Propeller Flashcards
What does CSU mean?
Constant speed unit
How do the blades move to a coarser pitch?
Counterweight and spring
Do we have a CSU in the DA42NG
Not really. The DA42NG has an electric governor.
What is the max t/o rpm
2300 rpm
How long is this allowed
5 minutes per flight
What is the max continuous RPM
2100 rpm
Is any overspeed allowed
2500 rpm for up to 20 sec
What kind of governor is in the NG
Electric
What decides on the pitch
ECU
What changes the pitch blade angle
Gearbox oil
To increase the pitch, do you add or remove oil from hub?
You lower oil pressure
What happens to rpm
Decreases
If oil pressure increases in the hub, what happens to pitch
Pitch decreases
What happens to rpm
Rpm increases
What system allows unfeathering
The pressure accumulator
What’s the pressure in it
320 psi
When it activates, it moves the pitch into low or high pitch
Low
How does the feathering work
Electric governor valve opens. All oil from hub leaves.
Is feathering possible at all times
No, only above 1300 rpm
What is the prop made of
Wood + reinforced fiberglass plastic coating
Can we move the prop by hand
We should not
What happens if we do
Could damage the gearbox
If loss of oil pressure or engine failure, will the prop auto feather
No
What will happen
Prop moves to high pitch angle
How to feather then
The engine master must be off
When the prop is turning, what happens naturally to the blades
Move to lower pitch
What’s this called
Aerodynamic twisting
How to offset that
Counterweight + spring
The counterweights move the pitch into low or high pitch
High (coarser)
When the prop is rotating under 1300 rpm, what prevents the prop from feathering
Pitch stop locks
When you shut down the engine on the ground, does the prop feather
No
Why
Pitch stop lock
So how come you can feather in flight
Centrifugal latching mechanism disengage the pitch stop locks when > 1300 rpm
Recap: what conditions you need to feather the prop
2: Engine master off and rpm > 1300 rpm
What’s the prop pitch angle in the feather position
81 degrees
How does the prop unfeather
By using oil stored in the accumulator
What signals the accumulator to release oil to the hub
Engine master on
Can one use windmilling to restart the engine
No
What kind of CAS message could we get if we do
L/R ECU A/B FAILURE
What does CAS mean
Crew alerting message
