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Powerplant Oral
FAA
| Question | Answer |
|---|---|
| what is the purpose of dynamic dampers in crankshafts? | Reduce engine vibrations |
| what type of bearings are generally found in reciprocating engines? | plain, ball and roller bearings. |
| are the connecting rods used in each cylinder of a radial engine the same? explain | no, radial engines use master and articulating rods |
| name the different types of piston rings, | oil control rings, compression rings, and oil scrapper rings |
| where should piston ring gaps be installed relative to each other and why? | compression rings gaps should be staggered so they do not align, this will prevent excessive blow by. |
| what could result from incorrectly installing piston rings? | excessive oil consumption |
| what purpose do oil control rings serve? | they regulate the thickness of the film on the cylinder walls |
| what is used to help prevent valve surge or floating in an aircraft engine? | two or more springs are used in each valve |
| on engines equipped with hydraulic valve lifters, what should the valve clearance be? | the valve clearance should be zero |
| what is the purpose of valve overlap? | it allows for better volumetric efficiency and lower cylinder operating temperatures |
| what indications are given in the event of a leaking or open primer while the engine is running? | the engine will not idle properly. |
| a cold cylinder is found when troubleshooting a running engine, what does this indicate? | no combustion in that cylinder |
| when pulling a propeller through, a hissing sound is heard indicating blow by, what procedure should be performed next? | a compression check should be performed to identify the faulty cylinder |
| what is the purpose of performing a compression test? | to determine if the valves, piston and piston rings are sealing properly |
| when an engine is overhauled, how is its total time affected? when an engine is rebuilt, how was its operating history affected? | when rebuilt by manufacturer, total time is allowed to start over from zero. when engine overhauled, total time continues. |
| what inspections should be performed after a propeller strike without sudden stoppage? | inspect engine mounts, the crankcase and the nose section for damage, inspect the oil and oil filters/ screens for metal, inspect crankshaft or driveshaft for cracks and misalignment |
| name some of the precautions that should be performed prior to engine removal, | disconnect battery, turn off the fuel valves, chock the wheels and if necessary install a tail stand. |
| when inspecting a piston, where are cracks more likely to be found? | in those areas that are highly stressed, usually the base of the piston bosses, inside the junction of the bore and the walls, and the ring lands |
| what does it mean if an engine part is within serviceable limits? | it means that the part is within manufacturer serviceable limits, it does not need replacement |
| what tools or instruments are use to inspect a cylinder barrel for out of roundness? | a dial indicator, or an inside micrometer, or a telescopic gage with a micrometer, or a bore gage. take two measurements at 90 deg. apart |
| how can a loose stud in an engine crankcase be repaired? | remove the loose stud and inspect the hole for size and thread condition, it may be necessary to use an oversized stud or Heli coil insert. |
| what publications is used to check engine for normal operation | manufacturers maintenance manual. |
| a weak cylinder is found during a compression check, what must be inspected? | pressure is transmitted equally in all directions |
| what purpose does an oil analysis serve? | metal particles in the oil show normal and abnormal wear of the engine, this helps in evaluating the engines internal condition |
| what inspections should be performed on an engine that has been in storage? | perform an inspection to determine if there is any corrosion damage. |
| where would a carburetor air temperature bulb be located? | in the ram air intake duct |
| what is the fuel pressure range in a float type carburetor? | 3-5 psi |
| name the basic components in a fuel indicating system, | the transmitter and the indicator |
| what unit of measure is generally used to indicate fuel flow? | pounds or gallons per hour |
| why is fuel flow monitored? | to determine fuel flow consumption and engine performance |
| what does the manifold gage indicate and how is it calibrated? | it measures the absolute pressure in the engine manifold and is calibrated in inches of mercury |
| what directly controls manifold pressure? | throttle opening and engine RPM |
| during engine operation, where should the propeller control be set when checking manifold pressure? | low pitch high RPM |
| is the aircraft electrical system required to power a cylinder head temperature gage? | no, a thermocouple is used as the electrical source |
| what are the possible indications of an oil pressure transmitter or indicator malfunction? | a severe or sudden drop in oil pressure when the oil temperature remains normal and the oil supply remains full |
| what does a tachometer indicate in a reciprocating engine? | it indicates engine RPM |
| where should the thermocouple be installed on a reciprocating engine using a single probe cylinder head temperature system? | in the hottest cylinder |
