Aircraft Design Questions and Answers – Propulsion Selection

This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Propulsion Selection”.

1. Which of the following is not an aircraft propulsion system?
a) High lift device
b) Reciprocating engine
c) Piston engine
d) Rocket engine
View Answer

Answer: a
Explanation: High lift devices are not part of aircraft propulsion system. High lift device is used to increase lift produced. Flaps are an example of high lift device which are used at takeoff and landing.

2. Which of the following is not the type of an aircraft propulsion?
a) Longerons
b) Air breathing propulsion
c) Non air breathing propulsion
d) Rocket engine
View Answer

Answer: a
Explanation: Longerons are structural elements of an aircraft. Longerons are heavy structural members that run straight and used to prevent bending.

3. Which of the following is an advantage of the piston prop engine?
a) Cheap and low fuel consumption
b) Highest speed
c) Supersonic speed always
d) Limited performance
View Answer

Answer: a
Explanation: Piston prop engine are widely used during early era. Piston prop engine provides cheap and low fuel consumption. Piston prop engine suffers from speed limits.

4. Which of the following is part of a turbine engine?
a) compressor
b) Flap
c) Aileron
d) Elevator
View Answer

Answer: a
Explanation: Compressor is an integral part of turbine engine. Flap is secondary control surface. Aileron and elevator are primary control surface. Aileron is used for rolling motion and elevator is used for pitching motion.

5. A typical turbine engine consists of __________
a) combustion chamber, turbine and compressor
b) only turbine
c) only compressor and turbine
d) turbine and combustion chamber only
View Answer

Answer: a
Explanation: A turbine engine is widely used engine in aviation sector. A typical turbine engine consists of following fundamental parts: Compressor, combustion chamber and turbine. Apart from this, most fighter aircrafts consist of afterburning section.

6. What is the function of a compressor?
a) To increase pressure and temperature
b) To increase velocity of flow
c) To expand flow
d) To generate work
View Answer

Answer: a
Explanation: Compressor is used to compress the flow. Compressor Increases pressure and temperature of the flow flowing through it. Due to increase in pressure, velocity of the flow reduces. Flow expansion can be achieved through nozzle.

7. What is the use of Turbine?
a) Generate work to drive shaft
b) To compress the flow
c) To increase pressure
d) To increase temperature
View Answer

Answer: a
Explanation: Turbine is an essential component of gas turbine engine. Turbine is used to decrease temperature and pressure of the gas. Combustion products pressure is reduced by turbine. Turbine generates work to drive the shaft.

8. Which of the following is correct?
a) Compressor consumes work produced by turbine
b) Compressor produces work to drive shaft
c) Compressor increases velocity of the flow
d) Lift is always same as weight
View Answer

Answer: a
Explanation: Turbine generates work to drive the shaft. This work is consumed to drive compressor. Compressor doesn’t produce work. Lift is not always same as weight. Compressor is used to increase pressure and temperature.

9. Which of the following is a type of compressor?
a) Centrifugal compressor
b) Incline compressor
c) Flap
d) Rudder compressor
View Answer

Answer: a
Explanation: Centrifugal Compressor is type of compressor. Centrifugal compressor uses centrifugal force to fling the air. Flow does not coincide with axis of rotation. Flap is secondary control surface of an aircraft.

10. Following diagram represents __________
a) piston prop
b) turboprop
c) turbojet
d) rocket
View Answer

Answer: a
Explanation: Piston prop engine is shown in above diagram. A typical piston prop engine relies piston and propeller blades to generate useful work and thrust. They are heavy and produces more noise.

11. Following diagram represents ___________
a) turbojet engine with centrifugal compressor
b) piston engine
c) piston prop aircraft
d) turboprop design
View Answer

Answer: a
Explanation: A typical Turbojet with centrifugal compressor is shown in above schematic diagram. Centrifugal force is used as working principle to drive this type of compressor. As shown in figure, it consists of combustion chamber and turbine stage as well.

12. Following diagram represents ___________
a) typical turbo jet
b) turbofan
c) turboprop
d) reciprocating
View Answer

Answer: a
Explanation: As shown in figure, a typical Turbojet engine is shown. Here, turbojet engine is operated by axial flow Compressor as shown in the above schematic diagram. As air passes through Compressor, pressure will increase and then it will be directed to combustion and preceding stages.

13. Following diagram represents ___________
a) turboprop
b) rocket
c) ramjet
d) scramjet
View Answer

Answer: a
Explanation: A turboprop is different from traditional piston prop engine. Here, propeller is connected to turbine engine via gear box. Rocket is type of aircraft and spacecraft propulsion system.

14. Following diagram represents ___________
a) turbofan
b) turbojet
c) piston engine
d) to and fro engine
View Answer

Answer: a
Explanation: A typical turbofan engine is shown in the above diagram. Turbofan operates with same principle as other has turbine engine. However, it has a fan mounted at inlet as shown. Fuel Efficiency of such engine is more than typical Turbojet.

15. Following diagram represents ___________
a) typical speed limit chart of propulsion system
b) drag polar
c) lift curve slope
d) lift coefficient variation
View Answer

Answer: a
Explanation: Above diagram is used to show the typical speed limit chart of current propulsion system in aviation. As shown turboprop and piston prop cannot be used for speeds beyond Mach 1. Lift curve slope is defined as change in lift coefficient per change in angle of attack.

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