2A651 Edition2 Volume 5

After an occurrence of a specific or unusual condition, maintenance personnel conduct a special inspection. This inspection is carried out to assess and identify any potential damage or issues caused by the condition. It allows maintenance personnel to determine the necessary repairs or replacements needed to ensure the continued safe and efficient operation of the equipment or system.

The correct answer is "individuals assigned". This means that the responsibility for the proper preventive maintenance of a test cell facility rests with the individuals who have been assigned to that task. It implies that there is no specific unit or squadron designated for this responsibility, but rather it is the duty of the individuals who have been assigned to the test cell facility.

The correct answer is to eliminate items that could possibly cause foreign object damage (FOD). This is important because loose nuts, bolts, lock wire, tools, or any other material left in the engine or quick engine change (QEC) kit could potentially get sucked into the engine during the test run, causing damage to the engine and potentially leading to a catastrophic failure. By checking and removing any loose items before the test, the risk of FOD is minimized, ensuring the safety and proper functioning of the engine.

The engine fuel-flow indicating system of most jet powered aircraft contains a fuel-flow transmitter and a fuel-flow indicator. This system is responsible for measuring and displaying the rate at which fuel is flowing into the engine. The fuel-flow transmitter measures the flow of fuel and sends this information to the fuel-flow indicator, which then displays the data to the pilot. This allows the pilot to monitor the fuel consumption and make any necessary adjustments during the flight.

An understanding of the operating principles of engine instruments is important in order to interpret the readings provided by these instruments. By understanding the meanings of the instrument readings, one can determine the performance and condition of the engine. This knowledge is necessary to make informed decisions about whether an engine should be removed from an aircraft or sent to the test cell for further examination and maintenance.

A typical jet engine exhaust gas temperature (EGT) indicating system contains a resistor. The resistor is used to measure the temperature of the exhaust gas. The thermocouples and leads are used to sense the temperature and transmit the signal to the indicator. The indicator then displays the temperature reading. The turbine inlet and control valve are not directly related to the EGT indicating system.

Pressing only the TEST switch during the operational check of the fire warning system is the correct answer. This is because the TEST switch is specifically designed to initiate a test of the system, allowing the operator to verify its functionality. Pressing both the TEST and NORMAL switches or only the TEST WARNING ON switch would not provide a comprehensive test of the system. Pressing both the TEST ON and TEST OFF switches is not a valid option as there is no mention of these switches in the question.

Rapid throttle movement can cause a compressor stall during emergency system operation. This is because sudden and excessive changes in throttle position can disrupt the airflow through the engine, leading to a loss of compressor efficiency and potentially causing the compressor to stall.

When making general entries on the test cell engine log sheet, it is important to verify the engine model and serial number on the engine data plate. This ensures that the correct information is recorded and avoids any mistakes or discrepancies in the log sheet. Checking past records may provide some reference, but it is crucial to verify the numbers on the engine data plate to ensure accuracy. Entering these numbers only after the test is complete may lead to errors if the wrong numbers are recorded during the test.

Most engine monitoring gauges and instruments require a transmitter and indicator because these devices work together to measure and display various parameters of the engine. The transmitter converts the physical measurements into electrical signals, which are then transmitted to the indicator. The indicator receives these signals and displays the readings on the gauge or instrument panel. Therefore, both the transmitter and indicator are necessary components for accurate engine monitoring.

To become an expert troubleshooter, it is important to understand the function of each unit within each system. This means having a comprehensive knowledge and understanding of how each component within a system works and interacts with other components. This knowledge allows troubleshooters to accurately diagnose and fix issues that may arise within a system. While being a 7-level, having at least 5 years of experience, and attending college courses in troubleshooting techniques may contribute to becoming an expert troubleshooter, understanding the function of each unit within each system is the most essential factor in achieving expertise.

Aircraft instruments need to be small in size in order to be considered effective tools for aviators. This is because space is limited in an aircraft cockpit, and there are numerous instruments that need to be installed. Therefore, having small instruments allows for efficient use of space and ensures that all necessary instruments can be accommodated without cluttering the cockpit. Additionally, small instruments are also easier to read and manipulate, which is crucial for pilots who need to quickly and accurately interpret the information provided by the instruments while flying.

