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QuestionAnswer
How is oxygen separated from other gases in the air? By compressing and cooling the air
Why must aviator’s breathing oxygen be “bone dry”? To ensure operation of oxygen system components. Oxygen with a high moisture content would freeze at high altitudes, causing the oxygen system to be inoperative
List some of the warning signs of hypoxia. Blurred vision, slight shortness of breath, a vague weak feeling, light dizziness.
What is the maximum pressure at which low-pressure gaseous oxygen cylinders are charged? 450 psi m.
What color are low-pressure gaseous oxygen cylinders painted? Yellow
How are oxygen tubes color-coded? With bands of green and white cellulose tape
What two types of connections are used in a low-pressure oxygen system? Pipe-thread and flared-tube connections
What component reduces system pressure in a high-pressure gaseous oxygen system? A pressure-reducer valve
What construction methods prevent high-pressure gaseous oxygen cylinders from shattering? Heat-treated alloy wrapped with steel wire
What are the two main types of oxygen regulators? The continuous-flow and pressure-demand type
What’s a disadvantage of the continuous-flow regulator as compared to other types? Wastes oxygen
The MD–1 oxygen regulator can be used with what types of oxygen systems? With high- or low-pressure gaseous or liquid oxygen systems
In an emergency the pressure-demand regulator can supply oxygen to what altitude? 50,000 feet
What should system pressure be during an operational check of a regulator? Near normal operating pressure
Explain how the molecular sieve bed operates. Nitrogen in the air is absorbed in one bed of molecular sieve while oxygen passes through the bed. When the molecular sieve becomes saturated, the concentrator vents the nitrogen overboard
What happens if the MSOGS concentrator fails? It will turn on an OXYGEN caution light in the cockpit and automatically switch to the backup oxygen supply.
What’s the temperature of liquid oxygen? –297 °F.
Why should liquid oxygen never be sealed, capped, or trapped in a container without a relief-valve? It will rupture the container
What factors are used to determine converter size? The number of crew, mission duration, and the type of oxygen regulation equipment used
What’s the probable cause if frost appears on the outside of a LOX container? Vacuum loss
How are pressure control valves controlled? Spring-loaded bellows
What’s the primary purpose of the pressure-closing valve? To maintain a constant head pressure on top of the liquid oxygen in the storage container
What’s the normal position of the pressure-opening valve? Closed
Why is it important to ensure there is no moisture in the fill, buildup, and vent valve? It may freeze in the vent position.
In what position should you manually place the buildup/vent valve during a filling operation? VENT position
How are the check valves in quick disconnects operated? Automatically
What are the two modes of operation in the supply sequence of the liquid oxygen system? The economy mode and demand mode
What technical manual covers the requirements for LOX systems inspection? –6 technical manual for the specific aircraft
What is the purpose of a bleed air system? To operate or control pneumatic systems or components
What are the three sources of bleed air used for system operations on jet aircraft? Aircraft engine(s); ground air cart; and gas turbine compressors, gas turbine units, or auxiliary power units
What equipment provides bleed air when the aircraft is on the ground with the engine shutdown? A ground air cart
List the components of a bleed air system. Check valves, shutoff valve, wing isolation or body crossover valves, flow control valves, pressure regulating valves, bleed air ducting, and the necessary controls
What is the purpose of a ground-air-connection check valve? Prevent the escape of bleed air from the system
What material is usually used for high-pressure/high-temperature ducting? Stainless steel
What action should you take to ensure a good airtight seal when installing a V-band clamp? Tap around the circumference of the clamp as its tightened
Why should you install the bottom bolts on a bolted flange duct first? This forms a cradle and holds the gasket in place while you install the remaining bolts
Besides stainless steel, what other materials can be used in the construction of medium-pressure/medium-temperature ducting? Titanium to aluminum alloy
What type lubricant can be used on beaded duct sleeves to aid in installation? Water only
Where in the aircraft is molded fiberglass ducting used for distributing conditioned air? Cabin area
What’s the purpose of gaskets? To make an airtight seal with most types of flange connections
