# Volume 2 - 2014 2A651 CDC

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Questions and Answers
• 1.

### (201) An aircraft taxiing at a steady speed can be used to demonstrate

• A.

Bernoulliâ€™s principle.

• B.

Newtonâ€™s first law of motion.

• C.

Newtonâ€™s second law of motion.

• D.

Newtonâ€™s third law of motion.

Correct Answer
B. Newtonâ€™s first law of motion.
Explanation
When an aircraft is taxiing at a steady speed, it demonstrates Newton's first law of motion, also known as the law of inertia. According to this law, an object at rest or in motion will continue to stay in that state unless acted upon by an external force. In this case, the aircraft will continue to move at a steady speed unless a force, such as braking or engine power, is applied to change its motion. This demonstrates the principle of inertia, which is a fundamental concept of Newton's first law of motion.

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• 2.

### (201) Newton’s third law of motion explains why an operating jet engine produces

• A.

Forward thrust.

• B.

Forward acceleration.

• C.

Increased acceleration.

• D.

Decreased acceleration.

Correct Answer
A. Forward thrust.
Explanation
Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the case of an operating jet engine, the action is the expulsion of high-speed exhaust gases from the rear of the engine. The reaction to this action is the forward thrust generated by the engine. As the exhaust gases are expelled with a high velocity in one direction, the engine experiences an equal and opposite force in the opposite direction, propelling the aircraft forward. Therefore, the correct answer is forward thrust.

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• 3.

### (201) Which type of duct would decrease the velocity and increase the pressure of a gas as it passes through?

• A.

Elbow.

• B.

Straight.

• C.

Divergent.

• D.

Convergent.

Correct Answer
C. Divergent.
Explanation
A divergent duct is designed to gradually increase in size, causing the gas to expand and slow down as it passes through. This decrease in velocity leads to an increase in pressure. Therefore, a divergent duct would decrease the velocity and increase the pressure of a gas as it passes through.

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• 4.

### (201) "The combination of decreased pressure above an airfoil, and the increased pressure below the airfoil produces lift" is best described by

• A.

Bernoulliâ€™s principle.

• B.

Newtonâ€™s first law of motion.

• C.

Newtonâ€™s second law of motion.

• D.

Newtonâ€™s third law of motion.

Correct Answer
A. Bernoulliâ€™s principle.
Explanation
The statement describes the phenomenon of lift production on an airfoil, which is best explained by Bernoulli's principle. According to Bernoulli's principle, as the velocity of a fluid (in this case, air) increases, its pressure decreases. This principle applies to the flow of air over an airfoil, where the increased velocity of air above the curved upper surface creates a lower pressure compared to the slower-moving air below the airfoil. This pressure difference generates an upward force, known as lift, which allows the airfoil (such as an airplane wing) to generate upward motion.

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• 5.

### (202) Foot-pounds and inch-pounds are units of measure for

• A.

Work.

• B.

Power.

• C.

Inertia.

• D.

Friction.

Correct Answer
A. Work.
Explanation
Foot-pounds and inch-pounds are units of measure for work because work is defined as the product of force and distance. In this case, the force is measured in pounds and the distance is measured in feet or inches. Work is the amount of energy transferred when a force is applied over a distance, so foot-pounds and inch-pounds are appropriate units for measuring work.

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• 6.

### (202) What does fuel for an engine represent?

• A.

Available horsepower.

• B.

Thrust produced.

• C.

Potential energy.

• D.

Efficiency ratio.

Correct Answer
C. Potential energy.
Explanation
Fuel for an engine represents potential energy. When fuel is burned in the engine, it releases energy in the form of heat, which is then converted into mechanical energy to power the engine. This potential energy stored in the fuel is what allows the engine to perform work and generate power.

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• 7.

### (203) Which section of a jet engine continually supplies air and maintains pressure?

• A.

Turbine.

• B.

Diffuser.

• C.

Compressor.

• D.

