Engines Ch.5

Front 1

Describe the basic construction of a turboprop engine.

Back 1

couples a gas generator with a reduction gear box and propeller, which is driven by the turbine section.

Front 2

Explain how a turboprop produces thrust.

Back 2

The propeller, which provides the majority of the thrust, imparts a small amount of acceleration to a large mass of air.

Front 3

Define the major components of the propeller assembly.

Back 3

blades: installed into the hub
hub: (barrel assembly) attaches to propeller shaft
pitch change/dome assembly: the mechanism that changes the blade angle of the propeller.

Front 4

Describe the purpose and operation of the reduction gear box used on a turboprop engine.

Back 4

Prevents the propeller blades from reaching supersonic speeds. It converts the high RPM and low torque of the gas generator to low rpm, high torque necessary for efficient propeller operation.

Front 5

Describe the major components and their operation of the torquemeter assembly

Back 5

Torque Shaft: coupled to the compressor by the compressor extension shaft. The other end of the torque shaft is connected to the reduction gear box. This shaft carries the load from the propeller and produces the torsional deflection. The reference shaft(outer shaft) is rigidly connected to the torque shaft at the compressor extension shaft. The other end is not rigidly connected. The reference shaft does not twist and therefore provides the reference to the twisting torque shaft.

Front 6

State the two main ways the propeller assembly may be connected to a gas generator

Back 6

1)attached to the front of the compressor drive shaft
2)attached to the free/power turbine

Front 7

Describe the operation and characteristics of a turboprop engine

Back 7

turboprop accelerates a very large mass of air with its propeller to a moderate speed.

Front 8

Describe alpha range and beta range operations of the propeller

Back 8

Alpha: (flight range) the PCL can be positioned from flight idle to full power.
Beta: ground operations. PCL from flight idle to max reverse.

Front 9

Describe the construction of a turboshaft engine.

Back 9

Gas generator and free/power turbine sections

Front 10

Describe the operation of the free/power turbine section.

Back 10

mechanically independent from the gas generator. Exhaust gases from the gas generator turbine drive the power turbine. This power turbine is connected to the main transmission through a coaxial main drive shaft. The main drive shaft can be located on the rear or front of the engines.

Front 11

Explain how the turboshaft produces thrust.

Back 11

Propulsive energy from the exhaust is negligible; that is, all of the remaining energy is extracted by the free or power turbine to drive the rotor assembly. In the turboshaft engine, virtually all of the pressure energy is converted into shaft horsepower.