What devices are installed in bleed air systems to compensate for thermal expansion of ducting? Expansion joints (bellows), thermal compensators, universal joints, loops, horseshoe bends, and offsets
What’s the most important reason for insulating ducts? To prevent heat damage to structural members, electrical wiring, and combustible material, as well as hydraulic, oxygen, and fuel lines
What type of insulating material is fireproof? Fiberglass fabric blankets
What is the purpose of the rubber accordion boot wrapped around the duct between the sections of the insulation? This boot allows for differences in expansion rates of the duct and insulation
What’s used to lace the studs together in a metal foil blanket? Wire
What are the most common types of duct damage? Scratch, minor dent, major dent, and gouge
Define gouge. A defect wherein the surface of the material is cut or removed sufficiently to cause the duct wall thickness to be reduced
Which bleed air duct system is subjected to the highest pressure/temperature? High-pressure/high-temperature
What should you do anytime you locate a non-permissible leak in the high-pressure/high-temperature section of the bleed air system? Inspect the aircraft structure in the immediate area of the leak for heat damage
What is air conditioning? The simultaneous control of temperature, humidity, and air distribution within a space
Does heat always move to cold or does cold always move to heat? Heat always moves to cold
While the aircraft is in flight, what controls the flow of ram air to the primary heat exchanger(s)? Moveable ram air inlet and/or exit doors that modulate in flight
During low airspeeds or ground operation what induces cooling airflow to the primary heat exchangers when there is not enough ram air to cool the primary heat exchangers? Ejectors
What consists of a centrifugal air compressor and an expansion turbine, and is often known as a “pack”? Air cycle machine (ACM)
Why would some of the outlet air from the primary heat exchanger need to bypass the air cycle machine? If cabin temperature controls call for warmer air
What component provides an additional stage of cooling after the bleed air has left the primary heat exchanger and, if required, the air cycle machine? Secondary heat exchanger
What is the primary purpose of the refrigeration bypass valve? To prevent water from freezing in the water separator
What component uses centrifugal force to remove moisture in the air that is caused by rapid cooling? The water separator
What two forms of energy are essentially interchangeable? Pressure and temperature
What happens to heat of the engine bleed air as it passes through the primary heat exchanger(s)? Some of the heat is transferred to ram air
What happens to the pressure of the engine bleed air as it passes through the primary heat exchanger(s)? Almost no change
What happens to the air as it enters the compressor of the air cycle machine? The pressure increases and, therefore, the temperature increases
What results in a very large decrease to the air within the air cycle machine? As the air expands across the turbine, the pressure decreases greatly. The pressure decrease, coupled with the energy extracted to drive the compressor, results in a very large decrease in temperature
What are the two methods of cooling used in a typical bootstrap system? (1) By transferring heat to the ram air, or (2) removing most of the heat by expanding it and converting it into work to drive the compressor
The refrigeration bypass valve opens so that warm air can mix with the air in the water separator if the water separator’s outlet air temperature falls below what temperature? 38 °Fahrenheit
Explain the difference between preconditioned and conditioned air Once the air has cycled through the entire system with the exception of the water separator, it is called preconditioned air. Preconditioned bleed air becomes conditioned air when it has made its way through the water separator
What percentage of the earth’s atmosphere is nitrogen? 78 percent
List the three pressurization ranges. Unpressurized range, isobaric range, and differential range
What is the isobaric range? 8,000 to 21,000 feet above sea level
Where does the differential range extend? From where the isobaric range stops to the maximum altitude of the aircraft
What component opens and closes to control the amount of air leaving the aircraft’s pressurized area? Outflow valve
What is the approximate atmospheric pressure at sea level? 14.7 psi
The aneroid is fully expanded and the metering valve closed at what specific altitude? 8,000 feet
What two pressures are applied to the differential diaphragm? Control and atmospheric pressure
What section of the pressure regulator protects the crew from too fast a rise in cabin pressure? The rate control section
In addition to a regulator, two outflow valves, and a pneumatic relay, what other component is a part of the dual-differential regulator? Dump valve
