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Coverts the movement of air over its surface into a force useful for lift
Force produced by airfoil, perpendicular to relative windand opposes graviety
force acting on a body and opposite to relative wind. resistenace of the atmosphere to the motion of the aircraft
Force developed by the rotor bllades, parallel to relative wind, opposes weight and drag
distance from leading edge to trailing edge
Distance from root of blade to tip
Define angle of attack
Angle of Chord relative to the relative wind
Define relative wind
opposes direction of airfoil movement
When the angle of attack is exceeded, to low of airspeed
Define Centre of Pressure
the point on the airfoil where lift is produced
Define Pitch angle
The angle the blade is making to a reference point
What causes Coning
Lift and centifugal force or weight
What controls Vertical movement
and how-collective, changes blade pitches equally
What provides directional control, how is this accomplished?
Cyclic, changes pitches of blades opposite to each other
What provides Yaw control, and hows is this done?
Tail rotor pedals, collectivly changes pitch on the tail rotor pedals
Define Translating tendency
when you add or reduce power, it wants to move the nose of the aircraft
how is the a/c designed to compensate for translating tendency
mast is tilted 2 deg
Which was does the main rotor head rotate on a European a/c
CW When viewed from above
How is pitch changed on a individual rotor blade, which axis?
the feathering axis
why are the blades washed out
to comp for the lift across the lenght of the blade
Define Dissymmertery of lift
difference between the amount of lift on the advancing and retreating blades of the rotor system due to airspeed
what is it called when the blades flap up and down
how do you comp for corrilious effect, (what is adjusted)
lead-lag hinge, allows the blade to move fore and aft
Name 3 types of rotor heads
what direction can blades move in a rigid rotor system
only movement is pitch, blades can flex
What design feature is incorperated into some semi rigid rotor systems
under sliging comp for corrilious effect
what direction can blades move in a FullyArticulated rotor system
feathers flaps lead-lags
explain the transfer of motion that the swashplate provides
transfers movement of cyclic and collective from stationary push pull movements to rotating push pull movements in the rotor system
What does charactistic of a spinning rotor does the swashplate comp for
Define Translational Lift
Increase in lift as the rotor enters horzional flighthigher airflow velocity supplies a greater mass of air per unit of time
"A condition of increased drag and loss of lift at the aft portion of the rotor disc" is defined by what term
- Transvers Flow-Caused by the air having a greater induced velocity and angle
- -More lift in the front than the back
Self excitied viberations occurs on the ground is defined by what term?
What rotor head system is most seceptiable to ground resonance?
Fully Ariticulated, if out of phase
If the skid gear catches on a root or freezes to the ground before you try to take off,what would this condition be defined as?
What are the two primary reasons for blade stall?
- Insufficient airspeed
- Too great angle of attack
What would be an indicator of a blade about to stall
viberation of the main rotor head
What must the pilot do if he/she sences retreating blade stall?
- Unload rotor system
- slow down
Name the 2 Viberations that occour to the main rotor head?
- Lateral-out of balance
- Vertical-out of track
Name 3 types of viberations found in a helicopter
When dynamically balancing the main rotor, which should be balanced first? Balance or track?
Track then balance
'Lifting rotors are driven by the action of the air moving through the blades as the a/c decends' What term is used to describe this?
Name two different types of Freewheel unit?
What two procedures would require adjusting the lenght of the pitch links ?
- for autorotation
- for out of track
Condition of powered flight where the helicopter settles into its own downwash, (settling with power) -What is the proper name for this definition?
Vortex ring state
Name some conditions that can result in the Loss of Tail Rotor Effectiveness (LTE)?
- requires high power
- low airspeeed
- unanticipated manuevers
- No translational lift in main rotor-robs power from tail rotor resulting in LTE
Name 3 different types of tail rotor designs?
- Traditional design of two or more blades
What hinge is incorperated into the design of the rotor system to counter the efferct of dissymmerty of lift?
in a Notar helicopter, a design feature incorperated into the tail boom takes advantage of what aerodynamic princpal?
What is one of the main purposes of strakes on the tail boom?
help counter main rotor torque
Define engine derating, and why is it done?
- de-rated by making 100% torque at less power than the engine can produce
- because the power output decreases at altitude
name two types of clutches?
- belt tightener
What type of helicopter needs clutches?
Recip or fixed shaft, free turbines don't need a clutch
With regaurds to a tail rotor drive shaft, what are the two most important design considerations?
- Shaft must be flexiable (torque from tail boom)
- Must be driven when a/c is in autoration
Why is the vertical fin offset?
offset to move the tail rotor sideways, takes over for tail rotor at airspeed
Why is the horizontial stabilizer an inverted airfoil?
Holds the nose up in forward flight to reduce drag
How is the direction changed in a tandem rotor helicopter?
by changing the direction of thrust from each rotor system
Why is a stabilizer bar used on some two bladed rotor systems?
to increase dynamic stabability
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