Combustion.

Correct Answer
C. Compressor.
Explanation
The compressor section of a jet engine continually supplies air and maintains pressure. The compressor takes in air and compresses it before sending it to the combustion chamber. This compressed air is essential for the combustion process and provides the necessary pressure for efficient combustion and thrust generation in the engine.

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• 8.

### (203) The temperature of compressed air in a jet engine must be raised to

• A.

Increase energy.

• B.

Decrease energy.

• C.

Increase volume.

• D.

Decrease volume.

Correct Answer
A. Increase energy.
Explanation
In a jet engine, the temperature of compressed air needs to be raised in order to increase the energy. This is because increasing the temperature of the air increases its kinetic energy, which in turn increases the energy available for propulsion and thrust. By raising the temperature, the air molecules move faster and collide with more force, resulting in a more powerful and efficient jet engine.

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• 9.

### (203) Which section of a jet engine introduces and burns fuel?

• A.

Turbine.

• B.

Diffuser.

• C.

Compressor.

• D.

Combustion.

Correct Answer
D. Combustion.
Explanation
The section of a jet engine that introduces and burns fuel is called the combustion section. In this section, fuel is mixed with compressed air and ignited, producing a high-temperature and high-pressure gas. This gas then expands and flows through the turbine, where it generates power to drive the compressor and other engine components. The combustion section is a critical part of the jet engine's operation, as it is responsible for converting the chemical energy in the fuel into mechanical energy that propels the aircraft forward.

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• 10.

### (204) How many British thermal units (Btu) does the heat content per pound of kerosene produce?

• A.

10,500.

• B.

15,000.

• C.

18,500.

• D.

40,000.

Correct Answer
C. 18,500.
Explanation
Kerosene has a heat content of 18,500 British thermal units (Btu) per pound. This means that when one pound of kerosene is burned, it releases 18,500 Btu of heat energy.

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• 11.

### (204) The efficiency of a jet engine is often referred to as

• A.

Energy.

• B.

Momentum.

• C.

Thermal efficiency.

• D.

Propulsive efficiency.

Correct Answer
C. Thermal efficiency.
Explanation
The efficiency of a jet engine is commonly measured in terms of thermal efficiency, which refers to the ratio of the useful work output (in this case, the propulsive power generated by the engine) to the energy input (the fuel burned). This measure indicates how effectively the engine converts the energy from the fuel into useful work, making it a suitable term to describe the efficiency of a jet engine. Energy and momentum are not specific measures of engine efficiency, while propulsive efficiency refers to the ratio of the useful work output to the energy flow through the engine, which is a different concept from thermal efficiency.

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• 12.

### (204) The product of thermal efficiency and propulsive efficiency is

• A.

Mechanical efficiency

• B.

Overall efficiency

• C.

Power efficiency

• D.

Thrust efficiency

Correct Answer
B. Overall efficiency
Explanation
The product of thermal efficiency and propulsive efficiency is overall efficiency. Thermal efficiency measures the effectiveness of converting thermal energy into useful work, while propulsive efficiency measures the effectiveness of converting the work done by the engine into useful thrust. Multiplying these two efficiencies together gives the overall efficiency, which represents the effectiveness of converting thermal energy into useful thrust. Therefore, overall efficiency is the correct answer.

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• 13.

### (205) To measure barometric pressure, you would use a

• A.

Potentiometer.

• B.

Potentiometer.

• C.

Pyrometer.

• D.

Barometer

Correct Answer
D. Barometer
Explanation
A barometer is the correct instrument to measure barometric pressure. A barometer is designed specifically for this purpose and is used to measure the atmospheric pressure in a given area. It consists of a sealed container filled with mercury or aneroid capsules that are sensitive to pressure changes. By measuring the height of the mercury column or the displacement of the capsules, the barometer can provide an accurate reading of the barometric pressure. A potentiometer is used to measure electrical potential difference, a pyrometer is used to measure high temperatures, and a barometer is used to measure barometric pressure.

