2A551 Practice Test Volume 3

Energy is defined as the ability to do work. It is a measure of the capacity or ability of a system to perform work or produce a change. In physics, energy can exist in different forms such as kinetic energy, potential energy, thermal energy, etc. In this case, the correct answer is energy because it aligns with the definition given in the question.

The valve that permits jet engine oil flow in only one direction is the check valve. This valve allows oil to flow in one direction while preventing it from flowing back in the opposite direction. It ensures that oil flows properly through the engine, providing lubrication and cooling, without any backflow or leakage.

Using mouth suction to take jet engine oil samples can be extremely dangerous because the oil may contain harmful chemicals or toxins that can cause paralysis or even death if ingested.

Dirt and sand are the most common contaminants found in lubrication systems. These particles can enter the system through various means such as air intake, improper handling, or wear and tear of components. The presence of dirt and sand in the lubrication system can cause abrasive wear, clog filters, reduce lubricant effectiveness, and ultimately lead to equipment failure if not properly addressed. Regular maintenance and filtration are crucial to prevent or remove these contaminants from the lubrication system.

Electrohydromechanical fuel control uses various components like thermocouples, relays, amplifiers, and solenoids to regulate the engine. These components work together to monitor and adjust the fuel flow based on the engine's requirements. The use of electricity allows for precise control and quick response, while the hydromechanical aspect ensures the proper delivery of fuel. This type of fuel control system combines the advantages of both electrical and hydraulic systems, making it an effective and efficient method for controlling the engine's fuel supply.

In a jet engine, the gases and air flow through at a high velocity to generate thrust. This is achieved by compressing the air and gases and then igniting them with fuel. As the air and gases pass through the engine, they experience an increase in pressure and temperature. According to the principle of conservation of momentum, the increase in pressure causes the gases to accelerate and exit the engine at a greater velocity than they entered. This high velocity of the exiting gases creates a force in the opposite direction, propelling the aircraft forward. Therefore, the correct answer is that the velocity exiting the jet engine is greater than the velocity entering.

The purpose of the exhaust duct is to straighten the exhaust gas flow. This means that it is designed to remove any turbulence or irregularities in the flow of the exhaust gases, ensuring that they flow smoothly and evenly through the duct. Straightening the exhaust gas flow is important for efficient and effective ventilation, as it helps to prevent any blockages or restrictions that could impede the flow of gases and potentially cause damage or inefficiency in the system.

Aircraft engine indicating instruments need to be light in weight to avoid adding unnecessary weight to the aircraft, which can affect its performance. They also need to be small in size to fit into the limited space available in the cockpit. Additionally, they need to be easy to read for the pilots to quickly and accurately interpret the information displayed.

The term "combustion range" refers to the operating temperature zone of a jet engine. This is the range of temperatures at which the engine is designed to operate efficiently and effectively. It is important for the engine to maintain a certain temperature range to ensure proper combustion of fuel and optimal performance. The other options, such as steady state zone, pressure ratio zone, and compressor stall zone, do not accurately describe the concept of combustion range.

The most chemically correct ratio for burning fuel in a combustion chamber is 15:1. This means that for every 15 units of air, there should be 1 unit of fuel. This ratio ensures that there is enough oxygen present in the combustion chamber to completely burn the fuel, resulting in efficient and clean combustion. A higher ratio of air to fuel helps prevent the formation of harmful byproducts such as carbon monoxide and unburned hydrocarbons.

A differential pressure indicator is actuated when a fuel filter is clogged. This means that there is a pressure difference between the inlet and outlet of the filter, indicating that the filter is restricting the flow of fuel. This can be observed during a visual inspection, without the need to disassemble the filter.

The purpose of an oil-temperature control valve used with air/oil coolers is to direct oil around or through the cooler. This valve helps regulate the temperature of the oil by controlling its flow through the cooler. By directing the oil around or through the cooler, the valve ensures that the oil is properly cooled before returning to the engine or other components. This helps maintain optimal operating temperatures and prevents overheating of the oil, which can lead to engine damage.

An aircraft taxiing at a constant rate of speed is an example of Newton's First Law of Motion, also known as the law of inertia. 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 in the same direction, unless acted upon by an external force. In this case, the aircraft is already in motion and continues to move at a constant speed without any external force acting on it, demonstrating Newton's First Law of Motion.

The average percentage of a jet engine's energy required to maintain engine operation is 60. This means that out of the total energy produced by the engine, 60% is used to keep the engine running smoothly. This includes powering essential components such as the fuel system, lubrication system, and electrical systems necessary for engine operation. The remaining percentage of energy is then available to generate thrust and propel the aircraft forward.

In a jet engine, the diffuser is responsible for decreasing the velocity of the air. The diffuser is located at the entrance of the engine and its purpose is to slow down the incoming air by increasing its pressure. This is achieved by gradually expanding the cross-sectional area of the diffuser, which causes the air to decelerate. This slower air is then passed on to the compressor, where it is further pressurized before entering the combustion chamber.