To determine the specific engine's correct type and grade of oil used, one should refer to the applicable engine publications. These publications contain the necessary information regarding the engine's oil requirements and specifications. It is important to consult these publications to ensure that the correct oil is used during the test cell run, as using the wrong type or grade of oil could potentially damage the engine. The base engine manager's office may have some information, but the most accurate and up-to-date information can be found in the applicable engine publications. The test cell oil formulas and periodic checklist for the engine may not provide the specific information required for determining the correct type and grade of oil.

Alumel and chromel are used in the thermocouples of the exhaust gas temperature (EGT) indicating system. These metals are commonly used in thermocouples due to their high temperature resistance and good electrical conductivity. Alumel is an alloy of nickel, manganese, aluminum, and silicon, while chromel is an alloy of nickel and chromium. The combination of these two metals allows for accurate temperature measurement in high-temperature environments such as exhaust systems.

The filter selector switch on the vibration analyzer allows the user to choose the appropriate filter for analyzing the vibration data. Different filters are used to isolate specific frequencies or ranges of frequencies, allowing for a more accurate assessment of the vibration characteristics. By selecting the necessary filter, the user can focus on the specific vibration components of interest and eliminate any unwanted noise or interference.

To begin troubleshooting after reviewing the aircraft/engine forms, one should observe gauge indications. This is because gauge indications provide valuable information about the performance and condition of various systems in the aircraft/engine. By observing the gauge indications, one can identify any abnormal readings or discrepancies that may indicate a problem or malfunction. This is a logical starting point as it allows for a systematic approach to identifying and resolving any issues.

The tachometer indicating system consists of two primary units: the tachometer generator and the indicator. The tachometer generator is responsible for generating electrical signals based on the rotational speed of the engine, while the indicator is the device that displays the speed on the tachometer. Therefore, the correct answer is "indicator".

The correct answer is to examine the unit that requires the least amount of time to replace. This is because when encountering engine trouble where more than one unit is at fault, it is more efficient to start by examining and potentially replacing the unit that can be replaced quickly. This allows for a quicker diagnosis and resolution of the problem, and if it does not fix the issue, then further examination and replacement of other units can be done.

Service inspections are conducted on the test cell on a daily basis. This means that the inspections occur every day, ensuring that the test cell is regularly checked for any issues or maintenance needs. Conducting daily service inspections helps to ensure the proper functioning and safety of the test cell, allowing any problems to be identified and addressed promptly.

A piezoelectric accelerometer is made up of certain ceramic compounds and natural crystals. These materials have the property of generating an electric charge when subjected to mechanical stress or vibration. This electric charge is then converted into an electrical signal that can be measured and analyzed to determine the level and frequency of the vibration. Therefore, a piezoelectric accelerometer is the correct type of vibration transducer that is made up of certain ceramic compounds and natural crystals.

During engine coast down, a final check for leaks is accomplished in a test cell leak check. This step involves observing the engine as it slows down after being shut off, and checking for any signs of leaks or abnormal fluid levels. This is an important step to ensure that there are no leaks in the test cell, which could affect the accuracy of the test results and potentially cause damage to the equipment.

Foreign object damage (FOD) refers to the damage caused to an aircraft or its components due to the presence of foreign objects. Ingestion of bolts, formation of ice, and ingestion of rocks are all examples of foreign objects that can cause FOD. However, the failure of internal parts is not considered a cause of FOD. FOD typically occurs when foreign objects come into contact with the aircraft during operation, causing damage to its structure or systems. Internal part failures, on the other hand, are typically caused by mechanical or electrical issues within the aircraft itself, rather than external objects.

The primary silencers on an aircraft noise suppressor are positioned against the aircraft fuselage. This means that they are located next to or in contact with the outer structure of the aircraft.