| explain the main differences and advantages of turbofan over turbo jet engines | turbo fan engines uses a fan to bypass some air around the engine core and to provide thrust, the advantage is this produces additional thrust without increasing fuel flow. |
| name the major components in a gas turbine engine | air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox and accessory section |
| what determines the amount of airflow through a turbine engine | the forwards speed of the aircraft, compressor speed and air density |
| name two types of compressors commonly used in turbine engines | axial and centrifugal flow compressors |
| name two different methods for attaching turbine engine rotor blades to their main rotor discs | dovetail type root or bulb type root or fur tree type root |
| what is a split compressor system? | also called dual or twin spooled compressors, these are connected to the turbine section with two rotor shafts, one inside the other |
| what are the different types of combustion chambers used inside turbine engines? | can, annular, can-annular and reverse flow annular |
| what prevents the combustion chambers from burning? | cooling air along the inside of the liner |
| what is the purpose of the interconnecting tubes attached between can type combustion chambers? | for flame propagation during start |
| what functions do axial flow turbine nozzles perform? | direct mass airflow to drive the turbine rotor at a specific angle |
| how is thermal stress relieved in a thermal disc? | by directing bleed air onto the face of the disc or by grooves being cut in the disc |
| what are carbon seals used for in turbine engines? | they are used as oil seals for the rotor shaft bearings |
| what is shaft horse power? | it is an indication of the torque developed by a turboprop or turbo shaft engine |
| name the main components of a typical APU | a small power turbine for power and bleed air and an electrical generator |
| what is the greatest demand placed in an APU | when supplying bleed air |
| how is an APU generally started? | with its own electrical starter and battery |
| where does the APU get its fuel supply? | from the aircrafts main fuel tanks |
| at what speed does a gas turbine APU operate and how is the speed maintained? | at or near rated speed regardless of electrical or pneumatic loads, the APU fuel control automatically adjusts the fuel flow to maintain rated speed |
| what is used to prevent a heavily loaded APU from exceeding its maximum EGT | a load control valve modulates the pneumatic load to maintain the EGT within limits |
| how is an APU shut down and why is this procedure used? ... cooling down period, damage could occur as a result of thermal shock | after the APU is unloaded by closing the main air bleed valve, it is run for a specified amount of time to allow the EGT to cool and stabilize, this cooldown period is typically three minutes, if a heavcily loaded APU is abruptly shut down without any... |
| what powers the variable guide vanes used in some APUs to regulate compressor intake flow? | fuel pressure |
| what is fan blade shingling? | it is the overlap of the mid spin shrouds of the fan blade |
| when a turbo fan or turbojet engine is shut down, what should a mechanic listen for during coast down? | any rubbing sounds or other unusual noises from the engine |
| why are compressor washes performed and what methods are commonly used? | to remove any contaminants from the compressor section and improve engine performance, the fluid wash and abrasive grit wash are commonly used |
| how can you tell if a turbo fan or turbo jet engine is out of trim? | there will be a high EGT at the target engine pressure ratio for exhaust power |
| name the different types of compressor blade damage that may be found during inspections | dents, cracks, galling, pitting, scratches, burrs and gouges |
| what kind of markers can be used to mark the parts in the hot and cold sections during repair? | layout dye, a felt tip marker or chalk. |
| how does relative humidity affect turbine engines | has little to no effect |
| what criteria determines replacement of life limited turbine engine components? | cycles, hours, and or calendar time |
| if turbine blades are removed from turbine discs, why should they be installed in the same location? | to maintain the balance of the turbine wheel |
| how are gas turbine engine tachometers calibrated? | they are calibrated in percent RPM |
| on a turbine engine, what is the engine pressure ratio and what does it indicate? | it is the ratio between the total inlet pressure and total exhaust pressure and is used to indicate the thrust developed by the engine |
| on a turbine engine, what does EGT indicate and how is it obtained? | EGT is the average temperature of the exhaust gases, and it is obtained by thermocouples placed near the turbine exit |
| can the EGT system on a turbine engine be checked without running the engine? | Yes, by checking the resistance of the thermocouples and circuits |
| name three components of a induction system of a reciprocating engine | air scoop, carburetor or fuel control, and the intake manifold. |
| what could happen if the induction system becomes obstructed? | the engine may not be able to produce its rated power or it may not run at all, this may also be an indication of a dirty air filter |
| how does induction icing affect engine performance? | it causes a reduction in power and possible erratic operation |
