15.17 - Turbo-shaft Engines Flashcards
What is the MRG?
The main reduction gearbox
What type of gears are usually used in the MRG?
Epicyclic gears
What is the purpose of the freewheel unit on a helicopter?
Prevents the rotor from driving the engine. They are always automatic units.
What is the most common used freewheel unit in helicopters?
The sprag clutch
How does a sprag clutch work?
It only allows rotation in one direction. The sprags are spring loaded and placed slightly on an angle
What is the Thomas coupling?
The most common type of disc coupling. (Connecting the power unit to the main rotor gearbox)
It is a ‘flexible’ coupling that allows for vibration and slight misalignment.
Where would you find the K-flex coupling?
Between the freewheeling unit and the gearbox. It has 3 rectangular plates which allow for angular misalignment and length changes. It also has a fail safe feature
What happens to the rotor angle of attack when the side collective stick is raised?
The angle of attack increases
What is the purpose of the free turbine governor?
It acts as a constant speed unit, giving constant output RPM throughout all flight conditions. It uses a flyweight-controlled governor.
What is the purpose of the beeper system?
It allows the pilot to set a new datum for the free turbine governor. It lets the pilot select extra power due to the free turbine not fully compensating to the load changes.
What is a curvic coupling?
It accurately aligns the driving and driven shafts
What two types of torquemeters are used on turboshaft engines?
Electro-mechanical and oil
