Aerospace Engineering MCQ Quiz - Objective Question with Answer for Aerospace Engineering - Download Free PDF

Latest Aerospace Engineering MCQ Objective Questions

Aerospace Engineering Question 1:

The resistance generated by air to the movement of the vehicle with N speed is proportional to?

Answer (Detailed Solution Below)

Aerospace Engineering Question 1 Detailed Solution

Aerodynamic Drag Force:

A vehicle traveling at a particular speed in air encounters a force resisting its motion. This force is known as aerodynamic drag.

The aerodynamic drag force (F) is given by:

where C d is the non-dimensional drag coefficient, A is the projected frontal area of the vehicle, ρ is the density of the surrounding air and V is the velocity of the flow.

Therefore, Drag force (F) ∝ V 2

In the given question V = N

Therefore, Drag force (F) ∝ N 2

The drag of the vehicle is therefore determined by its frontal area A, and by its shape, the aerodynamic quality of which is described by drag coefficient C d . Generally, the vehicle size and hence frontal area A is determined by the design requirements, and efforts to reduce drag are concentrated on reducing the drag coefficient.

Additional Information

The factor that affects the aerodynamics:

The shape of the object

• Geometry has a large effect on the aerodynamic forces generated by an object.
• Lift and drag depend linearly on the size of the object moving through the air.
• The cross-sectional shape of an object determines the form of drag created by the pressure variation around the object.
• If we think of drag as aerodynamic friction, the amount of drag depends on the surface roughness of the object; a smooth, waxed surface produces less drag than a roughened surface. This effect is called skin friction and is usually included in the measured drag coefficient of the object.
• In the case of a car having a tapering front /head, This streamlined shape is given to reduce the fluid (Air) friction.
• The streamlined shape helps to overcome the friction between objects and fluids.

Aerospace Engineering Question 2:

1. to increase maximum drag
2. to increase maximum lift
3. to decrease maximum lift
4. to decrease maximum drag

Answer (Detailed Solution Below)

Aerospace Engineering Question 2 Detailed Solution

Explanation:

Camber

• Camber is the maximum deviation of the camber line (which is the bisector of the profile thickness) from the chord of the profile, as shown in the figure.

Effect of the maximum camber and its position

• Under normal circumstances, if the camber is increased, the maximum lift coefficient will be increased, particularly if the leading edge radius is small or the airfoil is thin.
• However, with increasing camber, the increase in the lift coefficient becomes slow, and the drag coefficient increases at the same time.
• And the increments of drag coefficients are different with different airfoils.
• Further, when the position of the maximum camber is further forward, the maximum lift coefficient becomes large.

Aerospace Engineering Question 3:

Answer (Detailed Solution Below)

Aerospace Engineering Question 3 Detailed Solution

Explanation:

Canard

• Canard is a French word for duck, which in flight stretches out its long neck with its bulbous head in front.
• When a horizontal surface is placed in front of the aircraft, it presents a similar configuration; hence, this surface is sometimes called a Canard.
• A canard is an aerodynamic arrangement wherein a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft.
• The term "Canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane.

Aerospace Engineering Question 4:

1. Flaps
2. Rudder
3. Spoiler
4. Elevator

Answer (Detailed Solution Below)

Aerospace Engineering Question 4 Detailed Solution

Explanation:

• The yaw axis is defined to be perpendicular to the plane of the wings with its origin at the center of gravity and directed towards the bottom of the aircraft.
• A yaw motion is a movement of the nose of the aircraft from side to side.
• The pitch axis is perpendicular to the yaw axis and is parallel to the plane of the wings with its origin at the center of gravity and directed towards the right wing tip.
• A pitch motion is an up or down movement of the nose of the aircraft.
• The roll axis is perpendicular to the other two axes with its origin at the center of gravity and is directed towards the nose of the aircraft.
• A rolling motion is an up and down movement of the wingtips of the aircraft.
  • Elevator controls pitching motion.
  • Rudder controls yawing motion.
  • Ailerons control rolling motion.

  

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  Aerospace Engineering Question 5:

  The following type of aircraft requires the longest runway for take-off
  
  1. the aircraft that uses turboprop
  2. the aircraft that uses turbojet
  3. the aircraft that uses piston engine
  4. the aircraft that uses turbofan

  Answer (Detailed Solution Below)

  Option 2 : the aircraft that uses turbojet

  Aerospace Engineering Question 5 Detailed Solution

  A group of turbo-engines such as turbojet, turbofan and turbo propeller engines are classified as a gas turbine or simply turbine engines in which a turbine is used to produce shaft power.

  An aircraft gas turbine engine is a device in which free stream air is taken in through an inlet, compressed in a rotating compressor, heated in the combustion chamber and expanded through a turbine.

  The gas then leaves the nozzle at a velocity much greater than the free stream.