| how is induction icing categorized? | as impact ice, fuel evaporation ice and throttle ice |
| what is the common method used to prevent induction system ice in reciprocating engine? | raise the temperature of induction air with a preheater |
| what causes fuel evaporation ice? | fuel evaporation ice is formed because of the decrease in the air temperature resulting from evaporation of the fuel after it is introduced into the airstream |
| is carburetor throttle ice more likely to occur at a higher or lower power setting? why? | at a lower power setting because the throttle is partially closed, offering a larger surface area for ice accumulation |
| what may be the indication of a leaking intake pipes? | the engine runs rough at low RPMs |
| what happens to engine power when the carburetor heat is applied? | there is a noticeable drop in power |
| what could happen if carburetor heat is applied at high engine power settings? | detonation |
| what are two types of supercharged induction systems? | internally driven and externally driven |
| how and at what point does an internally driven supercharger boost pressure? | an engine driven impeller compresses the air fuel mixture after it leaves the carburetor |
| what is used to power a turbocharger? | engine exhaust gas directed onto the turbocharger turbine |
| what could result if the waste gate in a turbocharger system does not close fully? | the engine may not be able to produced its rated power at certain altitudes and the aircraft may not be capable of reaching critical altitude |
| what function does a turbocharger wastegate perform? | it controls the amount of exhaust gas either into or around the turbocharge thus controlling boost pressure of the turbocharger |
| whet could cause a turbocharged engine to surge? | there could be waste gate or controller malfunction |
| what are the most common ways to control a wastegate? | either mechanically with linkages through the throttle or a separate control or by an actuator that is driven by oil pressure |
| in a pressurized reciprocating aircraft, what component in the turbocharger system is used to limit the airflow used for cabin pressurization? | the sonic venturi |
| what is the function of a divergent shaped jet engine inlet during subsonic flight? | it causes air velocity to decrease with a subsequent increase in air pressure |
| where are bell mouth inlet ducts typically found? | on helicopter engines |
| how are venturi type particle separators found on many turbine powered helicopters function? | a venturi is used to accelerate the flow of incoming air and debris through a curved intake, the debris gains too much inertia to allow it to follow the curved intake toward the engine and is channeled away from the compressor |
| what are the most common methods used for anti icing for of a turbine engine inlet ducts? | engine bleed air and electric heating elements |
| what is the purpose of the exhaust system? | to remove high temperature gases |
| name two types of reciprocating engine exhaust systems | the short stack and the collector system |
| what drawback in using collector type exhaust systems is more than offset when used on turbocharged engines? | the loss of horsepower due to exhaust system backpressure |
| what could result if the internal baffles or diffusers in an exhaust system fail? | the flow of exhaust gases can be restricted resulting in a loss of engine power |
| what type of exhaust system is used on turbocharged systems | the collector system |
| what kind of material is normally used to make shrouds found in the exhaust system? | stainless steel |
| how do you inspect internal baffle sand diffusers of an exhaust system? | by disassembling the exhaust system as necessary and visually inspecting the exhaust components |
| why is an exhaust system failure considered as a severe hazard? | it can result in carbon monoxide poisoning, loss of engine power, or fire |
| what could happen if flood, sink, or galvanized marks are made on an exhaust system? | they can cause corrosion to the structure which could result in cracks when heated |
| what happens if the heat exchanger leaks exhaust gases into the induction system? | there is a loss of engine power |
| what is an indication of an exhaust gas leak? | a flat gray or sooty black deposit in the area of the leak |
| where are the most common places to find cracks in the exhaust system? | at welded or clamped areas and at the flanges |
| what is a common cause of turbocharger wastegate sticking? | coke deposits or carbon build up |
| why are turbocharged exhaust system leaks very damaging at high altitudes? | pressure differential will cause the leak to escape with torch like intensity |
| what are exhaust system coke deposits? | excessive carbon buildup |
| what is the result of changing the exhaust nozzle area of a turbine engine? | the engines performance and exhaust gas temperature change |
| name the components of a typical turbine engine exhaust nozzle | the tail cone exhaust ducts and support struts |
| what is the purpose of thrust reverses? | they help decelerate the aircraft after landing? |
| how does a noise suppressor found on older turbojet engines work? | converts low frequency sound which is audible over great distance into high frequency sound thus reducing the sound footprint |
| what are the two most commonly used types of thrust reversers? | the clamp shell or mechanically blocked, and the cascade or aerodynamically blocked |
