Module 15.17 Turboshaft Engines Flashcards
What is a turboshaft engine optimised to produce?
Shaft power (torque).
What two ways can the output shaft be connected?
Directly to the engine turbine or driven be it’s own turbine (free-turbine).
What is the turboshafts’s output measured in?
Shaft Horsepower (SHP).
Name the two parts of the engine?
Gas Generator
Power section
What does the power section consist of?
Stages of turbines, a gear reduction system, and the shaft output.
What are turboshaft engines used for?
Helicopters and Auxiliary Power Units (APUs)
Why are drive systems fitted to turboshaft engines?
To transfer the power produced to the components it must drive.
What is used to reduce the output RPM?
A reduction gearbox.
Where does the power go after the reduction gearbox?
It’s transmitted by a coupling shaft into the main rotor gearbox for further reduction.
What are both engines connected to?
Common gearbox
How is one engine prevented from driving the other?
A freewheel unit
What does a freewheel unit do?
Automatically disconnects the slower engine, usually in the form of a sprag clutch.
What allows the engine to drive the main rotor gearbox?
An output shaft from the engine gearbox
What is normally fitted in the output shaft?
Universal joint
What does the universal joint in the output shaft do?
Ensures the drive shaft alignment between the engine and the main rotor gearbox.
Also absorbs the low amplitude oscillations.
What ensures enough movement of the transmission can take place?
A universal joint connection at the transmission on the housing
What is inside the transmission housing?
The drive shaft.
What must the drive shaft not carry?
Tension or compression loads.
Why must the drive shaft inside the transmission be flexible?
Deflections caused by the transmission’s movements.
What allows the drive shaft inside the transmission to be flexible?
A coupling made up of stainless-steel discs bolted to the shaft (thomas coupling) to provide a flexible joint.
What are the accessories in a turboshaft engine driven by?
The gas generator or power section.
What is the freewheel unit usually in the form of?
A sprag clutch
What happens when the engine mode is set to “flight”?
The engine runs at full speed.
