15.1 MCQ

Question 1

In the dual axial-flow or twin spool compressor system, the first stage turbine drives the
a) N1 compressor
b) N1 and N2 compressors
c) N2 compressor

Answer 1

c) N2 compressor

Question 2

A by-pass engine LP compressor

a) supplies only the required quantity of combustion
b) supplies less air than is required for combustion
c) supplies more air than is required for combustion

Answer 2

c) supplies more air than is required for combustion

Question 3

A bypass ratio of 5:1 indicates that the bypass flow is
a) equal to 1/5 of the hot stream
b) five times the cold stream
c) five times the hot stream

Answer 3

c) five times the hot stream

Question 4

A free turbine is usually found on a
a) Turbo-jet
b) Turbo- fan
c) Turbo prop

Answer 4

c) Turbo prop

Question 5

A high bypass engine results in
a) lower propulsive efficiency
b) overall faster airflow
c) overall slower airflow and greater propulsive efficiency

Answer 5

c) overall slower airflow and greater propulsive efficiency

Question 6

A jet engine derives its thrust by
a) drawing air into the compressor
b) impingement of the propelling gases on the outside air
c) reaction of the propelling gases

Answer 6

c) reaction of the propelling gases

Question 7

A method of comparing engine efficiencies is by comparing

a) thrust to weight ratio
b) fuel consumption
c) specific fuel consumption

Answer 7

c) specific fuel consumption

Question 8

A nozzle is ‘choked’ when the gas flow or air flow at the throat is
a) subsonic
b) Transonic to supersonic/sonic
c) hypersonic

Answer 8

b) Transonic to supersonic/sonic

Question 9

A powerplant consists of

a) a basic engine plus E.C.U
b) the complete engine as it would be found on aircraft including all connections, controls, cowlings, intake etc
c) a basic engine plus thrust reverser, exhaust system and gear box with accessories

Answer 9

b) the complete engine as it would be found on aircraft including all connections, controls, cowlings, intake etc

Question 10

A turbo jet engine gives
a) small acceleration to a large mass of air
b) large acceleration to a small mass of air
c) large acceleration to a large weight of air

Answer 10

b) large acceleration to a small mass of air

Question 11

A turbo-shaft engine has

a) a mechanical connection between compressor and turbine
b) none of the above
c) the power shaft is not connected to the compressor

Answer 11

a) a mechanical connection between compressor and turbine

Question 12

An advantage of a centrifugal compressor is
a) it is unaffected by turbulence
b) it is dynamically balanced
c) it is robust and can stand some shock from ‘icing up

Answer 12

c) it is robust and can stand some shock from ‘icing up

Question 13

As subsonic air flows through a convergent nozzle the velocity
a) increases
b) decreases
c) remains constant

Answer 13

a) increases

Question 14

Bernoulli’s Theorem states that at any point in a flow of gas
a) the static pressure is less than the dynamic pressure
b) the static pressure and dynamic pressure are equal
c) the total energy remains constant

Answer 14

c) the total energy remains constant

Question 15

Engine thrust varies with temperature

a) low temperature gives greater mass flow and therefore greater thrust
b) low temperatures give low thrust
c) increase in temperature gives greater thrust because of low friction in compressors

Answer 15

a) low temperature gives greater mass flow and therefore greater thrust

Question 16

In a choked nozzle velocity has increased to max and
a) density decreases
b) pressure decreases
c) pressure has increase

Answer 16

c) pressure has increase

Question 17

In a free turbine
a) there is a direct drive with a free-wheel unit
b) there is no mechanical connection with the components
c) there is a clutch between compressor and power output shaft

Answer 17

b) there is no mechanical connection with the components

Question 18

In a turbo jet engine, combustion occurs at
a) constant velocity
b) constant volume
c) constant pressure

Answer 18

c) constant pressure

Question 19

Increasing ram effect with increased speed
a) reduces thrust due to reduced turbine temperature
b) increases thrust due to increased maximum airflow
c) reduces thrust due to reduced compressor efficiency

Answer 19

b) increases thrust due to increased maximum airflow

Question 20

On an axial flow, dual compressor forward fan engine, the fan turns the same speed as the

a) high pressure compressor
b) low pressure turbine
c) forward turbine wheel

Answer 20

b) low pressure turbine

Question 21

Ram effect” due to aircraft forward speed will cause the efficiency of the engine to
a) remain constant
b) increase
c) decrease

Answer 21

b) increase

Question 22

The efficiency of a gas turbine engine at high altitude

a) decreases (note: engine aircraft combination as in our system)
b) increases (engine theory only)
c) remains constant

Answer 22

a) decreases (note: engine aircraft combination as in our system)

Question 23

The forces driving most turbines around are due to
a) reaction only
b) impulse only
c) impulse and reaction

Answer 23

c) impulse and reaction

Question 24

The stator vanes in an axial-flow compressor

a) convert velocity energy into pressure energy
b) convert pressure energy onto velocity energy
c) direct air into the first stage rotor vanes at the proper angle

Answer 24

a) convert velocity energy into pressure energy

Question 25

The symbol for designating the speed of a single compressor engine is
a) N.G (gas generator Nf free turbine)
b) N
c) N1

Answer 25

c) N1

Question 26

The working fluid of a gas turbine engine is
a) air
b) gasoline
c) kerosene

Answer 26

a) air

Question 27

Thrust
a) increases with high temperature
b) decreases with low temperature
c) increases with low temperature

Answer 27

c) increases with low temperature

Question 28

What purpose do the diffuser vanes of a centrifugal compressor serve?

a) To convert kinetic energy into pressure energy
b) To increase the air velocity.
c) To convert pressure energy into kinetic energy.

Answer 28

a) To convert kinetic energy into pressure energy

Question 29

When a volume of air is compressed
a) no heat is lost or gained
b) heat is lost
c) heat is gained

Answer 29

c) heat is gained