A preflight inspection is a flight preparedness check conducted before each flight to ensure that the aircraft is in proper condition and ready for operation. It involves a thorough examination of various components, systems, and documentation to verify their functionality and compliance with safety regulations. This inspection is crucial for identifying any potential issues or discrepancies that could affect the safety and performance of the aircraft during flight. Therefore, preflight is the correct answer as it accurately represents the inspection conducted to ensure flight preparedness.

The thrust stand sliding into position on tracks allows for flexibility when running an engine that has been removed from the airframe. This feature allows the engine to be securely positioned and tested while providing the ability to adjust its position as needed.

The correct answer is Engine monitoring system (EMS). This system is used on most modern jet engines to gather and record engine data. It allows for real-time monitoring of various engine parameters such as temperature, pressure, and fuel consumption. This data is then recorded and analyzed to ensure optimal engine performance and detect any potential issues or malfunctions. The EMS plays a crucial role in maintaining the safety and efficiency of jet engines.

Aircraft power plant and engine intermediate maintenance technical orders (TO) contain troubleshooting charts. These charts provide a step-by-step guide to identify and resolve issues with the power plant and engine systems. They help maintenance personnel diagnose and fix problems efficiently by providing a systematic approach to problem-solving. Troubleshooting charts typically include a series of questions or steps to follow, leading the user to the most likely cause of the issue and suggesting appropriate corrective actions.

When operating an engine that is installed on an aircraft, it is important to position the aircraft so that the wind is blowing directly into the inlet, within ±45°. This is because the inlet is designed to take in air for the engine's combustion process, and having the wind blow directly into the inlet helps to ensure a proper air-to-fuel mixture. Additionally, positioning the aircraft within ±45° allows for some flexibility in wind direction while still maintaining an effective airflow into the engine.

The turbine area should be checked for foreign object damage (FOD) prior to operation on the test cell facility. This is because the turbine area is a critical component of the engine and any foreign objects, such as debris or particles, can cause damage and affect the performance and safety of the engine. Therefore, it is important to inspect and ensure that the turbine area is free from any FOD before operating the engine.

When using a vibration analyzer, a preset signal is exceeded, the user will be notified by a flashing channel indicator light emitting diode (LED).

Transient engine vibration refers to vibrations that occur intermittently or sporadically, rather than persistently. These vibrations may come and go, and are typically caused by temporary factors such as changes in engine load or operating conditions. Unlike resonance vibrations, which occur at specific frequencies, transient vibrations do not have a consistent pattern or frequency. Similarly, externally excited vibrations are caused by external factors such as road conditions or wind, whereas transient vibrations can originate from within the engine itself.

The tachometer generator is a device that measures the speed of an engine. It generates a frequency signal that is proportional to the engine speed. Therefore, the correct answer is "engine speed" as the frequency of the tachometer generator directly corresponds to the speed of the engine.

Complete loss of lubrication is the most common cause of bearing failure. Bearings rely on lubrication to reduce friction and prevent excessive heat and wear. Without proper lubrication, the bearing surfaces can become damaged, leading to failure. Transient vibration, partial loss of lubrication, and stall condition over temperature can also contribute to bearing failure, but complete loss of lubrication is the most significant factor.

Both fixed and portable test cell noise suppressors use water to cool the exhaust gases. This means that regardless of whether the suppressor is a permanent installation or a portable unit, water is used as a cooling mechanism for the exhaust gases.

Turbine blade fatigue failure does not result from blends. This means that the blending process used in manufacturing turbine blades does not contribute to their fatigue failure. Fatigue failure is typically caused by repeated stress and strain on the blades over time, leading to cracks and eventual failure. Nicks, dents, and scratches can potentially weaken the blades and contribute to fatigue failure, but blends do not have this effect.

Dry motoring is the correct answer because it allows you to start the jet fuel starter (JFS) without advancing the throttle to idle or supplying fuel to the aircraft engine. Dry motoring is a procedure used to test the JFS and ensure its proper functioning without actually starting the engine. This check is important for safety and maintenance purposes.