What component operates as a safety valve if the regulator fails? Outflow valve
Why are two outflow valves used on aircraft with large crew areas? Because of the large volume of air to be relieved
How can the dump valve be operated in case of electrical power failure? Manually
What are the three features of the pressure controller? Isobaric, differential, and rate controls
How is isobaric control maintained? Adjusting spring tension
What types of pressure act on the differential controller’s diaphragm? Control head and atmospheric
How is the rate control orifice size adjusted? Rate control knob
During a dive, what prevents damage caused by reverse flow of atmospheric air? The ball check valve
Describe the purpose of the manual control valve. It’s used to manually set and regulate the control pressure if the automatic cabin pressure controller fails
What happens if the pressure regulator test handle remains in the TEST position? The aircraft will pressurize on the ground
Where are fire detectors normally placed on aircraft? On conventional aircraft they are placed in the engine and baggage compartments. On jet aircraft they are placed on the engine section, nacelle, or tail cone
How are the thermal switches connected? In parallel with each other, and in series with the warning light
What are the two types of thermoswitches? FENWAL® switch and Iron Fireman switch
How do the FENWAL® and Iron Fireman detector switches operate? The inside of the switch has a low coefficient of expansion, while the shell has a high coefficient of expansion. When they are heated, they will expand and contact will be made
What are two precautions you must take when handling thermal switches? Before, during, and after installation, take precautionary measures to ensure that the shell is not dented, distorted, or otherwise damaged. Be cautious when handling these units because the shell is the actuating mechanism. Never handle the shell with pl
What causes a thermocouple fire detector system to activate? A rapid rate of temperature increase beyond normal engine warm-up
What are the three circuits in the thermocouple fire warning system? The detector, alarm, and test circuits
How are the thermocouples connected in respect to each other? In series
What does a photoelectric detector cell consist of? A glass envelope, which is coated on the inside with infrared-sensitive lead sulfide
The amplifier of a photoelectric fire detection system is sensitive to what frequencies? Between 7 and 60 Hz
How can you distinguish the fire warning light from the overheat light in the photoelectric fire detection system? The overheat light flashes, and the fire warning is steady
What are fire detector sensing loops made of? A center conductor embedded in a semiconducting compound enclosed within a tube
How do liquid agents extinguish fire? By excluding oxygen from the fire area
How will an insufficient nitrogen charge affect agent discharge? The cylinder won’t have enough pressure to discharge properly
What shape are aircraft fire extinguisher containers? Spherical
What prevents leakage between the bonnet assembly and container during discharge? A rubber O-ring packing
How are squibs fired? Applying 28 VDC to the squib
What is incorporated in some two-shot systems to delay electrical current to the bonnet assemblies? Time delay relay
What does a flashing red light in a fire emergency control handle (T-handle) indicate? An overheat
What steps should be taken to remove liquid fire extinguishing agents if moisture or high temperature was present? (1) Purge the area and surface with clean, dry air. (2) Clean the affected areas with applicable cleaning solution and rinse with clean, fresh water. (3) Drain the excess water and dry the area with cloths, paper towels, or air pressure no greater than
What is usually found at the lowest point of a fuel tank? A sump and a drain
What is installed in fighter aircraft fuel tanks that prevent fuel sloshing and reduce the potential for fuel ignition or explosion if the aircraft is hit by enemy fire? Foam block
Which fuel tank type is made of a rubber or nylon material and conforms to the shape of the vacant cavity within the fuselage where it sits? Bladder-type (fuselage)
Which type of fuel tank is not removable and is not self-sealing? Integral (wing)
What is the primary purpose of a centrifugal pump? Pressurize the fuel manifold
What distinct advantage do centrifugal-type pumps have over other types of pumps? They tend to run cooler because there is no contact between the rotating impeller and the stationary housing of the pump body
Why must the centrifugal-type pump be installed at a location where fuel will flow to the pump’s inlet? Because the centrifugal-type pump is not self-priming
How are centrifugal-type pumps driven? Hydraulic power or electricity
Which pump consists of an electric motor and a shaft with circular vanes at the end? Rotary vane-type pumps
