Powerplant Flashcards
1
Q
What is the purpose of dynamic dampeners on crankshafts?
A
Reduce vibration
2
Q
What type of bearings are found in recip engines?
A
-Plain bearings
-Ball bearings
-Roller bearings
3
Q
Are the connecting rods in each cylinder of radial engine the same?
A
No, radial engines use master and articulating rods.
4
Q
Name different piston rings:
A
-Oil control
-Compression
-Scraper rings.
5
Q
Where should piston ring gaps be installed relative to each other, and why?
A
Installed staggered to each other so that they do not align which prevents excessive blow-by
6
Q
What could result from incorrectly installed piston rings?
A
Excessive oil consumption
7
Q
What do oil control rings do?
A
Regulate the thickness of the oil film on the cylinder wall
8
Q
What is used to help prevent valve surge or floating in an aircraft?
A
Two or more springs are used on each valve.
9
Q
On engines equipped with hydraulic valve lifters, what should the running valve clearance be?
A
Zero
10
Q
What is the purpose of valve overlap?
A
-Better Volumetric efficiency
-Lowers cylinder operating temperature
11
Q
What indications are given in the event of a leaking or open primer while the engine is running?
A
The engine will not idle properly
12
Q
A cold cylinder is found when troubleshooting a running engine. What does this indicate?
A
No combustion in that cylinder.
13
Q
When pulling a prop through, a hissing sound is heard indicating valve blow-by. What procedure should be performed next?
A
Compression check.
14
Q
What is the purpose of performing a compression check?
A
Determine if the valves, pistons and rings are sealing properly.
15
Q
When an engine is overhauled, how is the total time affected? When an engine is rebuilt, how is its operating history affected?
A
The total time of the engine must be continued and the time since major overhaul is entered into the engine log. If the manufacture rebuilds the engine it can be granted ZERO time and is considered to have no previous operating history.
16
Q
What inspections should be performed after a prop strike without sudden stoppage?
A
-Inspect engine mounts, the crankcase, the nose section for damage
-Inspect the oil , oil filters screens for metal particles
-Inspect the crank or drive shaft for cracks and miss alignment
17
Q
Name some of the precautions that should be performed prior to engine removal:
A
- Disconnect battery
- Turn off fuel valves
- Chock the wheels
- If necessary install a tail stand
18
Q
When inspecting a piston, where are cracks most likely to be found?
A
-Base of the piston bosses
-Inside at the junction of the bore and the walls
-The ring lands
19
Q
What does it mean if an engine part is within “serviceable limits”
A
It means that the part is within the manufacturers limits
[DOES NOT REQUIRE REPLACEMENT]
20
Q
What tools or instruments are used to inspect a cylinder barrel for out-of-roundness?
A
A dial indicator or outside micrometer is usually used to measure the top of the cylinder at the skirt. A telescopic gauge can be used as well.
- 2 measurements must be taken 90* from each other.
21
Q
How can a loose stud in an engine crankcase be repaired?
A
Remove the stud and inspect the hole for size and thread condition. It may be necessary to use an oversize stud or heli-coil insert.
22
Q
What publication is used to check an engine for normal operation?
A
Manufacturers maintenance manual
23
Q
A weak cylinder is found during a compression check. What must be inspected?
A
The inside of the cylinder.
24
Q
What purpose does an oil analysis serve?
A
Metal particles in the oil show normal and abnormal wear of the engine. This helps in EVAL the engine’s internal condition.
25
What inspection should be performed on an engine that has been in storage?
Perform an inspection to determine if there is any corrosion damage.
26
Where would a carb air temp bulb be located?
In the RAM air intake duct.
27
What is the fuel pressure range on float-type carburetors?
3-5 PSI
28
Name the basic components of a fuel indicator system
The transmitter and the indicator
29
What unit of measure is generally used to indicate fuel flow?
Pounds or gallons per hour
30
Why is fuel flow monitored?
To determine fuel consumption and engine performance.
31
What does the manifold gauge indicate and how is it calibrated?
