Heli Final Flashcards by Euan Mark

what are the four blade movements

feathering
teetering
flapping
lead/lag

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what are the three basic types of rotor heads

rigid
semi-rigid
fully articulated

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what is the main rotor strap? what purpose does it serve

they are wraps fine steel wire between two bearings.

they are designed to retain the rotor blades while still allowing for movement of the blade

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what is a droop stop? what type of rotor heads will they be found on

droop stops limit how far down a blade will settle, eliminating any damage to the airframe.

will be found on rotor heads that flap

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what are teeter stops? what are the two types

stops that limit the downward travel of semi rigid rotor heads

static and dynamic stops

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what are the different ways a main rotor head can be lubricated

oil or grease

self lubricated components

life lubricated components

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what is an example of a self lubricated component

Teflon Bearing

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what does the term life lubricated mean

the component is lubricated by the manufacturer and will not be re-lubricated for the usable life of the component

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what is a rotor disc

the total surface area occupied by the main rotor assembly while in motion

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what is coning

the upwards angle of the rotor blades while in flight. resultant of the creation of lift

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what is an autogyro? how does it differ from a helicopter

an autogyro uses an un controlled / unpowered rotor system to produce lift. can only produce lift during forward flight

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what effect does centrifugal force have on rotor blades in motion

it will cause the rotor blades to stay flat until lift is increased

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what is Nr

rotor RPM

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when lift is increased, what happens to the rpm of the main rotor

the RPM always stays constant at 100%. all flight inputs are done by changing blade pitch, not blade speed

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what defines a hover

all forces are equal

zero movement relative to wind speed

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what is gyroscopic precession

any blade pitch adjustment made during directional flight must occur 90 degrees early

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how will the airframe react to the torque forces of the main rtor

the airframe will always react in the opposite direction of the main rotor

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what is induced flow

the direction of airflow through the rotor blades during directional travel

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what is translational lift

the transition from hover to directional flight. reduces the induced flow angle and causes light airframe buffeting

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why is there no ground effect when flying frward at low altitude

the rotor downwash is propelled to the rear of the aircraft and does not create an air cushion for the aircraft to rest on

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what is dissymmetry of lift

difference in blade speeds while in directional flight

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what are the solutions for dissymmetry of lift

flapping hinge

differential cyclic

what is differential cyclic

a difference in blade pitch dependent of position

what is the law of conservation of angular momentum

when the centre of mass of a rotating object moves towards the centre of rotation, the object will accelerate

what are the solutions for the law of conservation of angular momentum problem

lead lag hinge | underslung mounting

what is mast bumping

the rotor head striking the mast. only occurs in underslung rotor heads

what pilot input controls yaw? how is yaw controlled

anti torque pedals at the pilots feet controlled by changing the pitch angle of the tail rotor blades

what control devices are incorporated into the tail rotor system

push pull tubes or teleflex cables connected to bell cranks which move walking beams to change pitch

what are some examples of additional controls located on the collective

``` landing lights start switch governor controls idle release throttle twist grip pop out float trigger ```

what are some additional controls that are located on the cyclic

push to talk radio cargo hook release trim

what is the purpose of the mixing unit

converts individual cyclic and collective input into a common set of outputs prevents collective inputs from altering cyclic position

what is centrifugal twisting force? what is used to combat it

a force acting on a rotor blade attempting to return it to a low pitch angle counterweights and collective spring

what is aerodynamic twisting force

forces acting on rotor blades to return them to a higher pitch

what are hydraulic servos used for

provides flight control boost and eliminates rotor system feedback

what are the different types of gearboxes

main rotor tail rotor intermediate combining

how is the main rotor gearbox mounted on a bell 206

using 2 a-frame support links to hold the gearbox and still allow movement

when is a clutch required on a helicopter

for all piston engine aircrafts and all direct drive turbine engine aircrafts

what are the two types of turbine engine

free turbine and direct drive turbine

what type of helicopters have freewheeling untis? are any of them manual

all helicopters have freewheel units and they are all automatic

what two measurements are displayed on a dual tach

engine RPM and rotor RPM measured in percent

what are drive shaft couplings

they are flexible metal plates or greased bearings that allow the drivetrain to move with the airframe without being damaged

what is a side effect of tail rotor anti-torque forces

translating tendency (lateral drift)

how do you counteract translating tendency

Pilot mixing unit which applies slight lateral cyclic when collective is moved

why mount the tail rotor higher on the vertical stab

more ground clearance brings the tail rotor in line with CofG

what is a delta hinge

the teeter hinge on a tail rotor that is not at a right angle with the blades. causes blades angle of attack to lower when flapping up

what do strakes do

the eliminate the ow pressure zone on one side of the tailboom which increases tail rotor efficiency

what is autorotation

the state of flight where the main rotor system is being turned by the action of relative wind instead of engine power

what are the different regions of the rotor disc duriong autorotation

stall region from centre to 25% of the blade autorotation region 25 - 75% of blade driven region 75% - blade tip

what are the different multi rotor configurations

co-axial (stacked) Tandem (one in front of the other) Synchrocopter (intermeshing)

what is a design feature that helps to overcome nose down tendency

forward tilt of mast or horizontal stabilizers

what is the purpose of a synchronized elevator

changes the CofG

during start up, fully articulated rotor blades will have a tendency to what?

lag

how are coning stresses reduced in rotor blades

pre coning angles

what must be recorded during autorotational rigging

a/c weight pressure altitude temperature rotor rpm