# CDC 2a651s Volume 2 By CDCmaster

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CDCmaster
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Quizzes Created: 4 | Total Attempts: 322
Questions: 88 | Attempts: 100

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• 1.

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

• A.

Bernoulli's principle

• B.

Newton's first law of motion

• C.

Newton's second law of motion

• D.

Newton's third law of motion

B. Newton's first law of motion
Explanation
An aircraft taxiing at a steady speed can be used to demonstrate Newton's first law of motion. This law states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and direction, unless acted upon by an external force. In this case, the aircraft is in motion and continues to move at a constant speed because the thrust from the engines is balanced by the drag and friction forces acting against it.

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• 2.

### 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

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 backward. As a result of this action, there is an equal and opposite reaction, which is the forward thrust generated by the engine. Therefore, the correct answer is forward thrust.

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• 3.

### 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

C. Divergent
Explanation
A divergent duct would decrease the velocity and increase the pressure of a gas as it passes through. In a divergent duct, the cross-sectional area gradually increases along the flow direction. This causes the gas to slow down and the pressure to increase. As the gas flows through the larger area, it experiences a decrease in velocity due to the conservation of mass principle. This decrease in velocity leads to an increase in pressure, according to Bernoulli's principle. Therefore, a divergent duct is the correct answer for this question.

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• 4.

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

• A.

Bernoulli's principle

• B.

Newton's first law of motion

• C.

Newton's second law of motion

• D.

Newton's third law of motion

A. Bernoulli's principle
Explanation
The statement describes how the pressure difference above and below an airfoil creates lift. According to Bernoulli's principle, as the speed of a fluid (in this case, air) increases, its pressure decreases. When air flows over the curved upper surface of an airfoil, it speeds up, resulting in decreased pressure. At the same time, the air flowing underneath the airfoil is slower, causing increased pressure. This pressure difference creates lift, allowing the airfoil (such as an airplane wing) to generate upward force and stay in the air.

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• 5.

### Foot-pounds and inch-pounds are units of measure for

• A.

Work

• B.

Power

• C.

Inertia

• D.

Friction

A. Work
Explanation
Foot-pounds and inch-pounds are units of measure commonly used to quantify work. Work is defined as the amount of energy transferred by a force over a distance. The unit "pound" refers to a unit of force, and when multiplied by a unit of distance (foot or inch), it gives the unit of work. Therefore, foot-pounds and inch-pounds are used to measure the amount of work done in a system.

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• 6.

### What does fuel for an engine represent?

• A.

Available horsepower

• B.

Thrust produced

• C.

Potential energy

• D.

Efficiency ratio

C. Potential energy
Explanation
Fuel for an engine represents potential energy. Potential energy is the stored energy that can be converted into other forms of energy, such as mechanical energy in the case of an engine. Fuel contains chemical potential energy, which is released through combustion to produce energy that can be used to power the engine. Therefore, the fuel in an engine represents the potential energy that can be harnessed to perform work.

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• 7.

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

• A.

Turbine

• B.

Diffuser

• C.

Compressor

• D.

Combustion

C. Compressor
Explanation
The compressor section of a jet engine continually supplies air and maintains pressure. It is responsible for compressing the incoming air before it enters the combustion chamber. This compressed air is then mixed with fuel and ignited to create the necessary thrust for the jet engine. Without the compressor, the air would not be at the required pressure for efficient combustion and propulsion.

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• 8.

### 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

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 raising the temperature of the air increases the kinetic energy of the air molecules, which in turn increases the thrust produced by the engine. By increasing the energy of the compressed air, the jet engine is able to generate more power and propel the aircraft forward.

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• 9.

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

• A.

Turbine

• B.

Diffuser

• C.

Compressor

• D.

Combustion

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, creating a high-temperature and high-pressure environment. The combustion process releases energy in the form of hot gases, which then flow through the turbine section to generate thrust. The combustion section is crucial for the operation of a jet engine as it provides the necessary power to propel the aircraft forward.

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• 10.

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

• A.

10500

• B.

15000

• C.

18500

• D.

40000

C. 18500
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.

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

• A.

Energy

• B.

Momentum

• C.

Thermal efficiency

• D.

Propulsive efficiency

C. Thermal efficiency
Explanation
The efficiency of a jet engine is often referred to as thermal efficiency because it measures how effectively the engine converts the heat energy from burning fuel into useful mechanical work. This is an important parameter to evaluate the performance of a jet engine, as a higher thermal efficiency indicates that more of the heat energy is being converted into useful work, resulting in better fuel economy and overall performance.

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• 12.

### The product of thermal efficiency and propulsive efficiency is

• A.

Mechanical efficiency

• B.

Overall efficiency

• C.

Power efficiency

• D.