It measures absolute pressure in the engine and is calibrated in inches of mercury
32
What directly controls manifold pressure?
Throttle opening and engine rpm.
33
During engine operation, where should the prop control be set when checking manifold pressure?
-Low Pitch
-High RPM
34
Is the aircraft electrical system required to power a cylinder head temperature gauge?
No, a thermocouple is used as the electrical source.
35
What are the possible indications of an oil pressure transmitter or indicator malfunction?
A severe or sudden drop in oil pressure while temp and supply remain normal
36
What does a tachometer indicate on a recip engine?
Engine RPM
37
Where should the thermocouple be installed on a recip engine using a single probe cylinder head temperature system?
On the hottest cylinder.
38
Explain the main difference and advantage a turbofan over turbojet engines.
A turbofan uses a fan to bypass air around the engine core and provide thrust. The advantage is additional thrust at no extra fuel consumption
39
Name the major components in a gas turbine engine.
-Air inlet
-Compressor section
-Combustion section
-Turbine section
-Exhaust section
-Gearbox and
-Accessory section
40
What determines the amount of airflow through a turbine engine?
-Forward speed of the aircraft
-Compressor speed
-Air density
41
Name the two types of compressors commonly used in turbine engines?
-Axial
-Centrifugal flow
compressors
42
Name two different methods for attaching turbine engine rotor blades to the rotor disks?
-Dovetail type root
-Bulb type root
-Fir tree type root
43
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 the other.
44
What are the different types of combustion chambers used in turbine engines?
-Can
-Annular
-Can-annular
-Reverse flow annular
45
What prevents the combustion chambers from burning?
Cooling air along the inside of the liner
46
What is the purpose of interconnecting tubes attached between can-type combustion chambers?
For flame propagation during start
47
What functions do axial flow turbine nozzles perform?
They direct the mass airflow to drive the turbine rotor at a specific angle
48
How is thermal stress relieved on a turbine disc?
By directing bleed air onto the face of the disk, or by grooves being cut in the disk.
49
What are carbon seals used for in turbine engines?
They are used as oil seals for the rotor shaft bearings.
50
What is shaft horsepower?
It is an indication of the torque developed by a turboprop or turboshaft engine.
51
What is the purpose of an APU?
They provide ground electrical and pneumatic power for aircraft systems when the engines are not running. Pneumatic power can be used for engine starting, ground heating or air conditioning, and anti-icing. Many APUs may also be used as an emergency source of in flight electrical power.
52
Name the main components of a typical APU?
-A small power turbine for power and bleed air
-Electrical generator
53
What is the greatest demand placed on an APU?
When supplying bleed air.
54
How is an APU generally started?
With its own electrical starter and battery power
55
Where does the APU get its fuel supply?
From one of the aircrafts main fuel tanks.
56
At what speed does a gas turbine APU operate and how is this speed maintained?
At or near its rated speed regardless and is maintained by its fuel flow
57
What is used to prevent a heavily loaded APU from exceeding its maximum EGT?
A LOAD CONTROL VALVE modulates the pneumatic load to maintain EGT's within limits.
58
How is an APU shut down and why is the procedure used?
-Unload APU by closing the bleed air valve,
-It is run for a specified amount of time to allow the EGT to cool and stabilize.
If a heavily loaded APU is abruptly shut down without any cool down period, damage could occur as a result of thermal shock.
59
What powers the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?
Fuel pressure
60
What is fan blade slinging?
Overlapping of the midspan shrouds of the fan blade.
61
When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?
Any rubbing or other unusual sounds from the engine.
62
Why are compressor washes performed and what methods are commonly used?
To remove any contaminants from the compressor section and improve engine performance.
-Fluid wash
-Abrasive grit wash
63
How can you tell if a turbofan or turbojet engine is out of trim?
High EGT at target EPR for takeoff
64
Name the different types of compressor blade damage that may be found during inspection.
-Dents
-Cracks
-Galling
-Pitting
-Scratches
-Burrs
-Burns
-Gouges
65
What kind of markers can be used to mark the parts in hot and cold sections during repair?
