PROPELLER Flashcards
1
Q
What type of propeller on the PA44?
A
- constant speed (can change its pitch to maintain a constant RPM)
- controllable pitch (select desired RPM)
- feathering (rotates its blade parallel to the airflow)
- two bladed
- hartzell propellers
2
Q
What is the prop mounted to?
A
- the propeller is mounted directly to the engine crankshafts
3
Q
High RPM & Unfeather position
A
- oil pressure
4
Q
What forces are acting on the prop when it’s Low RPM or in a feather position
A
- nitrogen pressure & large spring
- prevents propeller overspeed
5
Q
Feathering Lock
A
- operated my centrifugal force (a force acting outwards on a body moving around its center)
- prevents feathering during engine shutdown when speed falls below 950 RPM
- no oil pressure in engine & speed is above 950 RPM prop will feather
6
Q
Components of the Prop
A
- prop lever
- speeder spring
- fly weights
- pilot valve
- engine oil pressure
- fluid valve that leads to prop hub
- prop hub: pitch change rod, piston & spring
- gears of the system is connected to the engine
7
Q
TO/LDG
A
- Lever forward, turns the screw
- Increases speeder spring tension
- flyweights fall in, valve opens
- oil enters prop hub moving the piston
8
Q
Cruise
A
- lever releases tension on spring
- flyweights fall out & oil escapes hub
- flyweights find equilibrium as RPM decreases moving valve to the closed position
9
Q
Forces acting on the prop in a unfeather state
A
- oil pressure & aerodynamic twisting keep prop unfeathered
10
Q
More oil =
A
More RPM
11
Q
Less oil =
A
Less RPM
12
Q
What position does the propeller want to revert if a failure occurs?
A
- feather position
13
Q
Feathering lock
A
- operated by centrifugal force
- prevents feathering during shutdown
- if starting a feathered prop, less thrust & power is being created
14
Q
What if the unfeathering accumulator fails?
A
- use the starter
- the accumulator is used for safety & practice purposes
- it helps prevent wear & tear of the starter
15
Q
How do I get oil into the prop if accumulator and starter fail?
A
- use the fuel pumps
16
Q
Why is compressed nitrogen air favored over other types?
A
- it contains no moisture
17
Q
Prop governor
A
- supplies engine oil at various pressures through the prop shaft to maintain a constant RPM setting
- controls engine speed by varying pitch
18
Q
Unfeathering accumulator
A
- stores engine oil under pressure from the governors
- released back to governors for prop unfeathering
