Propellers Flashcards
How are the props driven
Via a reduction gearbox
Type of propeller
3 blade, constant speed, feathering
Direction of rotation as seen from the cockpit
Left prop
And right prop
Both clockwise
Which is the critical engine
Left
Blade construction
Wood composite with steel leading edge
What 3 things control pitch angle
FADEC>CSU>PCU
Full Authority Digital Engine Control controls Constant Speed Unit, which controls Pitch Control Unit
What things cause the props to fine
Oil pressure from the CSU
Centrifugal twisting moments of the blades
What things cause the props to coarsen
A spring in the propeller hub
Centrifugal twisting moments of the counterweights
What oil does the CSU use to control blade pitch
High pressure oil from the gearbox pump
How does the CSU control the amount of oil going to the PCU
An electrically operated governor valve in the CSU
How is oil pressure to the CSU maintained in negative g
A capillary tube
What is the oil in the accumulator charged with
Nitrogen gas
How is the accumulator shutoff valve closed
When ENG MAST is switched off
How is the prop feathered in flight
ENG MAST OFF stops flow of oil to the CSU, allowing springs and counterweights to coarsen the blades
How is the prop unfeathered in flight
ENG MAST ON opens accumulator shutoff valve, allowing pressurised oil to reach the CSU for it to fine the blades
What is the function of the accumulator
Ensure there is enough high pressure oil available to unfeather the blades, even if the engine isn’t running, and that a constant uninterrupted flow is provided to the CSU, even if gearbox pump flow reduces momentarily
Below what RPM will the prop blades not feather
1300 rpm
What stops the blades feathering below a certain RPM
A centrifugal latch holds them at the start lock position
What angle are the blades at the feathered and stop lock positions
Approx 81 deg
Approx 15 deg