The correct answer is the Data Collection Unit (DCU). The DCU is responsible for collecting and storing data from various components of the engine monitoring system, including the Engine Diagnostic Unit (EDU). It then transfers this information to the Ground Station Unit (GSU) for analysis and monitoring. The DCU plays a crucial role in ensuring that the engine is functioning properly and any issues or abnormalities can be detected and addressed in a timely manner.

If oil is observed on the turbine wheel or oil smoke is seen at or near the turbine section during a test cell run, it is a good indication of a damaged aft bearing oil seal. This suggests that there is a problem with the seal that is allowing oil to escape and potentially causing the smoke. It is important to address this issue to prevent further damage to the turbine system.

If an engine stalls or surges during a test cell run, the variable stator vanes should be investigated. Variable stator vanes are components in a gas turbine engine that help control the airflow and optimize engine performance. If these vanes are not functioning properly, it can cause disruptions in the airflow, leading to engine stalls or surges. Therefore, it is important to examine the variable stator vanes if such issues occur during a test cell run.

Engines are mounted from a cradle mount. This means that the engines are suspended or supported by a cradle-like structure. This method of mounting allows for stability and ease of testing, as the engines can be securely held in place while measurements and assessments are conducted.

Engines that have been involved in an incident or a mishap need to be tested in addition to determining the condition of a repaired or overhauled engine. This is because these engines may have suffered damage or experienced abnormal conditions during the incident or mishap, and it is important to ensure that they are still in proper working order before being used again. Testing these engines helps to identify any potential issues or damage that may have occurred, allowing for necessary repairs or further investigation to be conducted.

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A portable test cell is a mobile unit used for testing engines or other equipment. It is not equipped with a control cab, which is a separate compartment for operating the test cell. It also does not have a thrust trailer, which is used for measuring the thrust produced by the engine. Additionally, it does not come with a miscellaneous equipment kit, which could include various tools and instruments needed for testing. The correct answer is the hydraulically operated pylon mount cradle, which is a device used for mounting the engine or equipment being tested.

Before moving an aircraft into the hush house, it is necessary to inspect the aircraft and its forms. This means that not only the physical condition of the aircraft needs to be checked, but also any necessary paperwork or documentation related to the aircraft must be reviewed. This ensures that the aircraft is in proper working order and all necessary paperwork is in place before it is moved into the hush house.

Bearings are used to support the fan and low-pressure turbine. Bearings are mechanical components that reduce friction between moving parts and support the weight of rotating shafts. In this case, bearings are used to support the fan and low-pressure turbine, allowing them to rotate smoothly and efficiently. Bushings, brackets, and blades are not specifically designed for this purpose and would not provide the necessary support and functionality.

Periodic inspection checklists are used as an aid in test facility inspections. These checklists provide a systematic and comprehensive approach to inspecting the test facility, ensuring that all necessary areas and equipment are inspected. They help to ensure that inspections are conducted consistently and efficiently, and that all required inspections are completed. By using periodic inspection checklists, test facility inspectors can identify any potential issues or deficiencies and take appropriate corrective actions.

The combustion inlet temperature is not measured in a jet engine. Temperature measurements are typically taken at the exhaust gas, turbine inlet, and fan turbine inlet. The combustion inlet is the location where fuel is introduced into the engine, and measuring the temperature at this point is not necessary for engine operation or monitoring.

The correct answer is "an electric magnetic-drag-type instrument." This means that the tachometer indicator is an instrument that uses electricity and a magnetic drag mechanism to measure and display the speed of rotation of a motor or engine. This type of tachometer is commonly used in vehicles and other machinery to provide accurate and reliable speed readings.

Excessively high breather pressure in an engine test cell is usually an indication of damage to engine bearing oil seals. This is because damaged oil seals can cause an increase in pressure within the engine's breather system, leading to the high pressure readings on the gauge. This issue can result in oil leakage, reduced engine performance, and potential damage to other engine components.

During vibration analysis, the amplitude is measured in mils. One mil is equal to 0.001 inch. This means that when measuring the amplitude of vibrations, each mil represents a thousandth of an inch. Therefore, the correct answer is 0.001 inch.