Orals Flashcards
What is the purpose of dynamic dampers on crankshafts?
The reduce engine vibrations
What type of bearing are generally found in reciprocating engines?
Plain, ball, roller.
Are the connecting rods used in each cylinder of a radial engine the same? Explain.
No radial engines use master and articulating rod assemblies
Where should piston ring gaps be installed relative to each other and why?
Compression ring gaps should be staggered so that they do not align. this prevents excessive blow by
What could result from incorrectly installed piston rings?
Excessive oil consumption.
What purpose do oil control rings serve?
They regulate the thickness of the oil film on the cylinder walls
What is used to help prevent valve surge or floating in an aircraft engine?
2 or more springs are used on each valve
On engines equipped with hydraulic valve lifters, what should the running valve clearance be?
Zero
What is the purpose of valve overlap?
It allows better volumetric efficiency and lowers cylinder operating temperatures
Name the different types of piston rings
Oil control, compression and oil scraper
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 valve blowby. What procedure should be performed next?
compression check should be performed to identify the faulty cylinder
What is the purpose of performing a compression test?
To determine if the valves, pistons and rings are sealing properly
When an engine is overhauled, how is its total time affected? When an engine is rebuilt, how is its operating history affected?
The total time on the engine must be continue and the time since major overhaul is entered into the engine log. If the manufacturer rebuilds the engine, it is granted a zero time status and is considered to have no previous operating history.
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 particles. Inspect the crankshaft or driveshaft for cracks and misalignment
Name some of the precautions that should be performed prior to engine removal.
Disconnect the battery, turn off the fuel valves, chock the wheels, install a tail stand if necessary
When inspecting a piston, where are cracks most likely to be found?
In those areas that are highly stressed; usually the base of the piston bosses, inside at 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 the manufacturers limits and can be used in an engine
What tools or instruments are used to inspect a cylinder barrel for out of round?
A dial indicator or inside micrometer is usually used to measure the top of the cylinder and at the skirt. A telescopic gauge and micrometer can also be used. two reading should be taken 90 degrees from each other.
How can a loose stud in an engine crackcase be repaired?
Remove the loose stud and inspect the hole for size and thread condition. It may be necessary to use an oversize stud or Helicoil insert.
What publication is used to check an 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 inspection 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 on float type carburetors?
3 to 5 psi
Name the basic components of a fuel indicator 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 consumption and engine performance.
What does the manifold gauge 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 e set when checking the manifold pressure?
low pitch, high rpm
Is the aircraft electrical system required to power a cylinder head temperature gauge?
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 while the oil temperature remains normal and the oil supply remains full
What does a tachometer indicate on a reciprocating engine?
Engine RPM
Where should the thermocouple be installed on a reciprocating engine using a single probe cylinder head temperature system?
On the hottest cylinder
Explain the main difference and advantage of turbofan over turbojet engines
A turbofan uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides 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 forward speed of the aircraft, compressor speed, and air density
Name the two types of compressors commonly used in turbine engines
Dovetail type root, bulb type root, fir tree type root
What is a split compressor system?
Also called dual or twin spool compressors, these are connected to the turbine section with two rotor shafts, one inside another
What are the different types of combustion chambers used in 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?
They direct the mass airflow to drive the turbine rotor at a specific angle.
How is thermal stress relieved on a turbine 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 horsepower?
It is an indication of the torque developed by a turboprop or turboshaft engine
Name the main components of a typical APU
A small power turbine for power and bleed air and an electrical generator.
When is the greatest demand placed on an APU
When supplying bleed air
How is an APU generally started?
With its own electrical starter and battery power
Where does the APU get its fuel supply?
From one of the aircraft’s main fuel tanks
At what speed does a gas turbine engine APU operate and how is this speed maintained?
At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the 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 EGTs within limits
How is an APU shut down and why is this procedure used?
After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period is typically three minutes. If a heavily loaded APU is abruptly shut down without any cool down period, damage could occur as a result of thermal shock.
What powers the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?
Fuel Pressure
What is fan blade shingling?
It is the overlapping of the midspan shrouds of the fan blade
When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?