Thrust efficiency

B. Overall efficiency
Explanation
The product of thermal efficiency and propulsive efficiency is referred to as overall efficiency. This is because thermal efficiency measures the ratio of useful work output to the heat input, while propulsive efficiency measures the ratio of useful work output to the power input. Multiplying these two efficiencies together gives the overall efficiency, which represents the overall effectiveness of a system in converting energy inputs into useful work outputs.

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• 13.

### To measure barometric pressure, you would use a

• A.

Potentiometer

• B.

Psychrometer

• C.

Pyrometer

• D.

Barometer

D. Barometer
Explanation
A barometer is used to measure barometric pressure, which is the pressure exerted by the atmosphere. It is specifically designed for this purpose and provides accurate readings of atmospheric pressure. A potentiometer is an electrical component used to measure and control voltage, so it is not suitable for measuring barometric pressure. A psychrometer is used to measure relative humidity, not barometric pressure. A pyrometer is used to measure high temperatures, such as in industrial processes, and is not designed for measuring barometric pressure. Therefore, the correct answer is barometer.

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• 14.

### 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

B. More moisture, less dense
Explanation
When there is more moisture in the air, it displaces some of the dry air molecules, leading to a decrease in the overall density of the air. This is because water molecules are lighter than the average molecular weight of dry air, which is mostly composed of nitrogen and oxygen. Therefore, the presence of more moisture in the air causes it to become less dense.

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• 15.

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

• A.

Remains the same

• B.

Fluctuates

• C.

Decreases

• D.

Increases

D. Increases
Explanation
A diffuser is designed to slow down the flow of a fluid, in this case, air. As the air enters the diffuser, its velocity decreases, causing an increase in pressure. This is due to the conservation of mass and energy principles. Therefore, the correct answer is that the air pressure increases in a diffuser.

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• 16.

### 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

A. Compression
Explanation
The air temperature of a jet engine gradually rises across the compressor to the diffuser outlet as a result of compression. As the air passes through the compressor, it is compressed, which leads to an increase in temperature. This is because the compression process causes the air molecules to collide more frequently and with greater force, resulting in an increase in their kinetic energy and therefore temperature. Therefore, compression is the main factor responsible for the gradual temperature rise in the jet engine.

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• 17.

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

• A.

Tailpipe

• B.

Exhaust cone

• C.

Turbine section

• D.

Combustion section

D. Combustion section
Explanation
The highest point of temperature in an engine is reached in the combustion section. This is where the fuel and air mixture is ignited and burned, resulting in a rapid increase in temperature and pressure. The combustion section is designed to withstand these extreme temperatures and pressures, and it is where the energy is generated to power the engine.

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• 18.

### Which engine component meters fuel for combustion?

• A.

Pressure and drain (P&D) valve

• B.

Fuel control

• C.

Fuel nozzle

• D.

Fuel pump

B. Fuel control
Explanation
The fuel control component is responsible for metering fuel for combustion in an engine. It regulates the amount of fuel that is delivered to the engine based on various factors such as engine speed, load, and temperature. By controlling the fuel flow, the fuel control ensures that the engine receives the correct amount of fuel for efficient and effective combustion. This helps to optimize engine performance and fuel efficiency.

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• 19.

### 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

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. As the turbine wheel rotates, it transfers the energy back to the compressor, which then uses it to compress the incoming air. This process is essential for the functioning of the turbine engine, as it helps maintain a continuous flow of air and fuel for combustion.

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• 20.

### 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

D. Greater velocity exiting than entering
Explanation
The correct answer is "Greater velocity exiting than entering." In a jet engine, air and gases are compressed and heated before being expelled at a high velocity through the exhaust nozzle. This high velocity is necessary to generate thrust and propel the aircraft forward. The exit velocity is greater than the entering velocity to create a net force in the opposite direction, according to Newton's third law of motion.

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• 21.

### 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)

A. Ejector nozzle
Explanation
The ejector nozzle is the correct answer because it is the part of the jet engine where the stream of air reaches its highest velocity. This nozzle is responsible for accelerating the exhaust gases from the combustion process, creating a high-speed jet of air that propels the aircraft forward.

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• 22.

### 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

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 are directed in the same direction as the rotor shaft, creating a linear flow. This flow is important for the efficient operation of the combustion chamber and the overall functioning of the system.

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• 23.

### Gases enter the jet-engine's first-stage turbine wheel blades from the

• A.

• B.

Combustion chamber

• C.

Turbine stator

• D.

Flameholder

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. It is responsible for directing the flow of gases towards the turbine blades, which then convert the gas energy into mechanical energy to drive the engine.

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• 24.

### 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)

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 helps to direct the flow of exhaust gases onto the turbine blades, ensuring efficient energy transfer from the high-pressure gases to the turbine. It also helps to maintain a uniform flow of gases and prevent turbulence, which can affect the performance of the turbine wheels.