| how much do thrust do the thrust reversers produce compared to the engines full forward thrust? | substantially less (35-50 percent of forward thrust) |
| what are the hazards of operating some thrust reversers at low ground speeds? | ingestion of foreign objects stirred up by the exhaust gases and re ingestion of exhaust gases |
| what are some of the sources used to heat the fuel in a turbine engine fuel system? | bleed air and engine lubricating oil |
| what are the most common types of fuel metering systems used on small reciprocating engines? | float type carburetors, pressure injection carburetors, and direct fuel injection systems |
| what function does the mixture control perform? | it controls the fuel air mixture |
| what generally causes spark plug fouling? | operating the engine at an excessively rich mixture at idle |
| what is the purpose of an accelerating system? | it provides an immediate but brief increase in fuel flow in the venturi to enrich the mixture |
| what is a carburetor economizer system? | it is a power enrichment system that provides a richer mixture at higher power settings where the excess fuel aids in engine cooling, this system functions as throttle setting above cruise power |
| when the mixture is placed in the idle cut off position, a slight rise in RPM is noted prior to the engine decelerating, what does this indicate? | the idling system is working properly |
| why should engine RPM be accelerated periodically when making carburetor adjustments? | to clear the engine |
| what maintains the fuel pressure in a pressure injection carburetor? | an engine driven pump |
| what happens if the manual mixture control of a pressure injection carburetor is moved to the idle cut off position? | the engine stops |
| how does an automatic mixture control, AMC, function? | a sealed brass bellows connecting to the fuel metering system, expands and contracts with the changes in pressure and temperature, adjusting the mixture accordingly |
| what are some of the advantages of fuel injection systems over carbureted systems? | less danger of induction icing, better acceleration, better fuel distribution, better fuel distribution, better fuel economy, reduced overheating of individual cylinders |
| what purpose do turbine engine fuel control units serve? | they automatically meter fuel to the engine |
| what are the two basic types of turbine engine fuel control units? | hydromechanical and electronic |
| what are the engine variables detected by the fuel control unit? | power lever position, engine RPM, compressor inlet temperature, compressor inlet pressure, discharge pressure burner pressure |
| what are the two major components of a supervisory electronics engine control? | the electronic control unit computer and the hydromechanical fuel control |
| what are some of the advantages of a full authority digital engine control (FADEC) over a a hydro mechanical fuel control?.. more repeatable engine transients | better fuel economy, improved starts, requires no engine trimming, provides engine limit protection, provides constant idle speeds regardless of atmospheric conditions or bleed air requirements, fully modulates the active clearance control, and allows... |
| what do turbine engine fuel spray nozzles do? | the inject fuel into the combustion area |
| what are the different engine indications used for trimming an aircraft | either EPR or RPM is used depending on the particular engine |
| what maintenance adjustments are normally allowed on an installed hydromechanical fuel control? | specific gravity for fuel, idle RPM, maximum RPM or maximum EPR |
| what type of fuel pump can vary the amount of fuel discharged regardless of speed? | variable displacement pump |
| what is used to keep water, sediment and foreign matter out of the carburetor? | the main fuel strainer |
| what is the purpose of a pressure relief valve in a constant displacement pump? | it returns excess fuel that is not required by the engine to the inlet side of the pomp |
| what type of engine driven fuel pump is widely used other than gear or piston pumps? | a rotary vane type pump |
| what function do fuel boost pumps perform? | they supply pressurized fuel to the fuel pump which helps prevent vapor lock and cavitation |
| what is a commonly used type of fuel boost pump? | the centrifugal type |
| what causes vapor lock and why is it a concern? | vapor lock is caused by insufficient fuel pressure , high fuel temperatures, and excessive fuel turbulence, which may completely block any fuel flow resulting in engine failure |
| what function does the engine driven pump on a turbine engine perform | it provides a continues supply of fuel at the proper pressure while the engine is running |
| name the two categories of turbine engine pumps | constant and variable displacement |
| what category is a gear type pump classified in? | constant displacement |
| when performing an external inspection of an engine driven fuel pump, what should you look for? | leaks and security of mounting |
| what is the purpose of the sheer section of a dual element constant displacement pump? | if one of the elements seizes a portion of the driveshaft seizes, allowing the other element to continue operation |
| where in a turbine engine fuel section is ice formation likely to occur and how is it prevented? | the fuel filter is most susceptible to ice formation, so a fuel heater is used that consists of a heat exchanger, using either engine oil or bleed air to warm the fuel |
