15.17 Flashcards
What is a turbo shaft engine used for?
To drive machinery instead of producing thrust
What are common applications for turbsohaft engines?
APU, small lightweight engines, helicopters
Is the output shaft coupled directly to the engine turbine, or have a turbine of its own?
Both
What is a free turbine?
A shaft that is driven by its own turbine that rotates independently
What is the turbines output measured in?
Horsepower
What are the two things that make up a turbo shaft engine?
Gas generator and power section
How does the gas generator drive the power section?
By hot expanded gases
Where are turboshaft required to be used?
High power output, small and lightweight
Where is the reduction of engine RPM done in a turboshaft engine?
At the rear where where the power turbine drives the reduction gearbox and in tern drives the main accessory gearbox
Where is the reduction of engine RPM done in a turboshaft engine?
At the rear where where the power turbine drives the reduction gearbox and in tern drives the main accessory gearbox
What is the purpose of the drive system?
To transfer the power produced in the engine to the componente it drives
What is the purpose of the drive system?
To transfer the power produced in the engine to the components it drives
Due to high rotational speeds, what must be done to the rpm?
Reduced in the reduction gearbox then reduced further via the coupling shaft to the main rotor gearbox
In the Pratt and Whitney engine, there is two engines connected to a common gearbox. What is a freewheel unit used for?
To automatically disconnecf the slower engine
What is the freewheel unit made from?
A sprag clutch
What does the universal joint fit?
The shaft and the engine gearbox
What does the universal joint do?
Absorbs low amplitude oscillations
Ensures alignment between gearbox and shaft
Opposes engines torque reaction only allowing the transmission of torque
Why is reduction gearboxes used in an engine?
To slow down the output shaft
What is the main use for universal joints?
To ensure adequate movements of the transmission can take place
Why must the housing be flexible?
For deflections caused by transmission movements
What loads must the drive shaft not endure?
Compression or tension loads so will show gradual distortion
What safety design do couplings have?
Fail safe so show gradual distortion
What safety factors must you take into account when enduring power?
RPM and TIT
What is adjusted when you want to increase/decrease power?
Fuel flow
What 3 indications are there on FADEC controlled computers?
OFF - sends a signal to shut down or abort start sequence in case of abnormality
IDLE - engine runs at idle speed
FLIGHT - engine runs at full speed. Power requirements managed by FADEC increasing fuel consumption