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• 14.

### (205) What effect does moisture content or humidity have on density of air?

• A.

More moisture, more dense

• B.

More moisture, less dense

• C.

Less moisture, less dense

• D.

None.

Correct Answer
B. More moisture, less dense
Explanation
When there is more moisture in the air, it displaces some of the dry air molecules, resulting in a decrease in the overall density of the air. This is because water molecules are lighter than the average air molecule. Therefore, the correct answer is "More moisture, less dense."

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• 15.

### (205) Due to the divergent design of a diffuser, air pressure

• A.

Remains the same

• B.

Fluctuates.

• C.

Decreases.

• D.

Increases.

Correct Answer
D. Increases.
Explanation
The correct answer is "increases." In a divergent design of a diffuser, the cross-sectional area of the flow passage increases, causing the velocity of the air to decrease. According to Bernoulli's principle, as the velocity decreases, the pressure increases. Therefore, in a divergent diffuser, the air pressure increases.

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• 16.

### (205) The air temperature of a jet engine gradually rises across the compressor to the diffuser outlet as a result of

• A.

Compression.

• B.

Fuel expansion.

• C.

Turbine discharge.

• D.

Ambient temperature increase.

Correct Answer
A. Compression.
Explanation
The correct answer is compression. In a jet engine, the air temperature gradually rises across the compressor to the diffuser outlet. This is because the compressor compresses the incoming air, increasing its pressure and temperature. As the air is compressed, its molecules are forced closer together, resulting in an increase in temperature. This compressed and heated air is then used for combustion in the combustion chamber, leading to the generation of thrust in the engine.

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• 17.

### (205) Where is the highest point of temperature reached in an engine?

• A.

Tailpipe.

• B.

Exhaust cone.

• C.

Turbine section.

• D.

Combustion section.

Correct Answer
D. Combustion section.
Explanation
The highest point of temperature in an engine is reached in the combustion section. This is where the fuel is burned, generating a high amount of heat and energy. The combustion section is designed to withstand and control these high temperatures, ensuring efficient combustion and power generation in the engine.

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• 18.

### (206) Which engine component meters fuel for combustion?

• A.

Pressure and drain (P&D) valve.

• B.

Fuel control.

• C.

Fuel nozzle.

• D.

Fuel pump.

Correct Answer
B. Fuel control.
Explanation
The fuel control is the engine component that meters fuel for combustion. It regulates the flow of fuel into the engine based on the demand and operating conditions. It ensures that the correct amount of fuel is delivered to achieve optimal combustion and power output. The pressure and drain valve, fuel nozzle, and fuel pump are also important components in the fuel system, but they do not directly meter the fuel for combustion like the fuel control does.

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• 19.

### (206) What happens to the energy that is absorbed by the turbine wheel?

• A.

50 percent is used for accessories.

• B.

60 percent is used for accessories.

• C.

It is returned to the compressor.

• D.

It operates the anti-ice system.

Correct Answer
C. It is returned to the compressor.
Explanation
When the energy is absorbed by the turbine wheel, it is returned to the compressor. This is because the turbine wheel is connected to the compressor through a shaft, and the energy that is absorbed by the turbine wheel is used to drive the compressor. The compressor then pressurizes the air, which is essential for the proper functioning of the engine. Therefore, the energy absorbed by the turbine wheel is not wasted but rather recycled and used to power the compressor.

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• 20.

### (207) What is the required velocity for air and gases flowing through a jet engine?

• A.

Low velocity at all times.

• B.

Less velocity exiting than entering.

• C.

Equal velocity entering and exiting.

• D.

Greater velocity exiting than entering.

Correct Answer
D. Greater velocity exiting than entering.
Explanation
In a jet engine, the required velocity for air and gases is greater when exiting than when entering. This is because the engine works on the principle of thrust, which is generated by expelling a large volume of air at a high velocity. By increasing the velocity of the exhaust gases, the engine is able to produce a greater amount of thrust, allowing the aircraft to move forward. Therefore, the correct answer is greater velocity exiting than entering.