-Layout dye
-Felt tip marker
-Chalk.
66
How does relative humidity affect turbine engine?
Negligible effect.
67
What criteria determines the replacement life limited turbine engine components?
-Cycles
-Hours
-Calendar time
68
If turbine blades are removed from a turbine disc, why should they be re-installed in the same location?
To maintain balance of the turbine wheel.
69
How are gas turbine engine tachometers calibrated?
Percentage of RPM
70
On a turbine engine, what is the engine pressure ratio and what does it indicate?
EPR = ratio of intake pressure to turbine exhaust pressure
****Indicates thrust developed****
71
On a turbine engine, what does exhaust gas temperature indicate and how is it obtained?
EGT is the average temp of the turbine discharge gasses
[Obtained by thermocouples near the turbine exit.]
72
Can the EGT system of a turbine engine be checked without running the engine?
Yes by checking the resistance of the thermocouples and circuits.
73
Name three components on the induction system of a recip engine:
-Air scoop,
-Carburetor
-Intake manifold
74
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.
[BAD FILTER]
75
How does induction icing affect engine performance?
It causes a reduction in power and possible erratic operation.
76
How is induction icing categorized?
-Impact ice
-Fuel evaporation ice
-Throttle ice
77
What is common method used to prevent induction system ice in recip engine?
Preheating the induction air
78
What causes fuel evaporation ice?
When fuel evaporates into the airstream it decreases air temperature resulting in fuel evap ice.
79
Is carburetor ice more likely to occur at a higher or lower power setting and why?
At lower power setting because the throttle is partly closed, offering a larger surface area for the ice to accumulate.
80
What may be the indication of leaking intake pipes?
The engine runs rough at low RPM.
81
What happens to engine power when the carb heat is applied?
Noticeable drop in power.
82
What could happen if carb heat is applied at high power settings?
Detonation
83
What are two types of supercharged induction systems?
-Internally driven
-Externally driven
84
How and at what point does an internally driven supercharger boost air pressure?
An engine driven impeller compresses the fuel air mixture after it leaves the carburetor.
85
What is used to power a turbocharger?
Exhaust gas directed onto the turbocharger turbine.
86
What could result if the wastegate on a turbocharger system does not fully close?
-Can't produce its rated power at certain altitudes
-Aircraft struggles to or can't reach critical altitude.
87
What function does a turbocharger waste gate perform?
It controls the amount of exhaust gas either into or around the turbocharger thus controlling boost pressure of the turbocharger.
88
What could cause a turbocharged engine to surge?
Waste gate or controller malfunction.
89
What are the most common ways to control a waste gate?
-Either mechanically with linkages to the throttle or a separate control
-Actuator that is driven by oil pressure
90
In a pressurized recip aircraft, what component in the turbocharger system is used to limit the amount of turbocharger airflow used for cabin pressurization?
The sonic venturi
91
What is the function of a divergent shaped jet inlet during subsonic flight?
It causes the air velocity to decrease with a subsequent increase in air pressure.
92
Where are bellmouth inlet ducts typically found?
Helicopter engines
93
How do venturi type particle separators found on turbine powered helicopters function?
The intake is curved and the debris gains too much inertia to allow it to follow the curved intake toward the engine and is channeled away from the compressor.
94
What are the most common methods used for anti-icing of turbine engine inlet ducts?
-Bleed air
-Electric heating elements
95
What is the purpose of the exhaust system?
To remove high temp noxious gases
96
Name two types of recip engine exhaust systems?
-Short stack
-Collector system
97
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 back pressure.
98
What could result if the internal baffles or diffusers in an exhaust system fail?
Restricted flow of exhaust gases resulting in a loss of engine power.
99
What type of exhaust system is used on turbocharged engines?
The collector system
100
What kind of material is normally used to make the muffler shrouds found in the exhaust system?
Stainless steel
101
How do you inspect the internal baffles and diffusers of an exhaust system?
