Propellers Theroy

Question 1

How is an airplanes thrust produced

Answer 1

By accelerating a mass of air

Question 2

What are the two two types of propeller theory’s

Answer 2

Momentum theory
Blade element theory

Question 3

What is momentum theroy

Answer 3

A pressure difference between the face and back of the blade

Question 4

What is the blade element theory

Answer 4

Each blade is made up of an infinite number or sections with a distance from the axis of the prop

Question 5

What are the sections of the blade

Answer 5

Blade face
Blade back
Plane of rotation which is a line running horizontally through the middle
Chord line that runs the length of the blade
Leading edge
Trailing edge
Axis of rotation
Blade angle

Question 6

What is propeller pitch

Answer 6

The angle between the chord line and the plane of rotation

Question 7

What are the three types of pitches

Answer 7

Geometric
Effective
Slip

Question 8

What is geometric pitch

Answer 8

Theoretically if a prop turned on revolution through a solid that is the distance

Question 9

What is effective pitch

Answer 9

Actual distance a propeller advances. Through the air in one revolution

Question 10

What’s the difference between the geometric and effective pitch

Answer 10

Slick

Question 11

What is the angle of attack

Answer 11

The acute angle between the chord line and the relative wind

Question 12

What is centrifugal force

Answer 12

Puts the greatest stress on a prop tries to pull the blades out of the hub

Question 13

What is thrust bending force

Answer 13

This force tries to bend the blades forward and is greatest near the tip of the blade

Question 14

What is torque bending force

Answer 14

Tries to bend the prop blade in its plane of rotation opposite of the direction of rotation

Question 15

What is aerodynamic twisting force

Answer 15

The force that tries to increase blade angle

Question 16

What is centrifugal twisting force

Answer 16

Force acting on the longitudinal axis of a prop tries to rotate the prop to a low pitch position

Question 17

What is asymmetrical loading

Answer 17

The loading in which a prop disk produces thrust more on one side of the blade

Question 18

The asymmetrical loading has a what

Answer 18

Critical engine

Question 19

What are the different types of props

Answer 19

Fixed pitch
Ground adjustible
Controllable pitch

Question 20

How does fixed pitch aircraft operate

Answer 20

They have different blades with diff ent blade angles that allow them for cruise and take off

Question 21

How do ground adjustible props work

Answer 21

By setting the blade angle with a universal prop protractor and rotating till the right angle the tightening the blade clamps

Question 22

What are the types of controllable pitch props

Answer 22

Two position propellers

Question 23

What are the two types of constant speed propellers

Answer 23

Counterweight
Non counterweight

Question 24

How do counterweighted props work

Answer 24

By pushing oil on a piston to move the blades into low pitch position
And the centrifugal force moves the blades back into the high pitch position

Question 25

How do no counter weight props work

Answer 25

It uses a spring and centrifugal twist to move it into the decreased pitch position and it uses oil pressure to move it into the increased pitch potion

Question 26

What are the major components of the propeller governor

Answer 26

The speeder spring that supplies the pressure for the flyweight assembly The spur gear type govenor oil pump that increases the pressure to the prop The pilot valve that controls where the oil flows

Question 27

What component can be adjusted to set the blade angle pitch

Answer 27

High RPM adjustment stop screw

Question 28

What are the three conditions of a propeller governor

Answer 28

Over speed On speed Under speed

Question 29

Where does oil flow when the counterweighted prop is at an overrated condition

Answer 29

Flows back into the oil pan

Question 30

Where does oil flow when an counterweighted prop is at an under speed condition

Answer 30

Into the propeller

Question 31

Where does oil flow on an non counterweighted prop in an over speed condition

Answer 31

Into the propeller

Question 32

Where does oil flow in an non counterweighted prop in an under speed condition

Answer 32

Into the oil sump

Question 33

What is the basic principle behind feathering constant speed props

Answer 33

Pressing an feathering button which will rotate the blades from low pitch to high pitch to extreme high pitch

Question 34

What are the different types of feathering constant speed props

Answer 34

Hamilton standard hydrostatic

Question 35

How does a Hamilton standard hydro magic control an under speed condition

Answer 35

Engine oil pressure overcomes governor oil pressure and is helped by centrifugal twisting moment so the blades move into a low pitch position so the engine can speed up

Question 36

How does a hdh control an over speed condition

Answer 36

High pressure from the governor pump is pushing the piston outward to move the blade into a high pitch position to slow the blade down

Question 37

What is already on the oil container to prevent engine oil draining out and not being able to feather the prop

Answer 37

The standpipe at the bottom of the oil container

Question 38

How does a hartzell steel hub operate

Answer 38

Same basic principles as the non feathering counterweight prop it uses oil pressure and and a govenor

Question 39

How does the hartzell steel hub feather the prop

Answer 39

By moving the governor control into the full aft position. This drains the oil out of the prop and the counterweights use centrifugal force to move them into the feather position

Question 40

How do you un feather a hartzell prop

Answer 40

Moving the governor control into its normal range and the oil pump with turn the prop into low pitch position once it rotates

Question 41

How does some hartzell feather their prop

Answer 41

By the use of an accumulator and it stores oil under pressure to allow for a faster switch

Question 42

What is used in a hartzell system to prevent the prop from feathering each time there is an engine shut down

Answer 42

High pitch stop plate which prevents the prop from going full feathered unless it is spinning

Question 43

How do McCauley constant speed props work different from others

Answer 43

They use a counterweight and a spring to assist in feathering

Question 44

How does the McCauley feather the prop

Answer 44

By moving the governor control into the aft position which raises the piolet valve and allows oil back into the sump. Centrifugal force holds the high pitch and the spring rotate the prop into the feathered position

Question 45

How does a McCauley prop unfeather their props

Answer 45

By the use of an accumulator to move the blades into the unfeathered position. The prop lever has to be controlled back to its normal conditions to go into the normal position