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• 25.

### 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

A. An exhaust-gas-driven turbine wheel to drive its compressor
Explanation
The correct answer is that a jet engine uses 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, and this power is used to drive the compressor, which in turn compresses the incoming air before it enters the combustion chamber. This design allows the engine to generate the necessary thrust for propulsion.

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• 26.

### A turbo-supercharger is essentially a

• A.

Jet engine

• B.

High-capacity air pump

• C.

Temperature reduction device

• D.

High-volume air direction device

B. High-capacity air pump
Explanation
A turbo-supercharger is a device that increases the amount of air flowing into an engine, thereby increasing its power output. It achieves this by using a turbine to harness the exhaust gases from the engine and drive a compressor, which compresses the incoming air before it enters the engine. This compressed air allows for more fuel to be burned, resulting in increased power. Therefore, a turbo-supercharger can be described as a high-capacity air pump, as it significantly boosts the amount of air supplied to the engine.

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• 27.

### 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.

A. Rotational and centrifugal
Explanation
The correct answer is rotational and centrifugal. When air is drawn into the guide vanes of a centrifugal compressor, it experiences two forces. The rotational force is caused by the spinning motion of the compressor impeller, which imparts a swirling motion to the air. The centrifugal force is a result of the air being pushed outward due to the curved shape of the impeller blades. These two forces work together to compress the air and increase its pressure before it is discharged from the compressor.

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• 28.

### 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

C. Is forged as a single unit
Explanation
The correct answer is "is forged as a single unit." In a centrifugal compressor, the impeller is forged as a single unit, meaning it is manufactured as one solid piece. This design ensures the impeller is strong and durable, as there are no joints or seams that could weaken over time. By being forged as a single unit, the impeller can effectively handle the high-speed rotation required for the compressor to function efficiently.

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• 29.

### 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 fewer parts

D. Centrifugal type, because of 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 is less complexity in the manufacturing process, resulting in lower production costs.

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• 30.

### 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

B. Split along the horizontal centerline
Explanation
The correct answer is "Split along the horizontal centerline." This constructional feature refers to the casing of an axial-flow compressor being divided into two halves along the horizontal centerline. This split allows for easier access to the compressor blades and other internal components for maintenance and repair purposes. It also facilitates the installation and removal of the compressor rotor.

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• 31.

### 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

D. 95 and 100
Explanation
The percentage of combustion efficiency of a gas turbine is usually between 95 and 100 because gas turbines are designed to be highly efficient in converting the energy from the combustion process into mechanical energy. A combustion efficiency of 95 to 100 percent indicates that almost all of the fuel is being fully burned and converted into useful work, resulting in minimal waste and maximum energy output. This high level of efficiency is desirable in order to maximize the performance and cost-effectiveness of gas turbine systems.

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• 32.

### What is the most probable cause of a flameout of a jet engine flying at 40,00 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

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 low, it can lead to insufficient fuel-air mixture in the combustion chamber, resulting in a flameout. This can happen especially at higher altitudes where the air is thinner and requires a higher RPM to maintain proper combustion.

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• 33.

### 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

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 process helps to lower the temperature of the exhaust gases, preventing damage to the engine components and reducing emissions. By mixing the excess airflow with the burned gases, the overall temperature is reduced, improving the efficiency and performance of the engine.

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• 34.

### 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

A. Interlocking stainless-steel bands
Explanation
The correct answer is interlocking stainless-steel bands. This means that the inner and outer surfaces of an annular-type combustion chamber are formed by multiple stainless-steel bands that interlock with each other. These bands provide the necessary strength and durability to withstand the high temperatures and pressures generated during combustion. Using interlocking bands also allows for easy assembly and disassembly of the combustion chamber for maintenance and repair purposes.

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• 35.

### 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

A. Drained overboard by a drain system
Explanation
After a failed start, the fuel that accumulates is drained overboard by a drain system. This is necessary to prevent any potential hazards or damage that could occur if the fuel were to remain in the system. By draining the fuel overboard, it ensures that the fuel is safely removed from the system and does not interfere with future start attempts.

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• 36.

### The parts on a can-annular combustion chamber 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

D. Combustion chamber crossover tubes
Explanation
The parts on a can-annular combustion chamber section must be removed in a specific order because of the combustion chamber crossover tubes. These tubes connect the different combustion chambers in the can-annular design, allowing for the flow of gases and combustion products. Removing the crossover tubes before other components ensures that the flow of gases is properly managed and that the combustion chamber can be disassembled without causing damage or disruption to the system.

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• 37.

### What is the most common type of fuel nozzle system

• A.

Pressure-atomizing

• B.

Fuel-blasting

• C.

Fuel ejector

• D.