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• 21.

### (207) The velocity of the stream of air that flows through a jet engine reaches its highest point at the

• A.

Ejector nozzle.

• B.

Combustion section.

• C.

Turbine exhaust cone.

• D.

Turbine stator (nozzle diaphragm).

Correct Answer
A. Ejector nozzle.
Explanation
The correct answer is ejector nozzle. In a jet engine, the velocity of the air stream reaches its highest point at the ejector nozzle. This is because the ejector nozzle is specifically designed to accelerate the flow of air as it exits the engine, creating a high-velocity jet of air. The other options mentioned, such as the combustion section, turbine exhaust cone, and turbine stator, are not directly related to the highest velocity of the air stream in the engine.

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• 22.

### (207) What is the general flow of gases from the combustion chamber?

• A.

At right angles to the rotor shaft.

• B.

Parallel to the axis of the rotor shaft.

• C.

At the same velocity as the rotor shaft.

• D.

In a reverse direction from the rotor shaft.

Correct Answer
B. Parallel to the axis of the rotor shaft.
Explanation
The general flow of gases from the combustion chamber is parallel to the axis of the rotor shaft. This means that the gases flow in the same direction as the rotor shaft, creating a straight and consistent flow. This flow is important for the overall operation and efficiency of the system.

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• 23.

### (207) Gases enter the jet-engine’s first-stage turbine wheel blades from the

• A.

Turbine wheel blades.

• B.

Combustion chamber.

• C.

Turbine stator.

• D.

Flameholder.

Correct Answer
C. Turbine stator.
Explanation
The gases enter the jet-engine's first-stage turbine wheel blades from the turbine stator. The turbine stator is a stationary component located between the combustion chamber and the turbine wheel blades. Its purpose is to guide and direct the flow of gases towards the turbine wheel blades, where the energy from the gases is extracted to power the engine.

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• 24.

### (207) When two or more turbine wheels are used in a jet engine, which component is placed directly in front of each turbine wheel?

• A.

Diffuser.

• B.

Jet nozzle.

• C.

Combustion chamber.

• D.

Turbine stator (nozzle diaphragm).

Correct Answer
D. Turbine stator (nozzle diaphragm).
Explanation
When two or more turbine wheels are used in a jet engine, the component that is placed directly in front of each turbine wheel is the turbine stator (nozzle diaphragm). The turbine stator is responsible for directing the flow of exhaust gases onto the turbine blades, which in turn drives the turbine wheel. This component helps to optimize the efficiency and performance of the turbine system in the jet engine.

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• 25.

### (208) A jet engine derives its name from its design in that it uses

• A.

An exhaust-gas-driven turbine wheel to drive its compressor.

• B.

Nozzles which are called jet within the engine.

• C.

A turbine-type compressor to maintain power.

• D.

Turbo-superchargers within the engine.

Correct Answer
A. An exhaust-gas-driven turbine wheel to drive its compressor.
Explanation
A jet engine gets its name from its design because it utilizes an exhaust-gas-driven turbine wheel to drive its compressor. This means that the turbine wheel is powered by the exhaust gases produced by the engine, which in turn drives the compressor to provide the necessary airflow for combustion and propulsion. This design is a key characteristic of jet engines and distinguishes them from other types of engines.

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• 26.

### (208) A turbo-supercharger is essentially a

• A.

Jet engine.

• B.

High-capacity air pump.

• C.

Temperature reduction device.

• D.

High-volume air direction device.

Correct Answer
B. High-capacity air pump.
Explanation
A turbo-supercharger is essentially a high-capacity air pump. It is a device that increases the air pressure and density entering the engine, which in turn increases the amount of oxygen available for combustion. This results in improved engine performance and power output. The turbo-supercharger achieves this by using a turbine to harness the energy from the engine's exhaust gases and drive a compressor that compresses the incoming air. Therefore, the turbo-supercharger acts as a high-capacity air pump, supplying more air to the engine for improved performance.