When would a rotor vane-type pump most likely be used? Scavenging operations
What principle applies to the operation of an ejector pump? Venturi
What is the function of the rotor in an air-refueling pump? To remove fuel vapors caused by the centrifugal force of the impeller
List two types of check valves. Flapper and pressure-loading
What is the purpose of the small-drilled hole in the center of the flapper? Allows some fuel to return from other parts of the system to lubricate a dry pump
How are pressure-loaded check valves opened? By pump pressure only
Why are shutoff valves installed in a manifold? To control the flow of fuel or air through a manifold or into a tank
What is an advantage of the sliding gate shutoff valve? It has the advantage of being able to control a large flow of fuel
What components make up a rotary plug shutoff valve? Valve body, and the motor and rotor plug
What type of seal is used between the disc and valve body of a disc type shutoff valve? O-ring
What is the purpose of a fuel-level control valve? Provides for the automatic control of the fuel level during the filling of a fuel tank
Piston-type fuel level control valves operate on what principle? Hydromechanical
How is the diaphragm-type valve controlled? Electrically
During fuel transfer or refueling, what are the four functions of the low-level shutoff valve? (1) Close and prevent fuel from being transferred out of the tank even though the tank is pressurized (by energized operation of the solenoid). (2) Open and allow fuel to transfer out of the tank (by de-energized operation of the solenoid). (3) Close an
What controls the operation of the fuel control valve in a combination fuel control valve and pilot valve? The pilot valve
What condition may cause a temporary malfunction of a vent float valve? Frozen condensation within the valve
What is the definition of a switch? A component used to open or close an electrical circuit or to select paths through the circuit
List three types of fuel-controlled switches. Pressure, float, and fuel-flow indicator
How does a pressure switch work to indicate fuel pressure? If there is sufficient fuel pressure in the manifold, the diaphragm actuates the micro switch, which completes the electrical circuit across the terminal and illuminates a pressure indicator light to indicate fuel pressure.
How are float switches actuated? By fuel level
What switch indicates a flow or no flow condition? Fuel-flow indicating switch
List two types of fuel quantity indicating switches. The DC liquid-level and capacitance-type
What type of fuel quantity indicating system uses the potentiometer wiper mechanism? The DC liquid-level type
The capacitance-type fuel indicating system shows how much fuel is in a tank, using what form of measurement? Pounds of fuel
What component controls the amount of pressure entering a fuel tank? Air pressure regulator
If the air pressure regulator fails, what unit will relieve the excess pressure? The pressure/vacuum relief valve
What item of a disconnect coupling prevents fuel leakage from an installed external tank? An O-ring
What is the purpose of the aircraft fuel system? Stores fuel and delivers the proper amount of clean fuel at the right pressure to meet the demands of the engine
What are the four components of the engine feed system? Pumps, check valves, shutoff valves, and thermal relief valves
If a pump fails to operate, what component prevents the reverse flow of fuel through the pump? Check valve
What controls all shutoff valves in an engine feed system? Throttles
What is the purpose of thermal relief valves? To relieve pressure from heat-expanded fuel
What is the purpose of the crossfeed system? To ensure fuel is supplied to the engines at all times
What are the three methods used to transfer fuel? Pump, air pressure, and gravity flow
What component controls fuel level in the receiving tank during fuel transfer? Fuel level control valve
How is a fuel control valve controlled? Either by the solenoid or the pilot float
What components are required during gravity transfer of fuel? Shutoff valve and float valve
Where are vent ports located? Top of the fuel tank
Describe the purpose of the fuel pressurization system. The system is designed to maintain air pressure in the tanks to minimize fuel boiling and, in some cases, to transfer fuel
What system is used to remove residual fuel from a manifold? Scavenge
Define fueling. The filling of a tank or tanks with fuel from an external source
What is the most common method used to refuel an aircraft? Single-point
During refueling, when all tanks are filled, what happens to the fuel pressure? It increases
What is the fuel servicing safety zone? It is the area within 50 feet of a pressurized fuel carrying servicing component; and 25 feet around aircraft fuel vent outlets.