Any rubbing sound 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 turbofan or turbojet engine is out of trim?
There will be a high EGT at the target engine pressure ratio for takeoff power.
Name the different types of compressor blade damage that may be found during inspection
Dents, cracks, galling, pitting, scratches, burrs, burns, gouges
What kind of markers can be used to mark the parts in a hot and cold sections during repair?
Layout dye, felt tip marker, chalk
How does relative humidity affect turbine engines?
Negligible effect
What criteria determines replacement of life limited turbine engine components?
Cycles, hours and or calendar time
If turbine blades are removed rom the turbine disc, why should they be reinstalled in the same location?
To maintain the balance of the turbine wheel
How are gas turbine engine tachometers calibrated?
They are calibrated in percent of RPM
On a turbine engine, What does exhaust gas temperature indicate and how is it obtained?
EGT is the average temperature of the turbine discharge gases and is obtained by thermocouples placed near the turbine exit.
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 turbine exhaust pressure and is used to indicate the thrust developed by the engine
Can EGT system on a turbine engine be checked without running the engine?
Yes it can be checked by the resistance of the thermocouples and circuits
Name the three components on the induction system of a reciprocating engine
The 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 rate power or it may not run at all. This may also be an indication of a dirty air inlet filter.
How does induction icing affect engine performance?
It causes 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 a recip engine?
Raise the temperature of induction air with a preheater.
What causes fuel evaporation ice?
Fuel evap ice is formed because of the decreases in 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 partly closed, offering a larger surface area for ice accumulation.
What may be the indication of leaking intake pipes?
The engine runs rough at low rpm
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 air pressure?
An impeller compresses the fuel/air 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 on a turbocharger system does not close fully?
The engine may not be able to produce its rated power at certain altitudes, and the aircraft may not be capable of reaching critical altitude.
What function does a turbocharger waste gate perform?
It controls the amount of exhaust gas either into or around the turbocharger, thus controlling the boost pressure of the turbocharger.
What could cause a turbocharged engine to surge?
There could be a waste gate or controller malfunction
What are the most common wats to control a waste gate?
Either mechanically with linkages to 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 amount of turbocharger airflow used for cabin pressurization?
A sonic venturi
What is the function of a divergent shaped jet engine inlet during subsonic flight?
It causes the air velocity to decrease with a subsequent increase in air pressure.
Where are bellmouth inlet ducts typically found?
on helicopter engines
How do venturi type particle separators found on many turbine powered helicopters function?
A venture 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 towards the engine, and is channeled away from the compressor.
What are the most common methods used for anti icing of turbine engine inlet ducts?
Engine bleed air and electric heating elements.
What is the purpose of the exhaust system?
To remove high temperature noxious gases
Name two types of recip engine exhaust systems
The short stack and collector system
What drawback in using collector type exhaust systems is more than offset wen used on turbocharged engines?
The loss of horsepower due to exhaust system back pressure
What could result if the internal baffles or diffusers in an exhaust system fail?
The flow of the exhaust gases could be restricted, resulting in a loss of engine power
What type of exhaust system is used on turbocharged engines?
The collector system
What kind of material is normally used to make the muffler shrouds found in the exhaust system?
Stainless Steel
How do you inspect the internal baffles nd diffusers of an exhaust system?
By disassembling the exhaust system as necessary and visually inspecting the components.
Why is an exhaust system failure considered a severe hazard?
I can result in carbon monoxide poisoning, loss of engine power, or fire
What could happen if lead, zinc, or galvanized marks are made on the exhaust system?
They cause a change in molecular 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 in 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 an exhaust system?
At welded or clamped areas and at the flanges
What is a common cause of turbocharger waste gate sticking?
Coke deposits or carbon buildup
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 engine’s performance and exhaust gas temperature change.
Name the components of a typical turbine exhaust nozzle.
The tail cone, exhaust ducts and support struts
What is the purpose of thrust reversers?
They help decelerate an aircraft after landing
How does a noise suppressor found on older turbojet engines work?