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• 27.

### (209) The two forces that air is subjected to after it is drawn into the guide vanes of a centrifugal compressor are

• A.

Rotational and centrifugal.

• B.

Tangential and centrifugal.

• C.

Rotational and tangential.

• D.

Tangential and radial.

Correct Answer
A. Rotational and centrifugal.
Explanation
After air is drawn into the guide vanes of a centrifugal compressor, it is subjected to two forces: rotational and centrifugal. The rotational force refers to the circular motion of the air as it moves through the compressor, while the centrifugal force is the outward force that pushes the air away from the center of rotation. These two forces work together to compress the air and increase its pressure.

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• 28.

### (209) A constructional feature of the centrifugal compressor is that the impeller

• A.

Has two matching plates.

• B.

Has a lightweight design.

• C.

Is forged as a single unit.

• D.

Is constructed in rows of blades and stators.

Correct Answer
C. Is forged as a single unit.
Explanation
The correct answer is "is forged as a single unit." This means that the impeller of the centrifugal compressor is manufactured as a single piece, without any separate parts or components. This constructional feature ensures that the impeller is strong, durable, and able to withstand the high speeds and pressures involved in the compression process. By being forged as a single unit, the impeller is also able to maintain its balance and efficiency, leading to better performance of the centrifugal compressor.

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• 29.

### (210) The jet engine compressor that is cheaper to manufacture is the

• A.

Axial-flow type, because of its size.

• B.

Centrifugal type, because of its size.

• C.

Axial-flow type, because of its fewer parts.

• D.

Centrifugal type, because of its fewer parts.

Correct Answer
D. Centrifugal type, because of its fewer parts.
Explanation
The centrifugal type of jet engine compressor is cheaper to manufacture because it has fewer parts compared to the axial-flow type. This means that there are fewer components that need to be produced and assembled, reducing the overall cost of manufacturing.

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• 30.

### (210) Which is a constructional feature of an axial-flow compressor casing?

• A.

Accessory and oil pump mount pads.

• B.

Split along the horizontal centerline.

• C.

Access maintenance ports.

• D.

Solid casting mount lines.

Correct Answer
B. Split along the horizontal centerline.
Explanation
The constructional feature of an axial-flow compressor casing that is being described here is the split along the horizontal centerline. This means that the casing is divided into two halves along its horizontal center, allowing for easy access to the internal components of the compressor for maintenance and repairs. This split design simplifies the disassembly and reassembly process, making it more convenient for technicians to work on the compressor.

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• 31.

### (211) The percentage of combustion efficiency of a gas turbine is usually between

• A.

60 and 70.

• B.

65 and 75.

• C.

75 and 95.

• D.

95 and 100.

Correct Answer
D. 95 and 100.
Explanation
A gas turbine is a type of engine that converts the energy from a flow of gas into mechanical energy. Combustion efficiency refers to the effectiveness of the combustion process in converting fuel into useful energy. A higher percentage indicates a more efficient combustion process, meaning that a larger proportion of the fuel is being converted into usable energy. Therefore, the percentage of combustion efficiency of a gas turbine is usually between 95 and 100, as this range represents a high level of efficiency in converting fuel into energy.

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• 32.

### (211) What is the most probable cause of a flameout of a jet engine flying at 40,000 feet with a constant engine revolutions per minute (rpm) of 50 percent?

• A.

The rpm is too low.

• B.

A decrease in barometric pressure.

• C.

The failure of the breather pressurizing valve.

• D.

Excessive ducting of air from the compressor into the combustion chamber.