What grounding procedures must be followed to properly ground the fuel truck and the aircraft during a defueling operation? The aircraft and fuel tank must be bonded together and connected to a low-resistance ground
Name two advantages of having aerial refueling capabilities. Greatly extends the range of the aircraft and permits takeoffs with much greater loads than would otherwise be possible
How is the aerial refueling receptacle operated and controlled? Operated hydraulically and controlled electrically
Name the principal contaminants that reduce the quality of fuel. Water, foreign particles, microbial growth, and sediment
List some of the problems that water in the fuel can cause. Free water can cause icing of the aircraft fuel system, usually in the aircraft boost-pump screens and low-pressure filters. Fuel gage readings may become erratic because the water short-circuits the aircrafts electrical fuel cell quantity probe. Large am
List some of the most common types of foreign particles that can show up in fuel. Rust, sand or dust, aluminum and magnesium compounds, brass shavings, and rubber
Which color of rust indicates magnetic particles? Black
Sediment in fuel appears in what forms? Dust, powder, fibrous material, grains, flakes, or stain
What are the two categories of sediment? Coarse and fine
Define fine sediment. Particles smaller than 10 microns
Name two measures you can take to ensure that you do your part in keeping a clean fuel supply. Any two: Don’t drag fuel hose nozzles on the ground. Keep dust caps on. Do not dump hydraulic fluid, oil, or any other substance besides fuel into bowsers. Immediately close and lock bowser lids when dumping is complete. Cap disconnected fuel lines when p
Why is classification of fuel leaks necessary? To differentiate between those leaks that constitute a flight safety hazard and require repair before flight, and those that do not require immediate repair
What must you use to wipe down a fuel leak? Wipe the area dry with a clean, static-free, absorbent cloth to assist the drying process
How many leak categories are there and what are they? 4; Class A, B, C, and D
When in doubt about which class a fuel leak is, what should you do? Classify it to the next highest category
What are the five leak location identified for fuel leak evaluation purposes? External, internal vented, internal non-vented, electrical conduit, and external mounted components
What is determined when crossing the leak category with the leak location? Condition/action
In addition to AFTO form 781A or 781K, what form must you document fuel leaks if automated data systems are not available? AFTO Form 427, Aircraft Integral Fuel Tank Repair Historical Record
When the opening of a filled balloon is closed, why is there no action on the balloon? Because the pressure of the gas inside the balloon is exerted equally in all directions
What type of energy does a falling object possess? Kinetic energy
Can energy pass from potential to kinetic and back to potential? Yes
What is Newton’s first law of motion? A body at rest remains at rest, and a body in motion continues to move at a constant speed in a straight line, unless acted upon by an external force
What is Newton’s second law of motion? An unbalanced force on a body produces, or tends to produce, an acceleration in the direction of the force, and that acceleration is directly proportional to the force and inversely proportional to the mass of the body
Which law of physics best explains how a jet engine produces forward thrust? Newton’s third law of motion
State Bernoulli’s principle. When the speed of a stream of gas increases, the pressure of the gas decreases; and when the speed of the gas decreases, the pressure increases
When a jet engine reaches idle speed, what determines how the fuel control regulates engine speed? Power lever setting
What two forms of energy does a jet engine produce? Thrust and heat
Approximately what percent of the energy produced by the fuel is needed to maintain the jet engine operating cycle? 60
Where is the point of highest pressure within a jet engine? In the diffuser section
On a jet engine that does not have an afterburner, where is the point of highest temperature? In the combustion section
Where is the point of highest airflow velocity in a jet engine? At the ejector nozzle
What is the purpose of the turbine stator? To increase the velocity of the gases striking the turbine blades
After the gases leave the turbine section and enter the exhaust section, what type of velocity do they have? Axial
What straightens the flowpath of gases in the exhaust case? The vanes in the exhaust case
In a multistage turbine, what is the arrangement of the shafts? One shaft is hollow, allowing the other shaft to operate inside it
Which turbine drives the front compressor on a dual-spool engine? The rear turbine
What is a turbojet engine? An air-dependent, thermal, jet propulsion device.
