# Aircraft Propulsion - MCQs with Answers

## Aircraft Propulsion - MCQs with Answers

Q1. Gas turbines are suitable for aircraft propulsion because

a. gas turbines are light weight
b. gas turbines are compact in size
c. gas turbines have a high power-to-weight ratio
d. all of the above

ANSWER: d. all of the above

Q2. Which among the following engines is NOT the type of aircraft gas turbine which works on jet propulsion cycle?

a. turbojet
b. turbofan
c. turboprop
d. none of the above

ANSWER: d. none of the above

Q3. In working condition of turbojet engine, velocity of air entering the engine is

a. higher than the velocity of exhaust gases leaving the engine
b. lower than the velocity of exhaust gases leaving the engine
c. equal to the velocity of exhaust gases leaving the engine
d. cannot say

ANSWER: b. lower than the velocity of exhaust gases leaving the engine

Q4. Why do the airplanes fly at higher altitude during the long flights?

a. to avoid collisions as they are at very high speed and controlling will be difficult if something (like towers, hills) comes in the way
b. it is easy to communicate with satellites at high altitudes
c. to save the fuel as air at higher altitude exerts smaller drag force on aircraft
d. none of the above

ANSWER: c. to save the fuel as air at higher altitude exerts smaller drag force on aircraft

Q5. The propulsive power developed by the thrust of engine is given by

a. mair (Vexit – Vinlet)
b. mair (Vexit – Vinlet) × Vaircraft
c. (Vexit – Vinlet) × Vaircraft
d. none of the above

ANSWER: b. mair (Vexit – Vinlet) × Vaircraft

Q6. The propulsive efficiency is the ratio of

a. the propulsive power to the energy input rate
b. the exit velocity rate of exhaust gases to the energy input rate
c. the work done by the turbine to the energy input rate
d. velocity of aircraft to the energy input rate

ANSWER: a. the propulsive power to the energy input rate

Q7. In turbofan engine, fan is used

a. to compress the inlet air more efficiently
b. to increase the total thrust of the engine
c. both a. and b
d. none of the above

ANSWER: b. to increase the total thrust of the engine

Q8. In turbofan engine, the bypass ratio is the ratio of

a. total mass flow rate of exhaust stream to the mass flow rate of stream from turbine exhaust
b. total mass flow rate of exhaust stream to the mass flow rate of stream from fan exhaust
c. the mass flow rate of stream from turbine exhaust to the mass flow rate of stream from fan exhaust
d. the mass flow rate of stream from fan exhaust to the mass flow rate of stream from turbine exhaust

ANSWER: d. the mass flow rate of stream from fan exhaust to the mass flow rate of stream from turbine exhaust

Q9. What is the effect of increasing bypass ratio of a turbofan engine on its trust?

a. trust increases with increase in bypass ratio of turbofan engine
b. trust decreases with increase in bypass ratio of turbofan engine
c. trust of the turbofan engine only depends upon the fuel rate, so no change of thrust with increase in bypass ratio
d. cannot say