Propeller Pitch Control

Question 1

What is disc braking?

Answer 1

Propeller blades moved to fine pitch on landing causing negative angle of attack therefore braking force.

Question 2

What is power ON braking?

Answer 2

Propeller blade moved to negative blade angle to resist rotation so power can be applied proportional to braking force

Question 3

What is feathering?

Answer 3

If an engine fails then disc braking occurs which is bad so blades moved too max coarse pitch until chord line is 90 degrees to plane of rotation.

Question 4

If a pilot requires a higher propeller RPM what condition occurs in the propeller governor? Is the control lever moved forwards or backwards? Is tension on the seed spring increased or decreased? Does the pilot valve move up or down?

Answer 4

Under-speed condition. Forward. Increased. Down

Question 5

If a pilot requires a lower propeller RPM what condition occurs in the propeller governor? Is the control lever moved forwards or backwards? Is tension on the seed spring increased or decreased? Does the pilot valve move up or down?

Answer 5

Over-speed condition. Backwards. Decreased. Up

Question 6

How does a counterweight type propeller work? What does oil pressure do?

Answer 6

Counterweight attached at each root of the blade that overcomes CTM and exerts a force that turns the blade to a coarser blade angle. Oil pressure counteracts this and moves to a finer blade angle

Question 7

How is electrical power supplied in an electrical operated pitch change mechanism?

Answer 7

Through a slip ring and bush assembly

Question 8

What is the difference between electronic and electric operated pitch change mechanisms?

Answer 8

Electronic has a 2-stage servo valve instead of a governor unit

Question 9

What is the accuracy of an electronic operated pitch change mechanism?

Answer 9

Accurate to within 2 propeller revolutions per minute of the demanded value

Question 10

What is the function of the torque motor in an electronic operated pitch change mechanism?

Answer 10

Produces correct metered oil supply to the pitch change mechanism

Question 11

How is oil pressure used in a single acting propeller?

Answer 11

Oil pressure changes the pitch in 1 direction only.

Question 12

What moves the blades in the direction of coarse pitch and low pitch in a single acting propeller for single engine a/c? What position are the blades in after engine shutdown and why?

Answer 12

Oil pressure moves blades to course pitch, spring moves blades to fine pitch. Fine pitch as favourable for windmilling and engine restarts

Question 13

What moves the blades in the direction of coarse pitch and low pitch in a single acting propeller for multi engine a/c? What position are the blades during engine failure?

Answer 13

Oil pressure moves blades to fine pitch, springs and torsional moments move blades to coarse pitch. Coarse pitch

Question 14

What pitch changing moment does the centrifugal force of the propeller blade mass produce? What is used to counteract this?

Answer 14

Blade turns in direction of fine pitch. Counterweights at blade root

Question 15

What pitch changing moment does the centrifugal force of the propeller blade mass produce? What is used to counteract this?

Answer 15

Blade turns in direction of fine pitch. Counterweights at blade root

Question 16

How is oil pressure used in a double acting propeller?

Answer 16

Oil pressure moves in both directions

Question 17

What phases of flight is auto feathering used?

Answer 17

Take off and cruise

Question 18

What prop speed does the primary governor work till?

Answer 18

102 to 103%

Question 19

What prop speed does the overspeed governer work over?

Answer 19

104 to 106% Np

Question 20

What prop speed does the Py pressure from the FCU in the primary governer work over?

Answer 20

106 to 107% Np

Question 21

What 4 conditions is Up trim triggered regardless of Auto feather selection?

Answer 21

• Torque of engine falls below 25%
• NP falls below 80%
• PLA is in the rating detent
• MTOP not set

Question 22

When will the ARM light turn on after you’ve selected auto feather ON?

Answer 22

Engine torque exceeds 50% and power levers advanced past 60 degrees

Question 23

What do dual trim signals do? Where are they sent? What do they replace?

Answer 23

Increase only engine by 10%. FADEC. Replace Normal Take Off Power and Max Take Off Power

Question 24

What does an unfeathering accumulator do?

Answer 24

Provides a reserve of pressure to move blade to low pitch for engine restarting

Question 25

What do centrifugal latches do? How are the latches engaged? How are latches disengaged?

Answer 25

Prevent oil getting trapped in cylinder leading to bladder moving to coarse pitch by mechanically locking piston in fine pitch position. Spring pressure. Centrifugal force

Question 26

When is max fine pitch used? Why?

Answer 26

Rapid acceleration during take off. Allows shorter take off run

Question 27

When is coarse (high) pitch used?

Answer 27

High forward speed

Question 28

When is ground fine pitch used?

Answer 28

Engine starting and disc braking

Question 29

When is negative (reverse) pitch used?

Answer 29

Power-on-braking and manoeuvring

Question 30

What is the BETA range controlled by?

Answer 30

Pilot

Question 31

What is the ALPHA range controlled by?

Answer 31

Propeller governer