Name the three main sections of a gas turbine engine. Compressor, combustion chamber, and turbine.
What are the two types of compressors used in jet engines? Centrifugal and axial-flow.
How do pressure pulsations in a centrifugal compressor present themselves? As shock waves or irregular movement of air through the compressor.
What effect do pressure pulsations have on a compressor? Rapidly reduced efficiency.
Why is it not desirable to use multiple-stage centrifugal compressors to increase the pressure ratio? Because of the complicated construction and increased weight of the engine that would result.
What two needs stimulated the development of the axial-flow compressors? More power and a more economical engine.
How does the air pass through an axial-flow compressor? The air travels rearward along the axis of the engine, and the air pressure is increased at each stage of compression.
How are axial-flow compressor rotor blades similar to an aircraft propeller? They both are airfoil-shaped and move an air mass.
What is the purpose of the stationary vanes that are located behind each rotor wheel in the single-spool axial-flow compressor? They direct the air onto the blades of the succeeding rotor wheel and also cause the air pressure to increase.
How are the compressor rotor blades and stator vanes arranged in a multiple-stage, axial-flow compressor? The rotor blades are graduated from long to short through the stages of compression. The stator vanes are also graduated in size to correspond in length with the rotor blades.
Identify two reasons the dual-spool axial-flow compressor was designed. Ease of starting and reduction of compressor stalls.
What unit determines the speed of the N2 (high-pressure) rotor in a dual-spool compressor? The fuel control
Which type of compressor is more durable, the axial-flow or the centrifugal? Centrifugal
Why is getting good combustion in a gas turbine engine so complex? Because the fuel and air must combine rapidly, the combustion process must not use excessive energy and space, and the combustion chamber must not overheat
What is “combustion efficiency”? A measure of the ability of the combustion chamber to burn the fuel completely and to mix the elements thoroughly with the remainder of the air charge before the gases reach the turbine nozzle
How is combustion efficiency computed? By comparing the heat energy received by the air as it passes through a test combustion chamber with the known energy that was added to the chamber in the form of fuel
What are two by-products of combustion? Carbon deposits and carbon monoxide
What are the two purposes of the combustion section? To burn the fuel and to deliver the resulting gas to the turbine at a temperature that does not exceed a predetermined limit for the particular engine in use
What is the approximate air-to-fuel ratio used for the actual burning process in a combustion chamber? 15:1
Name the three types of combustion chambers. Can, annular, and can-annular
What supports the annular-type combustion chamber in the front and rear? The front of the chamber is attached to the burner support, and the rear of the chamber is supported on the outside by the stator blade support ring of the first-stage turbine and on the inside by the stator inlet ring of the first-stage turbine
How does the additional air that is required to support combustion and cool the annular combus-tion chamber reach the chamber walls? Through elongated slots and round holes in the sections of the chamber walls
What supports the can-annular combustion chambers within the combustion section on certain engines? Fuel nozzles in the front and turbine nozzle case at the rear
What is the purpose of a fuel nozzle? To introduce fuel into the combustion chamber
Multiple-fuel nozzles are used for what two purposes? To handle large quantities of fuel with even distribution and to minimize the variation that might be caused by a clogging of any one of the nozzles
In a dual-orifice type of fuel nozzle, fuel is injected into the engine combustion chamber from which orifices for high-engine-thrust operation? Both the primary and secondary orifices
Name the three types of turbines. Impulse, reaction, and reaction-impulse
What type of turbine design is used on most jet engines? Reaction-impulse.