| what is the purpose of a bypass valve in an engine duel system micron filter? | it is a safety feature that allows fuel to flow to the engine if the filter becomes blocked |
| what is the purpose of a duplex fuel nozzle | duplex fuel nozzle discharges two different spray patterns, it is wider during startup and acceleration and narrows when the engine speed increases above idle |
| what are the functions of the pressurizing and dump portions of a pressurizing and dump valves? | the pressurizing portion provides primary and secondary fuel flow to dual line duplex fuel nozzles and the dump portion allows fuel to drain from the manifolds after engine shut down |
| what purpose do fuel selector valves serve? | they allow tank and engine selection and provide means for shutting off fuel flow |
| how can the remaining service life of starter generator brushes be determined? | by visually inspecting the amount of wear groove remaining on the brushes |
| what components of the starter generator require periodic inspection? | commutator and brushes should be inspected for wear beyond operational limits |
| between field and armature windings in started generators, which ordinarily receive current for operating in the start mode? | generally both fields and armature receive current in the start mode |
| what are possible sources of low pressure compressed air used for starting jet transport aircraft equipped with air turbine starters? | a ground power unit (GPU), an on board APU, compressed bleed air from an already started engine |
| when should ignition ideally occur? | a specific number of degrees as described by the manufacturer before the piston reaches top dead center on the compression stroke |
| why are dual magnetos used in engine ignition systems? | to improve combustion efficiency and provide redundancy for safety |
| why is magneto timing so important? ...must be electrically aligned with a particular cylinder | for an engine to run properly the spark plug and the cylinder have to fire at a specific time to produce the energy for the spark at the required time, the magneto must be in the e-gap position, the breaker points must start to open and the distributor.. |
| what function does a magneto perform? | it produces a high voltage that forces a spark to arc across a spark plug gap |
| name the components of a high tension magneto system | a permanent multipole rotating magnet, soft iron core, soft iron, and pole shoes |
| name three main circuits of a high tension magneto system | magnetic, primary and secondary |
| what is an e-gap angle? | it is a point a few degrees beyond the neutral position of a rotating magnet where maximum magnetic fields exist |
| what reduces arcing in the points and also aids the collapsing of the magnetic field in a magneto? | a capacitor |
| how does a magneto produce the high voltage required to fire a spark plug?... secondary coil | in the rotating cycle when the magneto rotor is in the e-gap position, the primary points open which interrupts the current flow in the primary circuit causing a higher rate of flux change in the core, and introducing a pulsing high voltage in the... |
| what is the p-lead and how does it function? | the p-lead connects to the ignition switch to the primary circuit of the magneto, when the ignition switch is turned to the left position, the right magneto is grounded so that only the left magneto operates and vice versa |
| what is magneto timing light used for and what does it indicate? | it is used for both internal magneto timing and magneto to engine timing and indicates the exact instant the magneto points open |
| why are turbine engine igniters generally not susceptible to carbon fouling? | because the high energy sparks they produce clean off any deposits on the firing end |
| what is the function of a duty cycle in relation to a turbine ignition system? | a duty cycle allows the operation of the ignition system for a given amount of time and is then followed by a minimum specified cooling down period |
| what are the three main component of a turbine engine ignition system? | ignition exciters, high tension leads, igniters |
| when the engine is operating, what does an ammeter/load meter indicate when connected to 1. battery positive lead. 2. generator output lead | when connected to the positive battery lead, the ammeter indicates whether the battery is charging or discharging, when connected to the generator output lead it indicates the current produced by the generator or electrical system load |
| what is done to ensure that each generator shares the load in a multiple generator system? | the generators are paralleled |
| where would you find generator rating and performance data? | on the data plate attached to the generator |
| how is the voltage of a dc generator controlled? | by varying the field current strength |
| what is the most common type of alternator used in most aircraft AC systems? | the three phase alternator |
| how does a voltage regulator control the voltage of an alternator? | by regulating the voltage output of the DC exciter |
| what does the speed of rotation and the number of poles of an alternator determine? | the frequency of the alternator output |
| what are some methods used to maintain 400hz alternator output frequency on large turbojet or turbofan engines? | constant speed drives, integrated drive generators, and variable speed constant frequency power systems |
