Handout

Question 1

What is the purpose of a propeller

Answer 1

Convert engine power to thrust

Question 2

How does a propeller produce thrust

Answer 2

Bernoullis principle (Blade aerofoil)

Newtons 3rd law (cold jet principle)

Question 3

What is thrust in the context of propellers

Answer 3

Acts along the longitudinal axis of the aircraft

Question 4

What is torque (propellers)

Answer 4

Acts at right angles to the propeller longitudinal axis

Question 5

What forces are acting on a blade

Answer 5

centrifugal force 
thrust bending force
torque bending force
aerodynamic twisting moment 
centrifugal twisting moment

Question 6

What is centrifugal force trying to do

Answer 6

Pull the blades out of the hub as it spins

Question 7

What is thrust bending force

Answer 7

Similar to helicopter coning angle

The tips of the blade bend forward in the direction of travel

Question 8

What is torque bending force

Answer 8

Similar to lead and lag (helicopter)

Resistance to the air bending the blade in the opposite direction of rotation

Question 9

What is aerodynamic twisting moment

Answer 9

The aerodynamic twisting moment tries to increase the blade angle

Question 10

What is centrifugal twisting moment

Answer 10

The centrifugal twisting moment tries to decrease the blade angle

Question 11

Where is blade back and face

Answer 11

Blade face scoops the air, blade back is the side facing away from the pilots

Question 12

How is a prop connected to the hub

Answer 12

The shoulders on blade shank connect to the blade hub grooves

Question 13

What are blade stations

Answer 13

Used to specify points along the blade from their centre of rotation (the hub)

Question 14

What is the difference between angle of attack and pitch or blade angle

Answer 14

AOA Is the angle between the aerofoils chord line and the relative airflow.

Question 15

Blades are twisted, why?

Answer 15

The outside of the blade travels faster than the inside, blades have a twist to keep generate equal thrust along the entirety of the blade

Question 16

What is geometric pitch

Answer 16

How far the aircraft should travel forward due to the thrust produced by one full rotation of the propeller in theory

Question 17

What is effective pitch

Answer 17

How far the aircraft actually travels forward due to the thrust produced by one full rotation of the propeller in reality

Question 18

What is slip

Answer 18

The difference between geometric and effective pitch

Question 19

What is torque reaction

Answer 19

A twisting force exerted on aircraft due to the torque generated by the propeller spinning cause the aircraft to slowly roll

Similar to the torque produces by the main rotors on a helicopter

Question 20

What is on speed

Answer 20

The most efficient desired rpm for the propellers

Question 21

What is windmilling

Answer 21

Spinning freely in the wind

Question 22

What is feathering

Answer 22

Making the blades straight on for the least air resistance

Question 23

What is reversing the blades

Answer 23

Reversing the pitch to slow the A/C

Question 24

What is a negative torque system

Answer 24

prevents the torque from turning the engine, used in descent

Question 25

What is a de coupling

Answer 25

Disconnects prop from engine | Similar to a free wheeling unit

Question 26

What is auto feathering

Answer 26

Auto feather the blade to take the load off the pilot during takeoff

Question 27

What is a pitch lock

Answer 27

Safety feature that lock the propeller to provide thrust

Question 28

What is a propeller brake

Answer 28

Similar to a rotor brake

Question 29

What is the front spinner

Answer 29

Aerodynamic fairing

Question 30

What are the 3 purposes of a barrel ASSY

Answer 30

Hold blades in place Secure prop to shaft Transfer torque from engine to thrust

Question 31

What is inside the dome ASSY

Answer 31

The mechanism for changing blade angles

Question 32

Describe the components in a propeller assy

Answer 32

Front spinner (fairing) Dome (Stationary and rotating cam, piston ASSY) Barrell ASSY (retaining nut, front + rear cone) Rear spinner Afterbody (upper and lower) Control ASSY (upper and lower) Upper is the brains (Valve housing) Lower is the muscle (pump housing)

Question 33

What components make up the barrel assy

Answer 33

Front and rear barrel halves Front and rear cones (Cones expand against shaft and hold everything in place) retention nut and snap ring

Question 34

What is the purpose of blade cuffs

Answer 34

Improve airflow around the blade shanks Increase the flow of cooling air to the engine nacelle

Question 35

What is a fixed pitch prop

Answer 35

Prop can't change

Question 36

What is variable pitch blade

Answer 36

The blades have adjustable pitch Achieve best performance by adjusting the blade angle Hubs have clamp rings or bolts

Question 37

What are the three types of fixed pitch propellers

Answer 37

Climb (Slow) Cruise (faster) Constant speed (works best at high speed)

Question 38

What is a governor

Answer 38

device which automatically adjusts the angle of the aircraft propeller blade as necessary to maintain a constant engine speed under varying flight conditions. (send fluid to the dome to move the pitch change mechanism)

Question 39

What are the three purposes of a governor

Answer 39

Boost pressure of engine oil Control amount of oil that flows to the propellor Senses rotational speed of the engine

Question 40

What are the three main components in a governor

Answer 40

Fly weights Pilot valve Pump

Question 41

What are the two types of anti/de ice on props

Answer 41

Fluid and electrical heating elements Anti is used on the low speed area and around the engine nacelle

Question 42

How are props balanced

Answer 42

Vertically or horizontally. If its vertically balanced it will remain vertical regardless of what blade is facing up weights are added to balance

Question 43

What are protractors used for

Answer 43

Used to measure blade angle Calibrated off dome then held against blade to check it

Question 44

What are 3 lethal warnings

Answer 44

Keep clear of the propeller arc when the GTC or APU is operating or when an external air starter is connected Remove power IAW the relevant MM Open (pull) circuit breakers IAW relevant MM

Question 45

What are 4 safety precautions

Answer 45

Never walk through a Propeller Arc Use warning signs in the cockpit Isolate engine starter system Isolate propeller feathering system