What is inserted between the rotating blades on multiple-stage turbines? Stationary turbine nozzle vanes
What characteristics and values must be considered when designing turbines? Exhaust gas flow rate, shaft RPM, turbine inlet and outlet temperatures and pressures, turbine exhaust velocity, and the required power output
What is the most frequently used method of attaching the turbine blades to the rotor disc? The fir tree method.
Describe the “fir tree attachment.” A series of grooves and notches broached in the rim of the turbine rotor disc
What three types of fasteners are used to secure the turbine blades to the rotor disc? Steel pins, lock strips, and rivets
What are the two principal turbine blade configurations? Shrouded and unshrouded
What three things does the shroud on shrouded turbine blades do? Reduce blade vibration, improve airflow, and increase engine efficiency
The term “exhaust duct” refers to what? The engine exhaust pipe (or tailpipe) connecting the turbine outlet and the jet nozzle of a non-augmenter engine
What are two purposes of the engine exhaust duct? To collect and straighten the gas flow that comes from the turbine and to increase the velocity of the gases before they are discharged from the exhaust nozzle
What may occur if you alter the exhaust nozzle? Changes in engine performance and exhaust gas temperature
Why are small tabs placed in the engine exhaust nozzles of some engines? To correct exhaust gas temperature
An augmenter is classified as what type of an engine? A ramjet engine
What is the purpose of a variable area orifice at the augmenter exhaust nozzle exit? To schedule the nozzle area to obtain the desired thrust within the safe operating limits of the engine
What effect should augmenter operation have on engine operation? None
Define the term screech. A condition of periodic violent pressure fluctuation in the augmenter duct, resulting from cyclic vibration due to the unsteady release of combustion energy
What two parts will most likely deteriorate or fail if moderate or severe screech is not checked? The flameholder or augmenter duct
How is screech controlled? By placing screech liners in the augmenter duct
What two things does the flameholder in the augmenter do? Creates local turbulence and reduces the gas velocity in the vicinity of the flame
What are two drawbacks of the turbojet engine? Inefficient fuel use when flown below Mach 2 speeds and the amount of noise they generate
What makes the turbofan engine more desirable than basic turbojet engines? Capable of turbojet performance at higher speeds, while maintaining the shorter take-off capability offered by the turboprop engine
What are the major sections of a turboprop engine? Reduction gearbox assembly, a torquemeter assembly, and a gas turbine power section
What devices reduce the potential for engine flameout? Compressor bleed valves, variable-pitch stator blades, surge dampeners, variable inlet guide vanes, and other devices
What does a “rich blowout” mean? An overrich mixture flameout
What types of fuel controls do most modern aircraft use? Either a hydromechanical, electrohydromechanical, or a “unified” fuel control
What factors affect the hydromechanical fuel control operation? Engine air inlet temperature, compressor discharge pressure, turbine RPM, and power lever angle
What fuel control system uses a computer such as a digital electronic engine control (DEEC), digital engine control (DEC), or an electronic engine control (EEC) for primary fuel-flow control? An electrohydromechanical system
What component regulates and distributes fuel for the most efficient engine operation at all power settings? Fuel pumps
What component provides a leaner fuel mixture for engine starting? The fuel derichment valve
What valve drains the fuel manifold on shutdown? Pressurizing and dump (P&D) valve
What are the principal purposes of an oil system? Clean, cool, and lubricate
What gives a visual indication of oil level on some oil tanks? Sight gauges
Classified as to function, what two basic pumps are used in a jet engine oil system? Pressure pump and the scavenge pump
Classified as to structure, what three types of pumps are used most often in jet engine oil systems? Which of these three is the most common? Gear, gerotor, and sliding vane; gear type
How do air/oil coolers cool the oil? By passing hot engine oil through the core of the cooler and passing ram air over the core