| name the major parts of a DC motor | the armature, field, brushes and frame assembly |
| name the components of a direct cranking starter system | an electric motor, reduction gears, and automatics engaging and disengaging mechanism |
| name three types of DC motors | series, shunt, and comppount |
| what types of DC motor is commonly used for a reciprocating engine starter and why | a series wound motor is commonly used because it has high starting torque under heavy loads |
| what are the operating modes of a turbine engine starter generator? | it first operates as a starter then as a generator once the engine is running |
| what is the possible indication when a starter drags? | a dirty or worn starter commutator |
| where would wire with high temperature insulation be used? | when they run close to high temperature areas such as exhaust stacks or heating ducts |
| what is the size standard for electrical wire used in US manufactured aircraft? | the American wire gauge AWG |
| how are wire sizes represented? | by numbered gauge size, the smaller wires are represented by larger numbers. the smallest wire normally used in aircraft is 22 gauge |
| what is the maximum slack allowed between the supports of a single wire or bundle installation? | not over half an inch |
| why are wires bonded on power plant installations? | to provide a current return path for electrical accessories and to prevent static discharge |
| a reciprocation engine is found to have excessive oil consumption without evidence of any oil leaks, what is the likely cause? | the piston rings are worn or broken |
| what are the functions of lubricating oils in reciprocating engines? | to reduce friction between moving parts and to remove heat |
| name two important characteristics of aircraft engine oil | the oil must be light enough to circulate freely yet be heavy enough to provide the proper oil film at engine operating temperatures |
| what could happen to an oil that is too low a viscosity at normal engine operating temperatures? | the oil may become so thin that the oil film between moving parts is easily broken resulting in premature wear |
| what are some of the factors that must be considered by the engine manufacturer in determining the proper grade of oil for a particular engine | the operating load and temperature, as well as the rotational speed |
| why do aircraft reciprocating engines use relatively high viscosity oil? | because they usually have high operating clearances and operate at high temperatures and pressures |
| name some oil contaminants | metal particles, dirt, carbon, moisture and acids |
| what is a possible indication of low oil pressure together with high oil temperature? | a low or inadequate oil supply |
| in ash less dispersant AD oils, what function does the dispersant perform? | the dispersant causes sludge forming materials to repel each other and remain in suspension until they can be trapped by the oil filter or drained, this keeps the oil passages and ring grooves free from harmful deposits and the inside of the engine clean |
| why do oil reservoirs have expansion space? | to provide for oil foaming, thermal expansion, and air in the return oil |
| what could cause oil foaming? | diluted oil, contaminated oil, and the oil level being too high |
| what controls oil pressure in a gear type oil pressure pump? | an oil pressure relief valve |
| what function does an oil cooler bypass valve perform? | it directs oil either through the cooler or around it in order to perform proper operating oil temperatures |
| what could be a possible indication if the oil cooler passage becomes abstructed? | a high oil temperature |
| where is the oil temperature bulb usually located? | at the engine oil inlet |
| what does the presence of metal particles in an engine oil filter indicate? | depending on the size and type of the metal particles this usually indicates abnormal wear and possible internal failure |
| what should be done if metal particles are found in the engine oil filter? | follow the engines manufacturers maintenance instructions |
| where is the most critical point of lubrication in a gas turbine engine? | at the turbine bearings |
| what type of oil is used in a turbine engine oil system? | synthetic oil |
| where are oil screens or filters most likely located in a turbine engine oil sytem? | at the oil pressure system, main filter, scavenge system, and at or just before the oil jet |
| name two types of turbine engine oil coolers | air cooled and fuel cooled |
| what could happen to an oil that is too low a viscosity at normal engine operating temperatures? | it may become so thin that the oil film between moving parts is easily broken resulting in premature wear |
| what effect does excessive heat have on reciprocating engines? | it shortens the life of the engine parts, changes the behavior of combustion and impairs lubrication |
| what is the purpose of cooling fins? | they provide a larger cooling surface area for removing heat from the cylinders heads of air-cooled reciprocating engines, airflow around the cooling fans transfers the heat from the cylinder heads into the air |
| what are the reasons for using engine cowlings, baffles, and cowl air seals? | the cowling performs two main functions: it streamlines the engine area to reduce drag and is used together with the baffles and cowl air seals to direct airflow over the cylinders for cooling |