It converts low frequency sound, which is audible over great distance, to high frequency sound, thus reducing the sound footprint
What are the two most commonly used types of thrust reversers?
The clamshell and the cascade
How much thrust do the thrust reversers produce compared to the engine’s full forward thrust?
substantially less
What are the hazards of operating some thrust reversers at low ground speeds
Ingestion of foreign objects stirred up by the exhaust gases and reingestion of hot 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?
Controls the fuel/air mixture
What generally causes spark plug fouling?
Operating the engine with 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 high power settings, where the excess fuel aid in engine cooling. This system functions at throttle settings above cruise power settings
When the mixture is placed in the idle cutoff position, a slight rise in rpm is noted prior to the engine decelerating. What does this indicate?
The idle mixture is set correctly
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 fuel pump
What happens if the manual mixture control of a pressure injection carburetor is moved to the idle cutoff position?
The engine stops
How does an automatic mixture control function?
A sealed brass bellows connected to the fuel metering system expands and contracts with changes in pressure and temperature, adjusting the mixture accordingly.
What are some of the advantages of fuel injection systems over carburetor systems?
Less danger of induction icing, better acceleration, 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, compressor discharge pressure, burner pressure
What are the two major components of a supervisory electronics engine control?
The electronic control unit and the hydromechanical fuel control
What are some of the advantages of a full authority digital engine control over a hydromechanical fuel control?
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 more repeatable engine transients
What do turbine engine fuel spray nozzles do?
The inject fuel into the combustion chamber
What are the different engine indications used for trimming a turbine engine?
Either EPR or RPM is used depending on the engine
What maintenance adjustments are normally allowed on an installed hydromechanical fuel control?
Specific gravity for fuel, idle rpm, and max rpm
What type of pump can vary the amount of fuel discharged regardless of speed?
A 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 pump
What type of engine driven fuel pump is widely used other than gear or piston pumps?
A rotary vane type
What function do fuel boost pumps perform?
The 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 of concern?
Vapor lock is caused by insufficient fuel pressure, high fuel temperature and excessive fuel turbulence, which ma completely block any fuel flow resulting in engine failure
What function does the engine driven fuel pump on a turbine engine perform?
It provides a continuous 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 a shear section of the driveshaft in a dual element constant displacement pump?
If one element seizes, a portion of the driveshaft seizes, allowing the other element to continue to operate
Where in a turbine engine fuel system 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 tat 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 fuel 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?
A duplex fuel nozzle discharges two different spray patterns. The spray pattern is wider during start up and acceleration and narrows when engine speed increases above idle
What are the functions of pressurizing and dump portions of a pressurizing and dump valve?
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 manifold after engine shutdown
What purpose do fuel selector valves serve?
They allow tank and engine selection and provide a means for shutting off fuel flow
How can the remaining service life of a 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?
Both commutator and brushes should be inspected for wear beyond operational limits
Between field and armature windings in starter generators, which ordinarily receive current for operation in the start mode?
Generally both receive current for operation in start mode
What are possible sources of low pressure compressed air used for starting jet transport aircraft equipped with air turbine starters?
A GPU, an onboard APU, and compressed bleed air from an already running engine
When should ignition ideally occur?
A specific number of degrees before the piston reaches top dead center on the compression stroke
Why are dual magnetos used in the engine ignition system?
to improve combustion efficiency, and provide redundancy for safety.
Why is magneto timing so important?
For an engine to run properly, the spark plug in a cylinder has to fire at a specific time. To produce the required energy for the spark at the required time, the magneto must be in the E gap position, the breaker points must be starting to open, and the distributor must be electrically aligned with the correct cylinder.
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 magnet, soft iron core, and pole shoes. Distributor, etc
Name the three circuits of a high tension magneto system
Magnetic, primary, 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 field stress exists
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?
In the rotation cycle, when the magnetic rotor is in the E gap position, the primary points open, which interrupts the current flow in the primary circuit causing a high rate of flux change in the core, and inducing a pulse of high voltage in the secondary coil.
What is the P lead and how does it function?
The P lead connects the ignition switch to the primary circuit of the magneto. When the ignition switch is turned of, the P leads on both magnetos are grounded.