By disassembling the exhaust system as necessary and visually inspecting the components.
102
Why is an exhaust system failure considered a severe hazard?
-Carbon monoxide poisoning
-Loss of engine power
-Fire
103
What could happen if lead, zinc, or galvanized marks are made on an exhaust system?
Change molecular structure,
result in cracks when heated
104
What happens if the heat exchanger leaks exhaust gasses into the induction system?
Loss of engine power.
105
What is an indication of an exhaust leak?
Sooty black deposit in the area of the leak.
106
Where are the most common places to find cracks in the exhaust system?
-Welded areas
-Clamped areas
-At the flanges
107
What is a common cause of turbocharger waste gate sticking?
-Coke deposits [Excessive carbon build up]
-Carbon build up
108
Why are turbocharged exhaust system leaks very damaging at high altitudes?
Pressure differential will cause the leak to escape with torch like intensity
109
What are exhaust system coke deposits?
Excessive carbon buildup.
110
What is the result of changing the exhaust nozzle area of a turbine engine?
-Engine performance change
-EGT changes
111
Name the components of a typical turbine exhaust nozzle?
-Tail cone
-Exhaust ducts
-Support struts
112
What is the purpose of thrust reversers?
Assist deceleration of aircraft on landing
113
How does a noise suppressor found on older turbojet engines work?
It converts low frequency into high frequency thus reducing the sound footprint.
114
What are the two most commonly used types of thrust reverses?
-Aerodynamic blockage
-Mechanical blockage
115
How much thrust do thrust reverses produce compared to the engines full forward thrust?
Substantially less
116
What are the hazards of operating some thrust reverses at low ground speeds?
-Ingest foreign objects stirred up by the exhaust gasses
-Re-ingest hot exhaust gasses.
117
What are some of the sources used to heat the fuel in a turbine engine fuel system?
-Bleed air
-Engine oil
118
What are the most common types of fuel metering systems used on small recip engines?
-Float type carb
-Pressure injection
-Direct injection
119
What function does the mixture control perform?
Controls the fuel/air mixture ratio
120
What generally causes spark plug fouling?
Running the engine excessively rich at idle
121
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.
122
What is the carb economizer system?
Power enrichment system provides richer mixture at higher power settings, the extra fuel aids in engine cooling.
123
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.
124
Why should engine rpm be accelerated periodically when making carburetor adjustments?
Clear the engine
125
What happens if the manual mixture control of a pressure injection carb is moved to the idle cutoff position?
The engine stops.
126
What maintains the fuel pressure in a pressure injection carb?
Engine driven fuel pump
127
How does an automatic mixture control function?
Sealed brass bellows expand and contract w/ changes in pressure & temperature to adjust the mixture accordingly.
128
What are some of the advantages of fuel injection systems over carb systems?
-Less danger of induction icing
-Better acceleration
-Better fuel distribution
-Better fuel economy
-Reduced overheating of individual cylinders.
129
What purpose do turbine engine fuel control units serve?
Automatically meter fuel to the engine.
130
What are the two basic types of turbine engine fuel control units?
-Hydromechanical
-Electrical
131
What are the engine variables detected by the fuel control?
-Power lever position
-Engine rpm
-Compressor inlet temp
-Compressor inlet pressure
-Compressor discharge pressure
-Burner pressure.
132
What are the two major components of a supervisory electronics engine control?
The ECU and the hydromechanical fuel control.
133
What are some of the advantages of a full authority digital engine control [FADEC] over a hydromechanical fuel control?
-Better fuel economy
-Improved starts
-No engine trimming
-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.
134
What do turbine engine fuel spray nozzles do?
Inject fuel into the combustion area.
135
What are the different engine indications used for trimming a turbine engine?
EPR or RPM is used depending on the engine.
136
What maintenance adjustments are normally allowed on an installed hydromechanical fuel controller?
-Specific gravity for fuel
-Idle RPM
-Max RPM.
137
What type of pump can vary the amount of fuel discharged regardless of speed?
A variable displacement pump
138
What is used to keep water, sediment, and foreign matter out of the carburetor?
