What is a turboshaft engine optimised to produce?
Shaft power rather than thrust.
How is the output of a turboshaft engine measured?
In shaft horsepower (SHP).
Why are turboshaft engines widely used in helicopters?
They have a high power-to-weight ratio, compact size, and high reliability.
Name the two main sections of a turboshaft engine.
The gas generator section and the power section.
What components make up the gas generator section?
Compressor, combustion chamber, fuel nozzles, igniters, and turbine stages.
What components make up the power section of a turboshaft engine?
Additional turbine stages, reduction gearbox, and output shaft.
What is a free power turbine?
A turbine not mechanically connected to the gas generator, driven only by exhaust gases.
What are the advantages of using a free power turbine?
Improved starting, flexibility, and load response.
What are the main applications of turboshaft engines?
Helicopters and auxiliary power units (APUs).
What does a turboshaft engine drive in a helicopter?
The main rotor gearbox.
Why is a reduction gearbox required in turboshaft engines?
To reduce high turbine RPM to usable output speeds.
What is the function of the output shaft?
To transmit power to the main gearbox or driven equipment.
What is the purpose of a freewheel or sprag clutch in multi-engine installations?
To prevent one engine from driving another.
Where does additional speed reduction often occur in helicopters?
In the main rotor gearbox.
Why are flexible couplings and universal joints used in drive systems?
To accommodate misalignment, vibration, and transmission movement.
How are flexible couplings designed to fail?
Gradually and visibly to allow detection during inspection.
What is the purpose of the turboshaft fuel control system?
To regulate fuel flow and protect engine limits such as RPM and temperature.
What control systems are used on modern turboshaft engines?
Electronic Engine Control (EEC) or FADEC.
What does OFF mode select in helicopter engine control?
Engine shutdown or abort start.
What does FLIGHT mode select in helicopter engine control?
Full engine speed with FADEC adjusting fuel flow to meet power demands.
