15.16 Turboprop Engines Flashcards
What is a turboprop engine known as?
A gas generator/ producer engine.
How can a gas coupled/ free power turbine be identified?
There are no mechanical connections between the gas generator and the free power turbine.
What are the advantages of a gas couple/ free power turbine?
Vibration isn’t directly transmitted to the gas generator.
Engine is easier to start.
Propellor can be held at low rpm=low noise + blade erosion.
Propellor brake can be used during loading= engine can be used as an APU.
How does a gear/direct coupled turbine differ from a free power turbine?
It has extra turbine discs.
What does the gear/direct coupled turbine do?
Transmitter increased power forwards.
In a gear/ direct coupled turbine, because the propeller is driven by the engine what is necessary?
Complex integrated propeller control system.
How is constant speed achieved in a gear/ direct coupled turbine?
Propeller pitch and fuel flow are coordinated.
For small reductions, what gears are used?
Spur gears.
For larger high torque reductions, what gears are used?
Epicyclic gears.
How is oil viscosity different than a turbo jet engine?
It is higher, due to heavier loads been imposed on gears.
What are the 2 main types of reduction gears?
Parallel spur.
Epicyclical.
What are the advantage and disadvantage of straight cut parallel gears?
+ Lowest friction losses
- But noisy.
When may heavy duty bearings be required?
When torque changes create high loading on gear teeth.
What are the advantages of helical parallel gears?
Allow gradual onset of torque changes,
Quieter
What is the disadvantage of helical parallel gear?
Less efficient power transmission.
What is an annulus also known as?
Ring gear.
In a fixed annulus system, which way does the propeller spin?
Same direction as power turbine shaft.
In a rotating annulus system, which way does the propeller spin?
Oppositely to the power turbine shaft.
What is flight range known as?
Alpha range.
What is ground handling range known as?
Beta range.
When is the feathering system used?
When an engine shut downs in flight.
Can propellers be unfeathered in flight?
Yes, to restart the engine.
Where is single lever control used ?
On gear coupled engines.
What makes up a single lever control?
An integrated fuel and propeller control unit.
And a PCU.
Where is Dual lever control used?
With free power turbines.
What is the purpose of the thrust lever?
Schedules fuel flow.
What is the BETA/ ground operating propeller angle range?
+20 to -20 degrees.
Where is the propeller lever operated?
In flight.
What is the purpose of control locks?
Ensure control surfaces don’t flutter on ground with engines running.
What system prevents propeller windmilling?
Automatic Drag Limiting System (ADLS)
What is the feathering angle of ADLS?
90
What is the purpose of ADLS?
Prevents propeller from driving engine in case of oil supply failure.
What powers ADLS?
Feathering pump
Where does the feathering pump get its oil supply from?
Draws oil from engine tank
What are the 3 over speed safety devices?
Pitch locking.
Propeller over speed govenor.
Turbine shaft failure.
What is the purpose of pitch locking?
Prevents propeller moving to a fine pitch angle.
How does pitch locking work?
It moves under spring force when oil supply fails.
What does the propeller over speed govenor do?
Dumps oil pressure to return if propeller speed exceeds 105%
What happens in the event of turbine shaft failure?
Engine fuel supply is immediately shut down.