Main fuel strainer.
139
What is the purpose of a pressure relief valve in a constant displacement pump?
It returns excess fuel that is not required to the inlet side of the pump.
140
What type of engine driven fuel pump is widely used other than gear or piston pumps?
A rotary vane type.
141
What function do fuel boost pumps perform?
They supply pressurized fuel to the fuel pump, which helps prevent vapor lock and cavitation.
142
What is a commonly used type of fuel boost pump?
The centrifugal type.
143
What causes vapor lock and why is it a concern?
-Insufficient fuel pressure
-High fuel temperature
-Excessive fuel turbulence
-It can block fuel flow to the engine resulting in failure.
144
What function does an engine driven pump on a turbine engine perform?
Continuous supply of fuel at the proper pressure while the engine is running.
145
Name the two categories of turbine engine pumps.
-Constant displacement
-Variable displacement
146
What category is a gear type pump classified in?
Constant displacement.
147
When performing an external inspection of an engine driven fuel pump, what should you look for?
Leaks and security of mounting.
148
What is the purpose of a shear section of the driveshaft in a dual element constant displacement pump?
Even if one element seizes the other still operates
149
Where in a turbine engine fuel system is ice formation likely to occur and how is it prevented?
At the fuel filter, and it is prevented by fuel heater or fuel additive.
150
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.
151
What is the purpose of duplex nozzle?
Duplex nozzle discharges two different spray patterns, one wider during startup and acceleration and narrows when engine speed increases above idle.
152
What are the functions of the pressurizing and dump portions of pressurizing and dump valve?
-Pressurizing portion provides primary and secondary fuel flow to duplex nozzles
-Dump portion allows fuel to drain from the manifolds after engine shutdown.
153
What purpose do fuel selector valves serve?
They allow tank and engine selection and provide a means for shutting off fuel flow.
154
How can the remaining service life of starter-generator brushes be determined?
By visually inspecting the amount of wear groove remaining on the brushes.
155
What components of the starter-generator require periodic inspection?
Both commutator and brushes
156
Between field and armature windings in starter-generators, which ordinarily receive current for operation in the start mode?
BOTH field and armature
157
What are possible sources of low pressure compressed air used for starting jet transport aircraft equipped with air turbine starters?
-Ground power unit
-On board APU
-Compressed bleed air form an already running engine.
158
When should ignition ideally occur?
Specific number of degrees before the piston reaches TDC on the compression stroke.
159
Why are dual mags used in the engine ignition system?
Improve combustion efficiency and provide redundancy for safety.
160
Why is mag timing so important?
For the 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 or engine wont run or will run rough
161
What function does a magneto perform?
It produces a high voltage that forces a spark to arc across a spark plug gap.
162
Name the components of a high tension mag system
-Permanent rotating magnet
-Soft iron core
-Pole shoes.
163
Name the three main circuits of a high tension mag system.
-Magnetic
-Primary
-Secondary
164
What is an E-gap angle?
Where maximum magnetic field stress exists and is few degrees beyond the neutral position of a rotating magnet
165
What reduces arcing in the points and also aids the collapsing of the magnetic field in a magneto?
A capacitor.
166
How does a magneto produce the high voltage spark required to fire a spark plug?
In the rotation cycle, when the magnetic rotor is in e gap 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.
167
What is the P-lead and how does it function?
The P-lead connects the ignition switch to the primary circuit of the magneto.
OFF = both grounded
BOTH = both on
LEFT = Right grounded
Right = left grounded
168
What is the magneto timing light used for and what does it indicate?
Used for mag timing and indicates exact instant the mag points open.
169
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.
170
What is the function of a duty cycle in relation to a turbine engine ignition system?
Allows operation of the ignition system for a X amount of time, then followed by a minimum specified cooling down period.
171
What are the three main components of a turbine engine ignition system?
-Ignition exciters
-High tension leads
-Igniters
172
When the engine is operating, what does an ammeter / loadmeter indicate when connected to: 1. Battery positive lead, 2. Generator output lead?
