15.16 Turboprop Engines

Question 1

What is the most efficient speed range of turboprop engines?

Answer 1

300-450mph

Question 2

What type of engine provides the best specific fuel consumption?

Answer 2

Turboprops

Question 3

What happens to the propulsive efficiency of a turboprop as airspeed increases?

Answer 3

Remains constant

Question 4

What % of total power can a turboprop extract?

Answer 4

95%

Question 5

What type of turboprop engine has no mechanical connection between the gas generator and power turbine?

Answer 5

Gas-coupled/free-power turbine

Question 6

What is the function of the gas generator?

Answer 6

Produces high velocity gases that provide energy to drive the power turbine

Question 7

What do gear/direct-coupled engines have which remains mechanically connected to the compressor and reduction gearbox?

Answer 7

Extra turbine discs

Question 8

What is the core engine known as in a turboprop engine?

Answer 8

Gas generator

Question 9

What is required in a gear/direct-coupled turbine to adjust the propeller pitch for power requirements?

Answer 9

A complex integrated propeller control system

Question 10

What is the function of the reduction gear assembly on a turboprop?

Answer 10

Reduces high rpm from engine to a propeller rpm that won’t exceed maximum propeller tip speed

Question 11

What are the 2 types of reduction gears?

Answer 11

Parallel spur and epicyclic

Question 12

What are the reduction gears made of?

Answer 12

Alloy steel forgings

Question 13

How is the reduction gear ratio calculated on epicyclic gears?

Answer 13

Driven teeth divided by number of driving teeth

Question 14

What are the types of parallel spur gears?

Answer 14

Straight cut and helical

Question 15

What is a disadvantage and advantage of straight cut gears?

Answer 15

Have the lowest frictional losses but noisy

Question 16

What is alpha range?

Answer 16

In flight

Question 17

What is beta range?

Answer 17

Ground handling and reversing

Question 18

What is the function of the spinner assembly?

Answer 18

Reduces drag

Question 20

What does the turboprop control assembly feathering system do?

Answer 20

Feathers the propeller when the engine is shutdown in flight

Question 21

What control lever does a gear-coupled engine have?

Answer 21

Single-lever control

Question 22

What control lever does a free-turbine engine have?

Answer 22

Dual-lever control

Question 23

What happens when you move a single power lever forward?

Answer 23

Fuel flow increases and a higher rpm selected

Question 24

What is the difference between the dual control lever and single control lever?

Answer 24

Fuel/power control and propeller control is interconnected on a single lever control

Question 25

What is the function of a control lock?

Answer 25

Ensures aircraft control surfaces don’t flutter on the ground when engines are running

Question 26

What range does the propeller lever operate in?

Answer 26

Constant speed range

Question 27

What does the power lever do?

Answer 27

Schedules fuel flow from idle to take off range

Question 28

How is the blade angle change mechanism operated?

Answer 28

Hydraulically, using engine oil

Question 29

What is the function of the automatic drag limiting system (ADLS)?

Answer 29

Feathers (coarse pitch) the blades to avoid windmilling if the oil supply fails.

Question 30

When will an over speed propeller governor dump oil pressure to the return?

Answer 30

If propeller speed exceeds 105%

Question 31

When is a propeller over speed governor used?

Answer 31

If the normal propeller governor and fuel control over speed governor fail to contain engine speed

Question 32

What is the function of the PCU?

Answer 32

Governs the maximum rpm of the engine