How do fuel/oil coolers cool the oil? By having fuel flowing into the tubes of the cooler and oil flowing around the fuel-filled cooler tubes
What are the two types of oil nozzles? Restrictive tube and internal passage
What is the purpose of oil system seals? To prevent the loss of fluid
List three types of oil seals used in jet engines. Synthetic, labyrinth, and carbon
What two items should you check prior to replacing seals? The cure date and part number
Define Cure date. The date of manufacture of the seals
Define Packing. A component designed to provide a seal between two moving parts or to provide a running seal
Define Gasket. A component designed to provide a seal between two stationary parts
What two factors are essential for jet engine starting? The engine must be motored to an RPM that provides sufficient air for combustion and after this starting combustion, the engine must be accelerated to the point where the power developed by the turbine is adequate for a self-sustaining operation
What are the four types of starters typically found on Air Force aircraft? (1) Air turbine (impingement), (2) pneumatic, (3) cartridge-pneumatic, and (4) gearbox-system starters
What is meant when it is said that the cartridge-pneumatic starter is self-contained? Self-contained implies that the starter has the ability to start the engine without the use of ground support equipment.
In a gearbox-type starter system, what connects to the engine gearbox and turns the engine compressor by way of a vertical gear shaft (tower shaft)? A power takeoff (PTO) shaft
What are the three types of ignition systems discussed in this lesson? An AC system, a DC system, and a high-energy capacitor type
In the engine ignition system the AC voltage is stepped up to approximately how many volts by high-ratio transformers? 20,000 volts
What are the main parts of a direct-current ignition system? A vibrator, a transformer, and igniter plugs
What function does the vibrator unit in the DC ignition system perform? It changes the 28 volts of direct current into a pulsating current so that the voltage may be stepped up through the transformer
What is the purpose of having two complete high-energy capacitor-type ignition systems on each engine? Safety—if one fails, you have another system as a redundant backup
What component provides high-temperature spark for engine starting? Igniter plug
In addition to being light in weight and small in size, what other requirement must aircraft instruments meet? Easy to read
Oil pressure indicators measure pressure in what unit of measurement? Pounds per square inch (PSI)
What positions can be selected by the oil temperature select switch? Individual engine temperatures (1, 2, 3, 4, etc.), maximizing (M), and TEST (T)
How is a tachometer powered? By a tachometer (tach) generator
What does an N1 gauge typically indicate? The low-pressure compressor speed in percent RPM
What does the EPR system for each engine consist of? Pressure probes, a transducer unit, and an engine pressure ratio indicator
How is engine fuel-flow measured? Pounds per hour (pph)
What dissimilar metals are used in thermocouples? Alumel and chromel
What is used to analyze oil samples and determine the identity of metal particles worn from oil-wetted parts? Spectrometric oil analysis
What are the three major benefits of the Joint Oil Analysis Program (JOAP)? (1) Improved safety (2) Reduced maintenance cost (3) Increased equipment availability
What are the three basic techniques for taking a sample? (1) Dip tube sampling (2) Drain/valve sampling (3) Pump/syringe sampling
Why should you never use mouth suction to fill the sampling tube? Many fluids are highly toxic and may cause paralysis and/or death
When taking an oil sample how full should you fill the bottle? Fill to approximately ½ inch from the top
If you have to cut a sampling tube to make it the correct length, how should it be cut? Cleanly at a 45 degree angle
At a minimum, what personal protective equipment must you wear when taking a JOAP sample? Goggles and gloves
What problem most frequently affects sample integrity? Contamination
What are the two categories of oil samples that you may be required to take? Routine and special
What TO gives instructions on how to fill out a DD Form 2026? 33–1–37–1, Joint Oil Analysis Program Manual
Created by: theredstar