1. Ammeter indicates whether the battery is charging or discharging,
2. indicates the current produced by the generator or electrical system load.
173
What is done to ensure each generator shares the same load?
The generators are paralleled
174
Where would you find generator rating and performance data?
On the data plate attached to the generator.
175
How is the voltage of a DC generator controlled?
By varrying the field current strength.
176
What is the most common type of alternator used in most aircraft AC systems?
Three phase alternator.
177
How does a voltage regulator control the voltage of an alternator?
By regulating the voltage output of the DC exciter.
178
What does the speed of rotation and number of poles of an alternator determine?
The frequency of the alternator output
179
What are some of the methods used to maintain 400 Hz alternator output frequency on large turbojet turbofan engines?
-Constant speed drives
-Integrated drive generators
-Variable speed constant frequency power systems.
180
Name the major parts of a DC motor?
-The armature
-Field
-Brushes
-Frame assembly
181
Name the components of a direct cranking electric starter system:
-Electric motor
-Reduction gears
-Automatic engaging/disengaging mechanism.
182
Name three types of DC motors:
-Series
-Shunt
-Compound
183
What type of DC motor is commonly used for a reciprocating engine starter and why?
A series wound motor because it has high starting torque under heavy load conditions.
184
What are the operating modes of a turbine engine starter motor?
It operates first as the starter, then as the generator when the engine is running.
185
What is possible indication when a starter drags?
A dirty or worn starter commutator.
186
Where would wire with high temp insulation be used?
When they run close to high temp areas such as exhaust stacks or heating ducts.
187
What is the size standard for electrical wire used in US manufactured aircraft?
AWG American wire gauge
188
How are wire sizes represented?
By a numbered gauge size. The smaller wires are represented by larger numbers. big wires are small numbers.
189
What is the maximum slack allowed between the supports of a single wire or bundle instillation?
Not over 1/2 inch
190
Why are wires bonded on powerplant installations?
To provide a current return path for electrical accessories, and to prevent static discharge.
191
A recip engine is found to have excessive oil consumption without evidence of any leaks. What is the likely cause?
Piston rings are worn or broken
192
What are the functions of lubing oil in recip engines?
Reduce the friction between moving parts and remove heat.
193
Name two important characteristics of aircraft engine oil:
-Oil must be light enough to circulate
-Heavy enough to provide proper oil film at operating temps.
194
What could happen to an oil that is too low in viscosity at normal engine operating temperatures?
It may become too thin that the oil film between moving parts is easily broken, resulting in premature wear.
195
What are some of the factors that must be considered by an engine manufacturer in determining the proper grade of oil for a particular engine?
-Operating load
-Operating temp
-Rotational speed
196
Why do aircraft recip engines use a relatively high viscosity oil?
Because they have large operating clearances and operate at high temps and pressures.
197
Name some oil contaminants:
-Dirt
-Metal particles
-Carbon
-Moisture
-Acids.
198
What is a possible indication of low oil pressure together with high oil temperature?
A low supply of oil.
199
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.
200
Why do oil reservoirs have expansion space?
-Oil foaming
-Thermal expansion
-Air in the return oil.
201
What could cause oil foaming?
-Diluted oil
-Contaminated oil
-Oil level being too high.
202
What controls oil pressure in a gear type oil pressure pump?
Oil pressure relief valve
203
What function does an oil cooler bypass valve perform?
It directs the oil through a cooler or around it in order to maintain proper operating temps.
204
Where is the oil temp bulb usually located?
At the engine oil inlet.
205
What does the presence of metal particles in an engine oil filter indicate?
Depending on the size of the particles this usually indicates abnormal wear and possible engine internal failure.
206
What should be done if metal particles are found in an engine oil filter?
Follow engine manufacturers instruction
207
Where is the most critical point of lube in a gas turbine engine?
At the turbine bearing.
208
What type of oil is used in a turbine engine oil system?
Synthetic oil.
209
Where are oil screens or filters most likely located in a turbine engine oil system?
