15.17 Turboshaft Engines Flashcards
What is a turboshaft engine optimized for?
Producing shaft power to drive machinery instead of producing thrust.
What are the two major parts assemblies of a turboshaft engine?
- Gas generator
- Power section
What does the gas generator of a turboshaft engine consist of?
- Compressor
- Combustion chambers with ignitors and fuel nozzles
- One or more stages of the turbine
What is the output of a turboshaft engine measured in?
Shaft Horsepower (SHP) instead of thrust.
Where is the reduction of engine RPM typically done in a turboshaft engine?
At the rear of the engine where the power turbine drives the reduction gearbox.
What is the function of the drive systems in turboshaft engines?
To transfer the power produced within the engine to the components it must drive.
What is the purpose of a freewheel unit in a dual-engine turboshaft setup?
To prevent one engine from driving the other.
What does a universal joint do in a turboshaft engine’s output shaft?
Ensures drive shaft alignment, absorbs low amplitude oscillations, and opposes the engine’s torque reaction.
What does reduction gearing do in a turboshaft engine?
Reduces the extremely high speeds of gas turbine engine output to usable levels.
What is the construction of the coupling in a turboshaft engine?
Made up of stainless-steel discs bolted to the shafts to provide a flexible joint.
What does FADEC stand for?
Full Authority Digital Engine Control.
What is the role of Electronic Engine Controls (EEC) in turboshaft engines?
To adjust engine fuel flow to provide desired power without exceeding RPM and turbine inlet temperature limitations.
Fill in the blank: The control system of a turboshaft engine receives a signal from the flight crew for a given level of _______.
power
True or False: Turboshaft engines are commonly used in applications that require high power output and reliability.
True
What are the typical operating modes for FADEC-controlled engines in medium to large helicopters?
- Off
- Idle
- Flight
What happens to the freewheel unit during an autorotation?
Both units become disengaged, preventing the main rotor from driving the engines.
What is the main difference between turboshaft engines and turboprops?
Turboshaft engines are optimized for shaft power, while turboprops are optimized for thrust.
What is an example of a turboshaft engine used in helicopters?
Turbomeca Arriel 2C
What is required for the drive shaft inside the coupling to avoid carrying tension or compression loads?
Flexibility for the deflections caused by the transmission’s movements.
What is a key feature of modern coupling designs in turboshaft engines?
They are fail-safe and will show gradual and visible deterioration.
What does the power section of a turboshaft engine consist of?
- Additional stages of turbines
- Gear reduction system
- Shaft output
