to the rotor disc - aloud to happen due to flapping hinge
Advancing blade ascends AoA decreases less lift
Retreating rotor Descends increased AoA more lift
= due to this they go back to the original path (level)
Blade pitch
Angle between cord and plane rotation
RAF
Resultant of the induced airflow vector and the rotational airflow vector
Wash out
Decreases the pitch
Limiting factors of RRPM
over pitching
Transmition considerations
Compression limits
Coning angle
4 types of rotor heads
Teetering
Fully articulated
Semi rigid
Fully rigid
Delta three hinge
Allows the blades to change pitch as it flaps (tail rotor)
Teetering rotor head
One hinge
Feathering hinge
Fully articulated
Three hinges
Feathering
Flapping
Dragging
Semi rigid rotor head
One hinge
Feathering
Fully rigid rotor head
No hinges
Vertical climb
Pilot raise collective
Blade pitch increase
Rotor thrust increases
Lift
RRPM and torque reaction increases
Yaw input required
Induced airflow vector increased
AoA lowers to 4•
Steady rate of climb achieved
Pilot balances collective to enter hover
Ground effect
Helicopter is 50-100ft of the ground
Airflow through the discs meets the ground to form a divergent duct
This increases as there’s pressure below the discs which increases AoA and increases the total rotor thrust
Less power is needed to hover in this region
To land the pilot has to power through
Factors that affect ground effect
Height
Wind
Nature of the ground
Slope
Horizontal moment
(Two components)
Vertical component
Horizontal component
Push cyclic forward - changes pitch individually
Disc tilts
CoG moves forward nose drops
Aircraft loses altitude - pilot raises collective to maintain height
Aircraft gets faster - flap back occurs
Pilot overcomes flap back
Transition phase of flight (16-24knots)
Tail lowers and nose comes up
Translation phase starts
Aircraft continues to accelerate at 60 knots and collective is down = aircraft is in fully forward flight
Flap back
Disymetry of lift and flapping to equality happening longitudinally
Advancing blade experiences an increase in airflow velocity and AoA & will rise
Reverse happens to retreating blade and the disk will tilt up
Rotor disc
The circular area that a helicopters rotor blades sweep through during rotation
Coning angle
Angle measured between the length of the blade and the blades tip path plane