-Main filter
-Scavenge system
-At or just before the oil jet
210
Name two types of turbine engine oil coolers?
-Air cooled
-Fuel cooled
211
What could happen to an oil that is too low viscosity at normal engine op temperatures?
It may become so thin that the oil between moving parts is easily broken resulting in premature wear.
212
What effect does excessive heat have on recip engines?
It shortens the life of engine parts, changes the behavior of combustion, and impairs lubrication.
213
What is the purpose of cooling fins?
Provide a larger cooling surface area for removing heat from the cylinder heads of air cooled recip engines.
214
What are the reasons for using engine cowlings, baffles and cowl air seals?
-Streamline the engine area to reduce drag
-Direct airflow for cooling.
215
How does an augmented cooling system work?
Outer tube placed over the exiting exhaust gas creates a venturi effect that draws more airflow over the engine for cooling.
216
Where should cowl flaps be positioned for ground operations?
Fully open
217
What type of power is used to operate cowl flaps?
-Manual
-Hydraulic
-Electrical
218
What should be done when cooling fin damage is discovered?
Sometimes they can be repaired subject to manufacturers repair and overhaul manual, if too much fin is broken off then the cylinder must be replaced.
219
Why is cowl flap adjustment important?
The movement must be within tolerance to keep cylinder head temperatures within allowable limits.
220
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 only about 25% for combustion. This air is used to cool the combustion chamber and turbine.
221
In a turbine engine, where does bleed air come from that is used to cool bearings and other parts?
The engine compressor
222
What is the relationship between turbine engine temperature limits and power produced?
The higher the combustion temp that the engine can withstand without damage, the more power it can make.
223
What is the approx percentage of air passing through a turbine that is used for cooling rather than combustion?
75%
224
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 turbine inlet guide vanes and first stage rotor blades can lower temps enough to prevent heat damage.
225
What types of fire detector systems are used for engine fire detection?
-Overheat
-Rate of rise
-Flame detectors
226
How does a thermal switch fire protection system operate?
When heated past a predetermined temperature, the switch closes causing a warning device in the cockpit to activate.
227
How many thermal switches are needed in a thermal switch fire protection system?
At least one
228
What kind of fire detection system allows more complete coverage than a spot type system?
Continuous loop system
229
What happens if an engine equipped with a thermocouple fire warning system overheats slowly?
Nothing because fast temp rise is required for this type of system to operate
230
What is likely to cause a false fire warning?
The engine fire sensing loop is bent or kinked excessively.
231
What are fire extinguishing systems designed to do?
They are designed to dilute the O2 levels around the engine to a point that does not allow combustion or to reduce temperatures below the ignition point.
232
Describe how a kidde and fenwal continuous loop fire detection system functions?
-When a fire occurs in kidde system the resistance of the thermistor material drops allowing current to flow between the two wires and activate an alarm.
-With the fenwal system, the core resistance of the beads drop allowing current to flow between the electrode and ground energizing the alarm system.
233
What elements must be present for a fire to occur?
-Ignition source such as heat or a spark
-Fuel
-Oxygen.
234
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 CFG may still be used and are subject to strict handling and disposal regulations.
235
How are fire extinguishing agents distributed?
Through perforated tubing and discharge nozzles.
236
What is the purpose of the discharge cartridge and how is it activated?
Electrically ignited, fires a projectile into the frangible disk, thereby releasing fire extinguishing agents.
237
How is a fire extinguisher system with a high rate of discharge classified?
Spray nozzles and perforated tubing
As a HRD fire extinguisher system.
238
What do the red and yellow discs in a fire extinguishing system indicate?
A yellow disc means it was discharged normally, a red disc indicates thermal discharge.
239
How is the fire extinguishing agent in an HRD system distributed, and how long does it take to discharge?
Through a series of high pressure tubes and takes one to two seconds to discharge.
240
What is the purpose of a pressure gauge in a fire extinguishing system?
Indicates the pressure within the container, to check if the pressure is within limits. A pressure-temp chart is used.