  The reaction to the ejection of this mass of gas is the forward force on the engine and aircraft (thrust).

  The amount of force or thrust produced depends on the amount of mass of air moved through the engine per unit time (i.e., mass ow rate) and the extent to which this air can be accelerated.

  A small percentage of this power output of the turbine is utilized to drive the turbine/compressor and any mechanical load, such as electrical generators and hydraulic pumps, connected to the drive shaft.

  The gas turbine engine can be used in several configurations, some of which are discussed below.

  

  • A pure gas turbine engine that generates thrust through its nozzle is called a turbojet engine.
  • An aircraft which has turbojet engine required long runway for take-off.
  • A turbojet is a gas turbine engine in which no excess power (above that required by the compressor) is supplied to the shaft by the turbine.
  • The available energy in the exhaust gases is converted to the kinetic energy of the jet through its nozzle (i.e. thrust).
  • In a turbojet engine, the energy that is added to the air by a compressor (high pressure) and by a combustion chamber (high temperature) is divided into two parts.
  • One part returns back to the compressor and the other one goes to the nozzle. The energy that is supposed to be transferred into the compressor is first absorbed by the turbine and converted into mechanical energy.
  • Thus, all the mechanical energy that is produced by the turbine is transferred into the compressor via a shaft to increase the incoming air pressure.
  • The remaining energy of the high-temperature, high-pressure air is transferred into the nozzle.

  

  • A turbofan engine is a modified version of a turbojet in which the turbine extracts gas power in excess of that required to drive a fan or low-pressure compressor in a fan (auxiliary) duct, usually annular around the primary duct (core).
  • The turbofan engine imparts momentum to a greater volume of air than a turbojet, but the velocity added is less.
  • Basically, a turbojet engine forms the core of the turbofan; the core contains the inlet, compressor, burner, turbine, and nozzle.
  • However, in the turbofan engine, the turbine drives not only the compressor but also a large fan external to the core.
  • The flow through a turbofan engine is split into two paths.
  • One airflow passes through the fan and flows externally over the core; this air is processed only by the fan.
  • The thrust obtained from this ow through the fan is generated with an efficiency similar to that of a propeller.
  • The second airflow passes through the core itself.
  • The thrust obtained from the flow through the core is generated with an efficiency associated with a turbojet.
  • The overall propulsive efficiency of a turbofan engine is, therefore, a compromise between that of a propeller and that of a turbojet.
  • In addition, the noise of a turbofan engine is much lower than that of a turboprop engine.

  

  • A turboprop is a gas turbine engine in which the turbine absorbs power in excess of that needed to drive the compressor.
  • The excess power is used to drive a propeller .
  • Although most of the energy in the hot gases is absorbed by the turbine, the turboprop engine still has slight jet thrust generated by the exhaust gas in its nozzle.
  • Thus, most of the gas energy is extracted by the turbine to drive the propeller.
  • Here, similar to the turbojet, the inlet air is compressed by an axial-flow compressor, mixed with fuel and burned in the combustor, expanded through a turbine, and then exhausted through a nozzle.
  • However, unlike the turbojet, the turbine powers not only the compressor but also the propeller.
  • A major problem with the turboprop engine is the very loud noise, which makes it undesirable for carrying passengers.

  

  • A gas turbine engine that delivers power through a shaft to operate something other than a propeller is referred to as a turboshaft engine.
  • Turboshaft engines are very similar to turboprop engines. The turbine that extracts energy from the gas flow is primarily designed to produce shaft power.
  • The turboshaft engine has the same basic components found in a turbojet engine, with the addition of a turbine shaft to absorb the power of the hot gases of combustion.

  

  • I n high supersonic speeds (Mach numbers beyond 3), a new type of jet engine, Ramjet, is more efficient than a turbojet and turbofan engines.
  • The ramjet engine has a simple structure and has no moving part (no turbine).
  • A ramjet is basically a duct with the front end shaped to be the inlet, the aft end designed as a nozzle, and the combustion chamber in the middle.
  • This type of engine is using the engine’s forward motion to compress incoming air.
  • Since the high-speed flow has a high stagnation pressure, this pressure will be converted to static pressure in the inlet duct in a slowdown process.
  • Located in the combustion chamber are flame holders, fuel injection nozzles, and an igniter.
  • The main drawback of the ramjet engine is that it is initially assisted to accelerate and attain a velocity in excess of about Mach 0.5 before it can be self-sufficient .
  • Once this speed is reached, there is sufficient combustion pressure to continue firing the engine.
  • The flame holders located in the combustion chamber provide the necessary blockage in the passage to slow down the airflow so that the fuel and air can be mixed and ignited.
  • The combustion product is then passed through a nozzle to accelerate it to supersonic speeds.
  • This acceleration generates forward thrust.
  • For a supersonic flight Mach number, acceleration is typically achieved via a convergent-divergent nozzle.