| what is the purpose of cowl flaps and how are they operated? | they are used to control the amount of airflow through the cowling, they are either mechanically, electrically or hydraulically operated |
| how does an augmented cooling system work? | an outer tube placed over the existing exhaust gas creates a venturi effect that draws more airflow over the engine thus providing additional cooling |
| where should cowl flaps be positioned during ground operations? | fully open |
| what type of power is used to operate cowl flaps? | manually, hydraulic, or electrical |
| what should be done when cooling fin damage is discovered? | depending on the scope of the damage, some cooling fins may be repaired subject to the manufacturers overhaul and repair limitations, if an excessive amount of cooling fin is broken off the cylinder should be replaced |
| why is cowl flap adjustment important? | the movement must be within tolerances to keep cylinder head temperature within allowable limits |
| how are turbine engines cooled? | they are cooled by air passing through the engine, about 75% of the air passing through the engine is used for cooling, which leaves 25% for combustion, this air is used to cool the combustion chamber and turbine |
| in a turbine engine, where does bleed air come from that is used to cool bearings in other parts? | the engine compressor |
| what is the relationship between turbine engine upward temperature limits and power produced? | the higher the combustion temperatures that an engine can withstand without damage, the more power it is capable of producing |
| what is the approximate percentage of air passing through a turbine engine that is used for cooling rather than combustion? | approximately 75% |
| what can be done to effectively allow higher gas temperatures in the turbine section of some engines? | compressor bleed air ducted through hollow sections in the turbine inlet guide vanes and first stage rotor blades can lower temperatures enough to prevent heat damage |
| what type of fire detector systems are used for engine fire detection? | overheat, rate of rise, and flame detectors |
| how does a thermal switch fire protection system operate? | when heated past a predetermined temperature, the switch closes causing the warning device in the cockpit to activate |
| how many thermal switches are needed in a thermal switch fire protection system? | at least one |
| what kind of fire detection system allows more complete coverage than a spot type system? | a continuous loop system |
| what happens if an engine equipped with a thermocouple fire warning system overheats slowly? | nothing because a fast temperature rise or rapid heating is required for this type of fire system to operate |
| what electrical power is required for a thermocouple fire protection system to operate? | both thermocouple produced power and aircraft electrical system are required for this type of fire protection system to operate |
| what is the likely cause of a false warning? | the engine fire sensing loop is bent or kinked excessively |
| what are fire extinguishing system designed to do? | the are defined to dilute the oxygen levels around the engine to a point that does not allow combustion or to reduce temperatures below the ignition point |
| what elements must be present for a fire to occur? | an ignition source such as heat or a spark, fuel and oxygen |
| what group of fire extinguishing agents are no longer manufactured because of environmental concerns? | halons or Freon, or CFCs were no longer manufactured after 1995, however existing stocks of CFC may still be used and are subject to strict handling and disposal regulations |
| how are fire extinguishing agents distributed? | through perforated tubing and or discharge nozzles |
| what is the purpose of the discharge cartridge and how is it activated? | the discharge cartridge, or squib, which is electrically ignited, fires a projectile into the fragile disk, thereby releasing the fire extinguishing agent |
| how is a fire extinguisher system with a high rate of discharge classified? | as an HRD fire extinguishing system |
| what do the red and yellow disks in a fire extinguishing system indicate? | a yellow disk indicates normal discharge, a red disk indicates thermal discharge |
| how is the fire extinguishing agent in a HRD system distributed, and how long does it take to discharge? | the agent is distributed through a series of high pressure tubes and it takes 1-2 seconds to discharge |
| what is the purpose of a pressure gage in a fire extinguishing system? | it indicates pressure within the container to check if the pressure is within limits, a pressure temperature chart is used |
| what is the function of a propeller? | the prop blades create thrust to push or pull an airplane through the air |
| what is the difference between a fixed pitch prop and a controllable pitch prop?... propellers also provide reverse pitch and feathering | a fixed pitch prop is one that has a built in angle that cannot be changed by the pilot, a controllable pitch propeller is one that can be changed by the pilot and is usually controlled by a governor that maintains a constant speed, some controllable... |
| how are some wooden propellers blades protected from wear and damage? | by metal tipping fastened to the leading edge and tip |