What is a 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 engine 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 cool down period.
What are the three main components of a turbine engine ignition system?
Ignition exciters, high tension leads, igniters
When the engine is operating, what does an ammeter indicate when connected to 1. Battery Positive Lead? 2. Generator Output Lead?
When connected to the battery positive 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?
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 umber of poles of an alternator determine?
The frequency of the alternator output
What are some of the methods used to maintain 400 Hz alternator output frequency on large turbojet or turbofan engines
CSD, IDG, VFG
Name the major parts of a DC motor
Armature, field, brushes, and frame assembly
Name the components of a direct cranking electric start system.
An electric motor, reduction gears, and an automatic engaging and disengaging mechanism
Name three types of DC motors
Series, shunt and compound
What type of DC motor is commonly used for a reciprocating engine starter and why?
Series is commonly used because it has a high starting torque under heavy load conditions
What are the operating modes of a turbine engine starter generator?
It operates first as a starter, then as a generator once the engine is running.
What is a possible indication wen a starter drags?
A dirty or worn starter commutator
Where would wire with high temperature insulation material 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?
AWG
How are wire sizes represented?
By a numbered gauge size. the smaller wires are represented by larger numbers
What is the maximum slack allowed between the supports of a single wire or bundle installation?
Not over 1/2 inch
Why are wires bonded on powerplant installations?
To provide a current return path for electrical accessories and to prevent static discharge.
A reciprocating engine is found to have excessive oil consumption without evidence of any oil leaks. What is likely the cause?
The piston rings are worn or broken
What are the functions of lubricating oil 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 heavy enough to provide proper oil film at engine operating temperatures.
What could happen to an oil that is too low in 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 are some of the factors that must be considered by an engine manufacturer in determining the proper of oil for a particular engine?
The operating load and temperature as well as the rotational speed.
Why do aircraft reciprocating engines use a relatively high viscosity oil?
Because they usually have large 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 ashless dispersant 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 of 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 the oil either through the cooler or around it in order to maintain proper operating oil temperatures.
What could be a possible indication if the oil cooler passage becomes obstructed?
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 type and size of the metal particles, this usually indicates abnormal wear and possible engine internal failure.
What should be done if metal particles are found in an engine oil filter?
Follow engine manufacturers maintenance instruction
Where is the most critical point of lubrication in a gas turbine engine?
At the turbine bearing
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 system?
At the oil pressure system, 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 in 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 cylinder heads of air cooled reciprocating engines. Airflow around the cooling fins transfers the heat from the cylinder heads to 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 augmenter cooling system work?
An outer tube placed over the exiting exhaust gas creates a venturi effect the draws more airflow over the engine, thus providing additional cooling.
Where should cowl flaps be positioned for ground operations?
Fully open
What type of power is used to operate cowl flaps?
Manual, hydraulic, electric
What should be done when cooling fin damage is discovered?
Depending on the scope of damage, some cooling fins may be repaired subject to the manufacturers overhaul and repair limitations. If an excessive amount of the 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 temperatures 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 and 25% for combustion. This air is used to cool the combustion chamber and the turbine.
In a turbine engine, where does bleed air come from that us used to cool bearings and other parts?
The engine compressor
What is the relationship between turbine engine upper 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?
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 types of fire detector systems are used for engine fire detection?
Overheat, rate of rise, and flame detectors (spot detectors)
How does a thermal switch fire protection system operate?
When heated past a predetermined temperature, the switch closes causing the warning devices in the cockpit to activate
How many thermal switches are needed in a thermal switch fire protection system?
at least 1
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 is required for this type of system to operate
What electrical power is required for a thermocouple fire protection system to operate?
Both the thermocouple produced power and the aircraft electrical power are required for this type of system to operate
What is the likely cause of a false fire warning?
The engine fire sensing loop is bent or kinked excessively
What are fire extinguishing systems designed to do?
They are designed to dilute the oxygen levels around the engine to a point that does not allow combustion, or to reduce temperatures below the ignition point.
