Propellers

Question 1

Why do some aircraft engines have a critical range of operation?

Answer 1

The engine and propeller combination have a resonant frequency problem in which excessive vibration can occur at certain ranges of RPM. The tachometer for an aircraft with this limitation is marked with a red arc. When it is necessary to pass through this range, it must be done as quickly as practical

Question 2

Does centrifugal twisting moment on a propeller blade tend to move the blades toward a high pitch or low pitch?

Answer 2

Low pitch

Question 3

Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch?

Answer 3

High pitch

Question 4

What is the function of the accumulator used with some McCauley feathering propellers?

Answer 4

The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help the propeller blades move toward low pitch when the propeller is being unfeathered

Question 5

What is meant by the alpha range of operation of a turboprop propeller?

Answer 5

This is the in-flight mode of operation from takeoff to landing

Question 6

Should an adjustable-pitch propeller be in high pitch or low pitch for takeoff?

Answer 6

Low pitch

Question 7

What can be done to prevent the front cone from bottoming when installing a propeller on a splined shaft?

Answer 7

Install a spacer behind the rear cone to move the propeller forward on the shaft

Question 8

Why is a propeller indexed to the engine crankshaft?

Answer 8

The relationship between the propeller and the engine crankshaft is chosen to produce the minimum vibration

Question 9

What does the pilot do to change the RPM of an engine equipped with a constant-speed propeller when it is operating within the constant-speed range?

Answer 9

The pilot moves the propeller pitch control. This changes the compression on the speeder spring inside the governor which moves the pilot valve. The pilot valve directs oil into or out of the propeller to change the pitch of the blades. The change in pitch changes the air load on the propeller which changes the RPM

Question 10

What is the difference between a controllable propeller and a constant-speed propeller

Answer 10

Basically, it is the control system. A controllable-pitch propeller uses a manually operated oil valve to control the pitch, and a constant-speed propeller uses a governor to control the valve

Question 11

When making a magneto check on an engine equipped with a constant-speed propeller, should the propeller control be in the low-pitch or the high-pitch position?

Answer 11

Low-pitch, high RPM

Question 12

What is the function of a propeller?

Answer 12

The propeller blades create thrust to pull or push an airplane through the air.

Question 13

What is the difference between a fixed pitch propeller and a controllable pitch propeller?

Answer 13

A fixed pitch propeller is one that has a built-in blade angle that cannot be changed by the pilot. A controllable pitch propeller is one that can be changed by the pilot and is usually controlled by a governor that maintains a constant speed.

A fixed pitch propeller is one that has a built-in blade angle that cannot be changed by the pilot.These propellers can have the blade angle changed by the manufacturer or an approved repair station to optimize performance. A controllable pitch propeller is one that can be changed by the pilot and is usually controlled by a governor that maintains a constant speed. Some controllable propellers also provide reverse pitch and feathering.

Question 14

How are some wooden propeller blades protected from wear and damage?

Answer 14

By metal tipping fastened to the leading edge and tip

Question 15

What happens to the blade angle of a constant speed propeller during a constant power drive?

Answer 15

The blade angle increases to prevent an overspeed.

Question 16

What are the functions of a constant speed propeller governor?

Answer 16

1. Boosts engine oil pressure before it enters the propeller hub
2. Senses rotational speed of the propeller
3. adjusts oil flow to the propeller hub to change the pitch and speed of the propeller

It boosts engine oil pressure before it enters the propeller hub, it senses rotational speed of the propeller, and then adjusts the oil flow to the propeller hub to change pitch and, therefore, speed of the propeller.

Question 17

What is the purpose of the propeller counterweights?

Answer 17

Centrifugal force acting on the counterweights causes the blade angle to increase.

Question 18

What is meant when a propeller governor is in an “on-speed” condition?

Answer 18

The governor is not accelerating or decelerating and the speeder spring and flyweight forces are in balance.

Question 19

How is a constant speed feathering propeller feathered?

Answer 19

Controlled by the governor or manually by the pilot by moving the propeller control into the feathering detent

By releasing oil pressure in the governor, the counterweights and feathering spring move the propeller into feather. This happens automatically if the governor oil pressure drops to zero (following an engine failure in most turboprops), or can be manually controlled by the pilot by moving the propeller control into the feathering detent.

Question 20

What is an unfeathering accumulator?

Answer 20

It is an oil accumulator used to provide oil pressure to unfeather a propeller.

Question 21

What is “alpha range” and “beta range” and where are they found?

Answer 21

Alpha: Constant speed mode in flight
Beta: Zero or minimum thrust range and reverse thrust mode on the ground

What is the alpha and beta ranges pertain to the operating modes of turboprops reversible-pitch propellers. In the alpha range, the propeller is operating in the standard, constant speed mode, which is usually in flight. In the beta range, the propeller is operating in the zero or minimum thrust range and negative thrust or reverse thrust mode, which is usually on the ground.

Question 22

What systems are commonly used for propeller ice control?

Answer 22

Fluid (alcohol) and electrical heat applied to the propeller blade root.

Question 23

What propeller repairs can be performed by a certified mechanic with a powerplant rating?

Answer 23

Only minor repairs and alterations can be performed by a certified mechanic with a powerplant rating. Major repairs must be performed by the manufacturer or a certified repair station. The propeller manufacturer’s maintenance manual outlines the scope of repairs.

Question 24

How are wooden propellers generally cleaned?

Answer 24

With a brush or cloth and warm water with mild soap.

Question 25

Where would you find the correct method and technique for cleaning an aluminum propeller and hub?

Answer 25

The propeller manufacturer’s maintenance instructions.

Question 26

What type of nondestructive testing should be accomplished to a propeller after blending?

Answer 26

The procedures recommended by the manufacturer.

Question 27

What are the two criteria used by many manufacturers to determine the amount of bend damage that can be repaired by cold bending of aluminum propellers?

Answer 27

The extent of the bend and its blade station location.

Question 28

How can repair file marks be removed from an aluminum propellers?

Answer 28

With very fine sandpaper.

Question 29

When performing a static balance on a two bladed propeller, what positions must the propeller be placed in when measurements are taken?

Answer 29

Vertical and horizontal positions.

Question 30

What is a propeller protractor used for?

Answer 30

It is used to measure propeller blade angle.

Question 31

What blade conditions can cause engine vibration?

Answer 31

The propeller being out of balance or an incorrect blade angle setting

Vibration can be caused by a propeller being out of track and/or balance, as well as incorrect blade angle setting.

Question 32

What is blade tracking?

Answer 32

Blade tracking is a procedure that compares the position of the propeller blade tips relative to each other.

Question 33

What controls both manifold pressure and rpm on an engine equipped with a fixed pitch propeller?

Answer 33

The throttle.