Propeller Pitch Control Flashcards
What is disc braking?
Propeller blades moved to fine pitch on landing causing negative angle of attack therefore braking force.
What is power ON braking?
Propeller blade moved to negative blade angle to resist rotation so power can be applied proportional to braking force
What is feathering?
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.
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?
Under-speed condition. Forward. Increased. Down
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?
Over-speed condition. Backwards. Decreased. Up
How does a counterweight type propeller work? What does oil pressure do?
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
How is electrical power supplied in an electrical operated pitch change mechanism?
Through a slip ring and bush assembly
What is the difference between electronic and electric operated pitch change mechanisms?
Electronic has a 2-stage servo valve instead of a governor unit
What is the accuracy of an electronic operated pitch change mechanism?
Accurate to within 2 propeller revolutions per minute of the demanded value
What is the function of the torque motor in an electronic operated pitch change mechanism?
Produces correct metered oil supply to the pitch change mechanism
How is oil pressure used in a single acting propeller?
Oil pressure changes the pitch in 1 direction only.
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?
Oil pressure moves blades to course pitch, spring moves blades to fine pitch. Fine pitch as favourable for windmilling and engine restarts
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?
Oil pressure moves blades to fine pitch, springs and torsional moments move blades to coarse pitch. Coarse pitch
What pitch changing moment does the centrifugal force of the propeller blade mass produce? What is used to counteract this?
Blade turns in direction of fine pitch. Counterweights at blade root
What pitch changing moment does the centrifugal force of the propeller blade mass produce? What is used to counteract this?
Blade turns in direction of fine pitch. Counterweights at blade root
How is oil pressure used in a double acting propeller?
Oil pressure moves in both directions
What phases of flight is auto feathering used?
Take off and cruise
What prop speed does the primary governor work till?
102 to 103%
What prop speed does the overspeed governer work over?
104 to 106% Np
What prop speed does the Py pressure from the FCU in the primary governer work over?
106 to 107% Np
What 4 conditions is Up trim triggered regardless of Auto feather selection?
- Torque of engine falls below 25%
- NP falls below 80%
- PLA is in the rating detent
- MTOP not set
When will the ARM light turn on after you’ve selected auto feather ON?
Engine torque exceeds 50% and power levers advanced past 60 degrees
What do dual trim signals do? Where are they sent? What do they replace?
Increase only engine by 10%. FADEC. Replace Normal Take Off Power and Max Take Off Power
What does an unfeathering accumulator do?
Provides a reserve of pressure to move blade to low pitch for engine restarting
What do centrifugal latches do? How are the latches engaged? How are latches disengaged?
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
When is max fine pitch used? Why?
Rapid acceleration during take off. Allows shorter take off run
When is coarse (high) pitch used?
High forward speed
When is ground fine pitch used?
Engine starting and disc braking
When is negative (reverse) pitch used?
Power-on-braking and manoeuvring
What is the BETA range controlled by?
Pilot
What is the ALPHA range controlled by?
Propeller governer