Describe how a Kidde and Fenwal continuous loop fire detection system operate
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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 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 frangible disk, thereby releasing fire extinguishing agent
How is a fire extinguisher system with a high rate of discharge classified?
As an HRD fire extinguisher system
What do the red and yellow discs in a fire extinguishing system indicate?
A yellow disc indicates a normal discharge and a red disc indicates a thermal discharge
How is the fire extinguishing agent in an HRD system distributed, and how long does it take to discharge?
The agent is distributed through a series of high pressure tubes and takes one to two seconds to discharge.
What is the purpose of a pressure gauge in a fire extinguishing system?
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 propeller blades create thrust to pull or push an airplane through the air.
What is the difference between a fixed pitch propeller and a controllable pitch propeller?
A fixed pitch propeller is one that has a built in blade angle that cannot be changed by the pilot. These propellers can have the blade angle changed by the manufacturer or an approved repaid station to optimize performance. 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. Come controllable propellers also provide reverse pitch and feathering.
How are some wooden propeller 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 drive?
The blade angle increases to prevent an overspeed.
What are the functions of a constant speed propeller governor?
It boosts engine oil pressure before it enters the propeller hub, it senses rotational speed of the propeller, and the adjusts the oil flow to the propeller hub to change the pitch and therefore speed of the propeller
What is the purpose of propeller counterweights?
Centrifugal forces 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 speeder spring and flyweight forces are balanced.
How is a constant speed feathering propeller feathered?
By releasing the oil pressure in the governor, the counterweights and feathering spring move the propeller into feather. This happens automatically if the governor oil pressure drops to zero, or can be manually controlled by the pilot by moving the propeller control into the feathering detent.
What is an unfeathering accumulator?
It is an oil accumulator used to provide oil pressure to unfeather a propeller
What is alpha range and beta range and where are they found?
The alpha and beta ranges pertain to the operating modes of turboprop 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 propeller is operating in the zero or minimum thrust range and negative thrust or reverse thrust mode.
What systems are commonly used for propeller ice control?
Alcohol and electrical heat applied to the propeller blade root.
What propeller repairs can be preformed by a certified mechanic with a powerplant rating?
Only minor repairs and alterations can be performed by a certified mechanic with a powerplant rating. Major repairs must be performed by the manufacturer or a certified repair station. The propeller manufacturer’s maintenance manual outlines the scope of repairs.
How are wooden propellers generally cleaned?
With a brush or cloth and warm water with mild soap
Where would you find the correct method and technique for cleaning an aluminum propeller and hub?
The propeller manufacturers maintenance instruction
What type of nondestructive testing should be accomplished to a propeller after blending?
The procedures recommended by the manufacturer
What are the two criteria used by many manufacturers to determine the amount of bend damage that can be repaired by cold bending of aluminum propellers?
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 bladed propeller, what positions must the propeller be placed in when measurements are taken?
Vertical and Horizontal positions
What is a propeller protractor used for?
It is used to measure propeller blade angle
What blade conditions can cause engine vibration?
Vibration can be caused by propeller 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 position 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 hour inspections on aircraft engines?
Manufacturers maintenance manuals and FAR par 43 Appendix D
How do you identify the engine serial number?
It is on the engine data plate
Prior to returning a reciprocating engine to service after a 100 hr inspection, what operational checks must be performed?
Check the power output check magnetos, fuel and oil pressure check, cylinder and oil temperature check.
Where are life limited parts of an engine listed?
Engine maintenance manuals, TCDS, AWL section for continued airworthiness
Where can engine operating limits be found?
Engine manual, engine specification, TCDS, AMM
Why are hot section inspections performed on turbine engines?
To determine the integrity and wear of the hot section 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 temperature exceeds limitations?
A hot section inspection
Under what conditions is compliance with an engine service bulletin mandatory?
When an AD references the service bulletin or when compliance is part of the approved operating specifications for a commercial or air carrier operator. When engine or component overhaul procedures require compliance at time of overhaul.
What are the possible causes for a turbofan engine having high EGT, low RPM and high fuel flow at all EPR?
Turbine damage or loss of turbine efficiency due to wear.