Fuel tube

A. Pressure-atomizing
Explanation
The most common type of fuel nozzle system is the pressure-atomizing system. This system uses high pressure to atomize the fuel into fine particles, allowing for efficient combustion. It is widely used in various industries, including aviation and power generation, due to its ability to provide a fine spray of fuel for optimal combustion efficiency.

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• 38.

### 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

D. Reaction-impulse
Explanation
The correct answer is "reaction-impulse". This answer refers to a combination of both reaction and impulse turbine and vane assemblies used in jet engines. A reaction turbine uses the principle of Newton's third law of motion, where the change in momentum of the fluid produces a force on the turbine blades. An impulse turbine, on the other hand, uses the principle of Newton's second law of motion, where the change in momentum of the fluid produces a change in velocity of the fluid, resulting in a force on the turbine blades. The reaction-impulse turbine and vane assembly combines both of these principles to optimize the efficiency and performance of the jet engine.

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• 39.

### 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

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 helps to accommodate the expansion and contraction of the blades due to the temperature difference, ensuring a secure and stable attachment.

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• 40.

### 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

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 the thrust necessary for propulsion. It is designed to maximize the velocity of the exhaust gases and increase the efficiency of the engine. The fan duct, fuel nozzle, and bifurcated duct are not directly involved in the exhaust process and do not play a role in accelerating the gases.

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• 41.

### 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

C. Straighten exhaust gas flow
Explanation
The purpose of the exhaust duct is to straighten the exhaust gas flow. This means that the duct is designed in a way that reduces turbulence and ensures a smooth and efficient flow of exhaust gases out of the system. By straightening the flow, the exhaust gases can exit the system more easily, improving overall performance and reducing any potential backpressure.

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• 42.

### 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

B. Segmented-flap
Explanation
A segmented-flap is a common type of variable-area orifice used on augmentors. This type of orifice has multiple segments that can be adjusted to control the flow of air or fuel. By adjusting the position of the segments, the area of the orifice can be changed, allowing for precise control of the flow rate. This type of orifice is often used in turbine engines to regulate the amount of air or fuel entering the augmentor, optimizing performance and efficiency.

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• 43.

### 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

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. The augmentor achieves this 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, allowing the jet engine to produce more power and achieve greater performance.

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• 44.

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

• A.

Two

• B.

Three

• C.

Four

• D.

Five

B. Three
Explanation
There are three different types of loads that can be imposed on a jet engine bearing.

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• 45.

### 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

D. Get soaked with sweat
Explanation
When handling jet engine bearings, it is necessary to change cotton gloves frequently because they get soaked with sweat. This is important because sweat can cause the gloves to become wet and damp, which can compromise their effectiveness in providing a protective barrier. Additionally, wet gloves can also lead to discomfort and reduced dexterity, making it necessary to change them regularly to maintain optimal performance and safety.

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• 46.

### Before inspecting new jet engine bearings, you should

• A.

Separate the halves

• B.

Perform a spin check

• C.

Apply a preservative

• D.

Remove the preservative

D. Remove the preservative
Explanation
Before inspecting new jet engine bearings, it is necessary to remove the preservative. This is important because the preservative is applied to protect the bearings during storage and transportation. However, it can interfere with the inspection process and potentially affect the performance of the bearings if not removed. Therefore, removing the preservative ensures that the bearings can be properly inspected for any potential issues or defects before they are installed in the jet engine.

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• 47.

### 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

C. Improper removal
Explanation
Improper removal refers to the incorrect or careless removal of the antifriction bearings from their designated positions. This can lead to damage or misalignment of the bearings, causing them to function improperly or fail altogether. Improper removal can include using excessive force, using incorrect tools, or not following the proper procedure for removal. Therefore, improper removal can be considered as a significant enemy of antifriction bearings, as it can greatly reduce their lifespan and efficiency.

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• 48.

### 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

D. Arbor presses and bearing pullers
Explanation
Arbor presses and bearing pullers are commonly used tools for removing bearings. Arbor presses provide a controlled and precise force to push the bearing out of its housing, while bearing pullers are designed to grip onto the bearing and pull it out. These tools are preferred over hammers and drift pipes as they minimize the risk of damaging the bearing or the surrounding components during removal.

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• 49.

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

• A.

Nicks

• B.

Galling

• C.

Grooves

• D.

Scratches

A. Nicks
Explanation
Nicks are a type of defect that appears on bearings as a result of bearing parts striking together. When two parts of a bearing come into contact with each other, it can cause small chips or nicks to form on the surface. These nicks can lead to further damage and affect the overall performance and lifespan of the bearing. Galling, grooves, and scratches are also types of defects that can occur on bearings, but in this case, the correct answer is nicks.

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• 50.

### 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

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 are a type of defect that can impair the smooth operation of the bearing. They can lead to increased friction, wear, and potential failure of the bearing over time. Therefore, the correct answer is "Grooves".

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