Part-66 Module 15 practice test

Question 1

A jet engine accelerates 100 kg/s of air from 200 m/s to 500 m/s. What is the net thrust (ignoring fuel mass and pressure thrust)?

Accepted Answer

30,000 N

Answer

50,000 N

Answer

20,000 N

Question 2

What is gross thrust?

Accepted Answer

Mass flow × jet velocity (plus any pressure thrust)

Answer

Total thrust minus the ram drag of the intake air

Answer

The thrust produced with the reversers deployed

Question 3

Why must the engine intake provide smooth, undistorted airflow to the compressor?

Accepted Answer

Distorted flow can cause compressor stall or surge

Answer

To reduce the temperature of the fuel in the pipes

Answer

To make the intake structure lighter and simpler

Question 4

What is the main advantage of a centrifugal compressor?

Accepted Answer

It is robust and gives a high pressure ratio per stage

Answer

It has the smallest frontal area

Answer

It gives the highest overall pressure ratio possible

Question 5

Which type of combustion chamber is used in most modern turbofan engines?

Accepted Answer

Annular

Answer

Multiple can

Answer

Reverse can only

Question 6

What is creep in turbine blades?

Accepted Answer

Slow permanent stretch under heat and centrifugal stress

Answer

Sudden fracture caused by impact from a foreign object

Answer

Corrosion caused by sulphur compounds in the fuel only

Question 7

What is the shape of the exhaust nozzle of a subsonic turbofan?

Accepted Answer

Convergent

Answer

Divergent

Answer

Convergent-divergent only

Question 8

Why are roller bearings used at some positions on engine shafts?

Accepted Answer

They carry radial load and allow thermal growth

Answer

They carry the large thrust loads of the spool

Answer

They seal oil inside the bearing chamber

Question 9

Why is oil consumption monitored?

Accepted Answer

A rise can show seal wear or leaks

Answer

To calculate passenger fares

Answer

Because oil is never consumed

Question 10

What is the main task of the engine fuel control unit (FCU) or FADEC fuel metering?

Accepted Answer

To meter fuel for the selected power within limits

Answer

To pump fuel from the aircraft tanks to the engine

Answer

To measure and display the fuel quantity in the tanks

Question 11

Why does a FADEC have two channels?

Accepted Answer

Redundancy: the standby channel takes over on failure

Answer

So that one FADEC can control two engines at the same time

Answer

To double the engine thrust available at take-off

Question 12

What is the engine's internal air system used for?

Accepted Answer

Cooling, sealing bearing chambers and balancing loads

Answer

Supplying passengers with oxygen in an emergency

Answer

Burning fuel in the primary zone of the combustor

Question 13

Which type of starter is most commonly used on large turbofan engines?

Accepted Answer

An air turbine starter

Answer

An electric starter-generator

Answer

A cartridge starter

Question 14

What does EPR stand for and what does it indicate?

Accepted Answer

Engine Pressure Ratio, indicating thrust

Answer

Exhaust Power Rating, indicating fuel flow

Answer

Engine Pump Ratio, indicating oil pressure

Question 15

How does an afterburner (reheat) increase thrust?

Accepted Answer

Burning extra fuel in the jet pipe behind the turbine

Answer

By increasing the compressor speed above its limit

Answer

By injecting water into the compressor inlet

Question 16

Why does a turboprop need a reduction gearbox?

Accepted Answer

The turbine runs far faster than the propeller should

Answer

To increase the propeller speed above engine speed

Answer

To reverse the engine rotation for ground taxiing

Question 17

What is the main purpose of an auxiliary power unit (APU)?

Accepted Answer

Electrical power and bleed air, mainly on the ground

Answer

Extra thrust for take-off from short runways

Answer

Pumping fuel between the tanks only

Question 18

What is the purpose of the engine firewall?

Accepted Answer

To separate the engine fire zone and contain a fire

Answer

To cool the engine compartment with ram air

Answer

To support the engine weight on the pylon

Question 19

Which type of fire detector gives warning along a continuous path through the engine compartment?

Accepted Answer

A continuous loop (or pneumatic) detector

Answer

A single thermal switch at one point

Answer

A smoke detector in the cabin

Question 20

What is a borescope used for in engine maintenance?

Accepted Answer

To inspect internal parts without disassembly

Answer

To measure the fuel quantity in the tanks

Answer

To balance the fan after blade replacement