Correct Answer
A. The rpm is too low.
Explanation
The most probable cause of a flameout of a jet engine flying at 40,000 feet with a constant engine rpm of 50 percent is that the rpm is too low. When the rpm is too low, it can lead to insufficient fuel flow and inadequate combustion, causing the flame to go out. This can result in a loss of engine power and a flameout.

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• 33.

### (212) The excess airflow that is not burned in the combustion section is used to

• A.

Increase air in the compressor section.

• B.

Mix with and cool the burned gases.

• C.

Decrease the mass of exhaust gases.

• D.

Operate pneumatic accessories.

Correct Answer
B. Mix with and cool the burned gases.
Explanation
The excess airflow that is not burned in the combustion section is used to mix with and cool the burned gases. This is because the combustion process in an engine produces hot gases that need to be cooled down before being expelled as exhaust. The excess airflow is directed towards the burned gases to mix with them and lower their temperature, preventing damage to the engine components and reducing emissions.

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• 34.

### (212) The inner and outer surfaces of an annular-type combustion chamber are formed by

• A.

Interlocking stainless-steel bands.

• B.

The inner and outer diffuser case.

• C.

A forged steel casing.

• D.

Solid sheet metal.

Correct Answer
A. Interlocking stainless-steel bands.
Explanation
The correct answer is interlocking stainless-steel bands. This is because an annular-type combustion chamber is typically made up of multiple stainless-steel bands that interlock with each other to form the inner and outer surfaces of the chamber. This design allows for efficient combustion and containment of the high temperatures and pressures generated during the combustion process.

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• 35.

### (212) Fuel that accumulates after a failed start is

• A.

Drained overboard by a drain system.

• B.

Returned to the fuel control by tubes.

• C.

Burned on the next start attempt.

• D.

Allowed to evaporate.

Correct Answer
A. Drained overboard by a drain system.
Explanation
After a failed start, the fuel that accumulates is drained overboard by a drain system. This means that the excess fuel is removed from the system and disposed of outside the aircraft. This is a common practice to prevent any potential hazards or damage that may occur from the accumulation of fuel.

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• 36.

### (212) The parts on a can-annular combustion section must be removed in a specific order because of the

• A.

Fuel nozzle.

• B.

Transition liner.

• C.

Combustion chamber outer case.

• D.

Combustion chamber crossover tubes.

Correct Answer
D. Combustion chamber crossover tubes.
Explanation
The parts on a can-annular combustion section must be removed in a specific order because of the combustion chamber crossover tubes. These tubes connect the individual combustion chambers in a can-annular configuration, allowing for the flow of gases between them. Removing the crossover tubes first ensures that the combustion chambers are properly isolated and prevents any potential damage or disruption to the fuel nozzle, transition liner, or combustion chamber outer case.

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• 37.

### (212) What is the most common type of fuel nozzle system?

• A.

Pressure-atomizing.

• B.

Fuel-blasting.

• C.

Fuel ejector.

• D.

Fuel tube.

Correct Answer
A. Pressure-atomizing.
Explanation
The most common type of fuel nozzle system is pressure-atomizing. This type of system uses high pressure to atomize the fuel into small particles, allowing for efficient combustion. It is widely used in various applications, including gas turbines, industrial burners, and oil-fired boilers. Pressure-atomizing systems offer better fuel atomization and control compared to other types, resulting in improved combustion efficiency and reduced emissions.

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• 38.

### (213) Three types of turbine and vane assemblies used in jet engines are impulse, reaction, and

• A.

Fir tree.

• B.

Shrouded.

• C.

Unshrouded.

• D.

Reaction-impulse.

Correct Answer
D. Reaction-impulse.
Explanation
The correct answer is reaction-impulse. This answer is correct because the question asks for the three types of turbine and vane assemblies used in jet engines, and the options provided are impulse, reaction, fir tree, shrouded, unshrouded, and reaction-impulse. Out of these options, the correct answer is reaction-impulse as it combines both the impulse and reaction types of turbine and vane assemblies.

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• 39.