| what happens to the blade angle of a constant speed propeller during a constant power dive? | the blade angle increases to prevent an overspeed |
| what are the functions of a constant speed prop governor? | it boosts engine oil pressure before it enters the prop hub , it senses rotational speed of the prop and then adjusts the oil flow to the propeller hub to change pitch and therefore speed of the prop |
| what is the purpose of a propeller counter weight? | centrifugal force acting on the counterweights causes the blade angle to increase |
| what is meant when a propeller governor is in an on speed condition? | the governor is not accelerating or decelerating and the speed or spring and flyweight forces are in balance |
| how is a constant speed feathering propeller feathered?.. controlled by the pilot moving the propeller control into a feathering detent | by releasing oil pressure in the governor, the counterweight and featherings spring move the propeller into feather, this happens automatically if the governor pressure drops to zero, following an engine failure in most turbo props or can be manually... |
| what is an unfeathering accumulator? | it is an oil accumulator used to provide oil pressure to unfeather a propeller |
| what is an alpha range and a beta range and where are they found?.. operating in the zero or minimum thrust range and negative thrust or reverse thrust mode which is usually on the ground | the alpha range and beta rangers pertain to the operating modes of a turbo prop reversible pitch propellers, in the alpha range the propeller is operating in the standard constant speed mode, which is usually in flight, in the beta range the prop is.. |
| what systems are commonly used for prop ice control? | fluid or alcohol and electrical heat applied to the propeller blades root |
| what propeller repairs can be performed by a certified mechanic with a power plant rating? | only minor repairs and alterations can be performed by a powerplant mechanic, major repairs can be performed by the manufacturer or certified repair station, the props man. maint. manual outlines the scope of repairs |
| how are wooden props generally cleaned? | with a brush or cloth and warm water with a mild soap |
| where would you find the correct method and technique for cleaning an aluminum prop and hub? | the prop manufacturers maintenance instructions |
| what type of non destructive testing should be accomplished to a propeller after blending? | the procedure recommended by the manufacturer |
| what are the two criteria used by many manufacturers to determine the amount of bent damage that can be repaired by cold bending an aluminum prop? | the extent of the bend and its blade station location |
| how can repair file marks be removed from an aluminum propeller?` | with very fine sand paper |
| when performing a static balance on a two liter prop, what positions must the prop be placed in when measurements are taken? | vertical and horizontal positions |
| what is a propeller protractor used for? | is used for measuring propeller blade angle |
| what blade condition can cause engine vibration? | vibration can be caused by a prop being out of track and or balance as well as incorrect blade angle setting |
| what is blade tracking? | blade tracking is a procedure that compares the positions of the propeller blade tips relative to each other |
| what controls both manifold pressure and RPM on an engine equipped with a fixed pitch propeller? | the throttle |
| what publications can be used as a guide for 100 hr inspections on aircraft engines?` | manufacturers maintenance manuals and FAR pt.43 App. D |
| how do you identify the engine serial number? | it is located on the engine data plate |
| prior to returning a reciprocating engine to service after a 100hr inspection, what operational checks must be performed? | check the power output, static and idle RPM, check magnetos, fuel, and oil pressure, cylinder and oil temperature check |
| where are life limited parts of an engine listed? | engine maintenance manuals, TCDS, and the air worthiness limitations section of instructions for continued airworthiness |
| where can engine operating limits be found? | engine manual, engine specifications, TCDS, and aircraft manufacturers maintenance manual |
| why are hot section inspections performed on turbine engines? | to determine the integrity and wear of the hot secti0on components |
| what inspections must be performed following a turbine engine overspeed? | refer to the engine manufacturers maintenance manual for the required procedures |
| what inspections must be performed on a turbine engine if the exhaust gas temperatures exceed limitations? | a hot section inspectiopn |
| what FAA approvals are required when installing an engine that is not in the aircraft type certificate? | an STC or an FAA field approval |
| under what condition is compliance with an engine service bulletin mandatory? | when an air worthiness directive references a service bulletin or when compliance is part of the approved operating specifications for a commercial or air carrier operator, when engine or component overhaul require compliance at time of overhaul |
| what are the possible causes for a turbo jet or turbofan engine having high exhaust gas temperature, low RPM, and high fuel flow at all engine pressure ratios | turbine damage or loss of turbine efficiency due to wear |
Created by:
cordon.gabriel
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