A jet engine derives its name from the fact that it uses an exhaust-gas-driven turbine wheel to drive its compressor. This means that the engine uses the force of the exhaust gases to spin a turbine wheel, which in turn powers the compressor. The compressor then compresses incoming air, which is mixed with fuel and ignited to produce thrust. This design allows the engine to generate the power needed for flight.

The three major sections of all jet engines are the compressor, combustion, and turbine. The compressor takes in air and compresses it, the combustion section mixes the compressed air with fuel and ignites it, and the turbine extracts energy from the hot gases to power the compressor and other engine accessories. The exhaust is the final section where the gases exit the engine. Therefore, the correct answer is turbine.

A gasket is the correct answer because it is specifically designed to create a static seal between two stationary parts in the oil system. Gaskets are typically made of materials such as rubber, cork, or metal, and they are placed between two surfaces to prevent leakage of fluids or gases. By compressing the gasket between the two parts, a tight seal is created, ensuring that the oil system remains sealed and free from leaks.

Raising the air temperature in a jet engine increases the energy because it allows for better combustion of fuel. When the air temperature is increased, the fuel burns more efficiently, resulting in a higher energy output. This increased energy output leads to greater thrust and overall performance of the jet engine.

Inertia is the property of matter that describes its resistance to change in motion. It is the tendency of an object to maintain its current state of motion, whether it is at rest or in motion. This resistance to change in motion is a fundamental characteristic of matter and is not directly related to energy, friction, or potential.

The percentage of combustion efficiency of a gas turbine is usually between 95 and 100. This means that the gas turbine is able to convert a high percentage of the fuel's energy into mechanical work. A combustion efficiency in this range indicates that the turbine is operating at a highly efficient level, minimizing energy losses and maximizing power output. Higher combustion efficiency translates to lower fuel consumption and reduced emissions, making it an ideal range for gas turbine performance.

The most common type of fuel nozzle system is the pressure-atomizing. This type of system uses pressure to atomize the fuel, breaking it up into small particles for efficient combustion. It is widely used in various applications, including industrial burners, gas turbines, and oil-fired boilers. The pressure-atomizing system offers better control over fuel flow and combustion efficiency compared to other types of fuel nozzle systems.

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 stainless steel bands that interlock with each other. This construction method provides strength and stability to the combustion chamber, allowing it to withstand high temperatures and pressure during the combustion process. The interlocking design also helps to prevent any leakage or failure of the combustion chamber, ensuring the safe and efficient operation of the engine.

Pressure pulsations can rapidly reduce the efficiency of a centrifugal jet engine compressor. This is because pressure pulsations can disrupt the smooth flow of air through the compressor, leading to turbulence and inefficiencies. The pulsations can cause fluctuations in the pressure and disrupt the compression process, resulting in reduced efficiency. In contrast, the other options, such as resultant velocity, tangential velocity, and air mass leaving the impeller at greater velocities, may have an impact on the compressor's performance, but they are not specifically mentioned as conditions that rapidly reduce its efficiency.

The correct answer is "four bladed, reversible pitch propeller; 13.5 feet in diameter" because it matches the description given in the question. It states that the Hamilton Standard 54H60-91 propeller has four blades, a reversible pitch, and a diameter of 13.5 feet.

The centrifugal engine is cheaper to manufacture because it has fewer parts compared to the axial flow engine. This means that there are fewer components that need to be manufactured, assembled, and maintained, resulting in lower production costs.

Swirl type fuel nozzles are designed to create a swirling motion in the fuel-air mixture, resulting in better fuel atomization and mixing. This leads to a more efficient combustion process and a higher flame speed. Therefore, the correct answer is high.

Electrically heated elements are a method of deicing a propeller. This involves using elements that are heated by electricity to melt any ice or snow that has accumulated on the propeller blades. The heat generated by these elements helps to prevent ice from forming or to remove any ice that has already formed, ensuring that the propeller can function properly and safely. This method is commonly used in aircraft deicing systems to ensure that propellers remain ice-free during flight.

The correct answer is impulse, reaction, and reaction-impulse. This answer accurately identifies the three design types of turbines used in jet engines. Impulse turbines convert the kinetic energy of the gas flow into mechanical energy through a series of fixed and moving blades. Reaction turbines, on the other hand, convert both the kinetic energy and the pressure energy of the gas flow into mechanical energy. Reaction-impulse turbines combine both impulse and reaction principles to achieve efficient energy conversion.

The turbine bucket on some jet engines is secured in place by lock strips. Lock strips are metal strips that are tightly wound around the bucket to prevent it from moving or coming loose during operation. This method of securing the bucket is preferred as it provides a strong and reliable hold, ensuring the safety and efficiency of the engine. Screws, cables, and lockwire are not commonly used to secure turbine buckets in jet engines.

The flameholder is the component that creates local turbulence and reduces gas velocity in a combustion system. By disrupting the flow of the fuel-air mixture, the flameholder promotes better mixing and enhances combustion efficiency. It also helps to stabilize the flame by preventing flashback and ensuring that the flame remains in the desired location. Therefore, the flameholder is responsible for creating local turbulence and reducing gas velocity in the system.