### (214) The "fir tree" method of attaching turbine blades (buckets) to the turbine rotor disc is preferred because

• A.

Of the temperature differential between the turbine rotor disc and the blades.

• B.

It aids in preventing horizontal movement of the blades.

• C.

There is less blade tip shake during engine operation.

• D.

It aids in preventing axial movement of the bucket.

Correct Answer
A. Of the temperature differential between the turbine rotor disc and the blades.
Explanation
The "fir tree" method of attaching turbine blades to the turbine rotor disc is preferred because of the temperature differential between the turbine rotor disc and the blades. This method allows for better thermal expansion and contraction of the blades, ensuring a secure and stable attachment even under high temperature conditions.

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• 40.

### (215) In a non-afterburning engine, the exhaust duct connects the turbine outlet and the

• A.

Fan duct.

• B.

Jet nozzle.

• C.

Fuel nozzle.

• D.

Bifurcated duct.

Correct Answer
B. Jet nozzle.
Explanation
In a non-afterburning engine, the exhaust duct connects the turbine outlet and the jet nozzle. The jet nozzle is responsible for accelerating the exhaust gases and creating thrust. This nozzle is specifically designed to increase the velocity of the exhaust gases, allowing for efficient propulsion of the aircraft.

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• 41.

### (215) The purpose of the exhaust duct is to

• A.

Swirl exhaust gas-flow.

• B.

Equalize exhaust gas-flow.

• C.

Straighten exhaust gas-flow.

• D.

Modulate exhaust gas-flow.

Correct Answer
C. Straighten exhaust gas-flow.
Explanation
The purpose of the exhaust duct is to straighten exhaust gas-flow. This means that the exhaust gas, which may be turbulent or uneven, is directed and aligned in a straight path through the duct. This helps to improve the efficiency of the exhaust system by reducing pressure drop and minimizing turbulence. Straightening the exhaust gas-flow also ensures that it exits the system smoothly and without any obstructions, allowing for better performance and reduced emissions.

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• 42.

### (216) What is one common type of variable-area orifice that is used on augmentors?

• A.

Turbine flap.

• B.

Segmented-flap.

• C.

Dual-orifice nozzle.

• D.

Segmented fuel nozzle.

Correct Answer
B. Segmented-flap.
Explanation
A segmented-flap is a common type of variable-area orifice used on augmentors. This type of orifice consists of multiple segments that can be adjusted to vary the size of the orifice opening. By adjusting the position of the segments, the flow area can be increased or decreased, allowing for control over the amount of air or fuel passing through the orifice. This type of variable-area orifice is commonly used in augmentors to regulate the flow of exhaust gases and optimize engine performance.

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• 43.

### (216) The purpose of an augmentor (afterburner) in a jet engine is to

• A.

Augment the maximum thrust capability of the basic engine.

• B.

Increase engine revolutions per minute (rpm).

• C.

Increase exhaust gas temperature (EGT).

• D.

Reduce pressure drop.

Correct Answer
A. Augment the maximum thrust capability of the basic engine.
Explanation
The purpose of an augmentor (afterburner) in a jet engine is to increase the maximum thrust capability of the basic engine. This is achieved by injecting additional fuel into the exhaust stream and igniting it, which increases the temperature and velocity of the exhaust gases. This increased energy output results in a higher thrust output from the engine, allowing for greater acceleration or speed.

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• 44.

### (217) How many different types of loads can be imposed on a jet engine bearing?

• A.

Two.

• B.

Three.

• C.

Four.

• D.

Five.

Correct Answer
B. Three.
Explanation
The correct answer is three because a jet engine bearing can experience three different types of loads: radial loads, axial loads, and moment loads. Radial loads act perpendicular to the axis of rotation, axial loads act parallel to the axis of rotation, and moment loads act to twist or bend the bearing. These three types of loads are important to consider in order to ensure the proper functioning and durability of the jet engine bearing.

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• 45.