241
What is the function of a propeller?
Create thrust to pull or push airplane through the air.
242
What is the difference between a fixed pitch prop and a controllable pitch prop?
Fixed pitch propellers blade angle cannot be changed by the pilot where as controllable pitch props blade angles may be changed by the pilot.
243
How are some wooden prop blades protected from wear?
By metal tipping fastened to the leading edge and tip.
244
What happens to the blade angle of a constant speed prop during a constant power dive?
The angle increases to prevent an overspeed.
245
What are the functions of a constant speed prop governor?
-Boosts oil pressure before it enters the hub
-Senses prop rotation speed
-Adjusts the oil flow to the prop to change pitch and prop speed
246
What is the purpose for prop counterweights?
Centrifugal force acting on the counterweights causes the blade angle to increase.
247
What is meant when a propeller governor is in an on-speed condition?
-Governor doesn't have to accelerate or decelerate speeder ring
-Flyweight forces are in balance
248
How is a constant speed feathering propeller feathered?
When the governor releases oil pressure the counterweights and feathering spring move the prop into feather position.
249
What is an unfeathering accumulator?
Oil accumulator used to provide oil pressure to unfeather a prop.
250
What is alpha range and beta range and where are they found?
Alpha is for operation in standard constant speed mode which is usually in flight, and beta is for ground operation when the prop is in zero or min thrust range and negative thrust or reverse thrust mode.
251
What systems are commonly used for prop ice control?
Fluid [ALCOHOL] and electrical heat applied to the prop blade root.
252
What prop repairs can be performed by a certified mechanic with a Powerplant rating?
Only minor repairs and alterations
253
How are wooden props cleaned?
With a brush or cloth and warm water and mild soap.
254
Where would you find the correct method and technique for cleaning an aluminum prop and hub?
In the prop manufacturers maintenance instructions.
255
What type of nondestructive testing should be accomplished to a prop after blending?
Whichever procedure recommended by the manufacturer.
256
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.
257
How can repair file marks be removed from an aluminum prop?
With very fine sand paper
258
When performing a static balance on a two bladed prop what positions must the prop be placed in when measurements are taken?
Vertical and horizontal positions
259
What is a prop protractor used for?
To measure prop blade angle
260
What blade conditions can cause engine vibration?
-Prop out of track
-Prop out of balance
-Incorrect blade angle setting.
261
What is blade tracking?
Comparing the position of the prop blade tips relative to each other.
262
What controls both manifold pressure and RPM of an engine with a fixed pitch prop?
The throttle
263
What publications can be used as a guide for 100 hour inspections on aircraft engines?
-Manufacturers maintenance manual
-FAR part 43 appendix D
264
How do you identify the engine serial number?
On the data plate
265
Prior to returning a recip engine to service after a 100 hour inspection what operational checks must be performed?
-Check the power output
-Magnetos
-Fuel pressure
-Oil pressure
-Cylinder temp
-Oil temp
266
Where are life limits parts of an engine listed?
-In the maintenance manual
-TCDS
-Airworthiness limitation section of the instructions for continued airworthiness.
267
Where can engine limitations be found?
-In the engine manual
-TCDS
-Aircraft maintenance manual.
268
Why are hot section inspections performed on turbine engines?
To determine the integrity and wear of the hot section components.
269
What inspections can be performed following a turbine engine overspeed?
Refer to the engine manufacturer maintenance manual for the required procedures.
270
What inspection must be performed on a turbine engine if the exhaust gas temp exceeds limitation?
Hot section inspection
271
What FAA approvals are required when installing an engine that is not on the TCDS
An STC
272
Under what conditions is compliance with an engine service bulletin mandatory?
When the airworthiness directive references the SB or when the compliance part of the approved operating specs for a commercial or air carrier operator. Or when the overhaul procedure require compliance at the time of overhaul.
273
What are the possible causes for a turbojet or fan engine having high EGT low RPM and high fuel flow at all engine pressure ratios?
Turbine damage or loss of efficiency due to wear.