The oil cooler that operates on the same principle as an automotive radiator is the air/oil cooler. This type of cooler uses air to cool down the oil, just like a radiator uses air to cool down the coolant in a car's engine. The air/oil cooler typically consists of fins or tubes through which the oil flows, and air is blown over these fins or tubes to dissipate the heat from the oil. This helps to maintain the oil at an optimal temperature and prevent it from overheating, ensuring smooth operation of the system.

The correct answer is the pressurizing and dump (P&D) Valve. The pressurizing and dump valve is responsible for controlling the pressurization of the engine fuel system. It regulates the fuel pressure by either increasing or decreasing it as necessary. This valve ensures that the fuel system operates at the correct pressure levels for optimal engine performance.

The advantage of the high energy capacitor type jet engine ignition system is that it makes starting possible when the igniter plugs are fouled. This means that even if the igniter plugs become dirty or clogged, the high energy capacitor type ignition system can still ignite the fuel and start the engine. This is beneficial because it ensures that the engine can be started even in less than ideal conditions, increasing the reliability and efficiency of the jet engine.

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A segmented flap is a common type of variable-area orifice used on augmenters. This type of flap is divided into segments, allowing for precise control of the airflow. By adjusting the position of the segments, the area of the orifice can be modified, regulating the flow of air. This design offers flexibility and accuracy in controlling the airflow, making it suitable for use in augmenters.

The correct answer is increased equipment availability. This means that by participating in the Joint Oil Analysis Program (JOAP), organizations are able to identify potential issues with their equipment early on through oil analysis. This allows them to take proactive measures to prevent breakdowns and keep their equipment running smoothly, ultimately increasing its availability for use.

The fuel control in a jet engine is responsible for metering the fuel for combustion. It regulates the flow of fuel based on various factors such as engine speed, altitude, and temperature. The fuel control ensures that the correct amount of fuel is supplied to the engine for efficient combustion and optimal performance. It plays a crucial role in maintaining the engine's power output and fuel efficiency.

In a jet engine, a nozzle diaphragm is placed directly in front of each turbine wheel when two or more turbine wheels are used. The nozzle diaphragm helps to direct and control the flow of exhaust gases from the combustion chamber towards the turbine blades, ensuring efficient operation of the turbine and ultimately the engine.

A simple direct current (DC) ignition system consists of a vibrator, igniter plugs, and a transformer. The vibrator is responsible for converting the battery's DC current into an oscillating current. The AC-DC converter then converts this oscillating current into a high voltage DC current. This high voltage current is then passed through the transformer, which steps up the voltage even further. Finally, the high voltage current is delivered to the igniter plugs, which create a spark to ignite the fuel-air mixture in the engine.

The EGT indicators are used to measure the temperature of the engine's exhaust gases. This temperature is typically measured in degrees Celsius, which is the correct answer. British Thermal Units (BTUs) per hour is a unit of energy, pounds per square inch (PSI) is a unit of pressure, and degrees Fahrenheit is another unit of temperature, but the EGT indicators specifically measure the temperature in degrees Celsius.

The divergent design of a jet engine diffuser increases pressure. A diffuser is a component that slows down and expands the high-speed airflow coming out of the engine. The divergent shape of the diffuser allows the airflow to expand gradually, which leads to a decrease in velocity and an increase in pressure. This design helps to efficiently convert the kinetic energy of the airflow into pressure energy, which is essential for the proper functioning of the engine.

The air turbine (impingement) starter used on jet engines has the advantages of less weight and fewer moving parts than other starters. This means that it is lighter and simpler, which can be beneficial for aircraft applications where weight and complexity are important factors.

The correct answer is ejector nozzle. In a jet engine, the velocity of the stream of air reaches its highest point at the ejector nozzle. This is because the ejector nozzle accelerates the exhaust gases to create thrust, propelling the aircraft forward. The high velocity of the air at the ejector nozzle is crucial for generating the necessary thrust for flight.

The most common type of oil pump used is the gear pump. This type of pump consists of two interlocking gears that create a pumping action to move the oil. As the gears rotate, oil is trapped in the spaces between the gear teeth and is carried around the pump housing. The gears then mesh together, forcing the oil out through the outlet. Gear pumps are known for their simplicity, reliability, and ability to handle high pressures, making them a popular choice for oil pumping applications.

A transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction. In the case of a jet engine AC ignition system, the transformer is responsible for increasing the voltage from the power source to 20,000 volts, which is then delivered to the igniter plugs. This high voltage is necessary for the ignition process in the jet engine. Therefore, the transformer is the correct unit for developing and delivering the required voltage for the igniter plugs in the AC ignition system of a jet engine.

Rotogear is not a type of oil pump because it is not a recognized classification or design of oil pump. The other options listed - Gear, Gerotor, and Sliding Vane - are all well-known types of oil pumps used in various applications. However, Rotogear is not a commonly used or recognized term in the context of oil pumps.

Foot-pounds and inch-pounds are units of measure for power. Power is the rate at which work is done or energy is transferred. Foot-pounds and inch-pounds are both units that combine a force (pounds) with a distance (foot or inch) to measure the amount of work or power being exerted. Therefore, the correct answer is power.