### (217) When you handle jet engine bearings, you must change cotton gloves frequently because they

• A.

Attract dirt.

• B.

Wear faster.

• C.

Cause oxidation.

• D.

Get soaked with sweat.

Correct Answer
D. Get soaked with sweat.
Explanation
When handling jet engine bearings, it is important to change cotton gloves frequently because they get soaked with sweat. Sweat can cause the gloves to become wet and damp, which can lead to discomfort and reduced grip. Additionally, the moisture from sweat can potentially damage the bearings or affect their performance. Therefore, changing the gloves frequently helps to maintain a dry and secure grip while handling the bearings.

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• 46.

### (217) Before inspecting new jet engine bearings, you should

• A.

Separate the halves.

• B.

Perform a spin check.

• C.

Apply a preservative coating.

• D.

Remove the preservative coating.

Correct Answer
D. Remove the preservative coating.
Explanation
Before inspecting new jet engine bearings, it is necessary to remove the preservative coating. This is because the preservative coating is applied to protect the bearings during storage and transportation. If the preservative coating is not removed before inspection, it may interfere with the ability to properly assess the condition of the bearings. Therefore, removing the preservative coating is an essential step to ensure accurate inspection and assessment of the new jet engine bearings.

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• 47.

### (218) Next to contamination and improper lubrication, what is the greatest enemy of antifriction bearings?

• A.

Dirt.

• B.

Heat.

• C.

Improper removal.

• D.

Using wrong type of oil.

Correct Answer
C. Improper removal.
Explanation
The greatest enemy of antifriction bearings, next to contamination and improper lubrication, is improper removal. This means that if the bearings are not removed properly, it can cause damage to the bearings and affect their performance. This can lead to premature failure of the bearings and result in costly repairs or replacements. It is important to follow proper procedures and techniques when removing antifriction bearings to ensure their longevity and efficient operation.

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• 48.

### (218) The most commonly used bearing removal tools include

• A.

Drift pipes and hammers.

• B.

Drift pipes and arbor presses.

• C.

Bearing pullers and hammers.

• D.

Arbor presses and bearing pullers.

Correct Answer
D. Arbor presses and bearing pullers.
Explanation
The most commonly used bearing removal tools are arbor presses and bearing pullers. Arbor presses are used to apply force to remove bearings, while bearing pullers are designed specifically for extracting bearings from their housings. These tools are preferred because they provide a safe and efficient way to remove bearings without causing damage to the surrounding components. Hammers and drift pipes are not commonly used for bearing removal as they can cause excessive force and potentially damage the bearings or the equipment.

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• 49.

### (219) Which type of defect appears on bearings as a result of bearing parts striking together?

• A.

Nicks.

• B.

Galling.

• C.

Grooves.

• D.

Scratches.

Correct Answer
A. Nicks.
Explanation
Nicks are a type of defect that appear on bearings as a result of bearing parts striking together. Nicks are small, localized areas of damage or chipping on the surface of the bearing. This can occur when there is excessive load, misalignment, or improper lubrication, causing the parts of the bearing to collide and create small chips or dents. Nicks can lead to increased friction, wear, and potential failure of the bearing if not addressed.

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• 50.

### (219) Which type of defect appears on bearings as a result of small particles of foreign material becoming lodged between the rollers?

• A.

Pits.

• B.

Bands.

• C.

Grooves.

• D.

Brinelling.

Correct Answer
C. Grooves.
Explanation
When small particles of foreign material become lodged between the rollers of bearings, it can cause grooves to appear on the surface. These grooves can lead to increased friction, reduced efficiency, and potential damage to the bearing over time. Pits, bands, and brinelling are not the correct answers because they do not specifically refer to the defect caused by foreign material lodged between the rollers.

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Quiz Review Timeline +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

• Current Version
• Mar 20, 2023
Quiz Edited by
ProProfs Editorial Team
• Sep 29, 2014
Quiz Created by
AustinCope

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