POWERPLANT Flashcards
(186 cards)
1
Q
What procedure should be followed when valve blow-by is indicated by a hissing sound on a reciprocating engine when pulling the propeller through?
A
Perform a cylinder compression test to identify the faulty cylinder.
2
Q
What is the running valve clearance on engines with hydraulic valve lifters?
A
Zero
3
Q
What does a cold cylinder indicate when troubleshooting a running engine malfunction?
A
Lack of combustion in that cylinder.
4
Q
What factors about the condition of an engine can be learned by studying the results of a compression test?
A
The results of a compression test determine if the valves, piston rings, and pistons are adequately sealed.
5
Q
What should be done to repair a loose stud in an engine crankcase?
A
Remove the loose stud and inspect the hole for size and the condition of the threads. A suitable oversized stud may be necessary.
6
Q
How is a cylinder barrel inspected for out-of-roundness?
A
A cylinder bore gauge (or a telescopic gauge and micrometer, or an inside micrometer) can be used to measure at the top of the cylinder and also at the skirt. Two readings should be taken, 90° from each other.
7
Q
What types of connecting rods are commonly found in radial engines?
A
Master and articulated rod assemblies.
8
Q
What are the different types of piston rings?
A
Compression, oil control, and oil scraper.
9
Q
What is the purpose of oil control rings?
A
Oil control rings regulate the thickness of the oil film on the cylinder wall.
10
Q
What types of bearings are generally used in reciprocating engines?
A
Plain, ball, and roller.
11
Q
How are piston ring gaps installed relative to each other on a piston, and why?
A
Compression ring gaps should be installed in staggered positions (not aligned) around the piston to prevent excessive blow-by.
12
Q
What is the purpose of valve overlap?
A
It permits better volumetric efficiency and lowers the cylinder operating temperature.
13
Q
What is the purpose of crankshaft dynamic dampers?
A
To reduce engine vibration.
14
Q
What is meant when it is said that an engine part is within serviceable limits?
A
A part that is within serviceable limits will not likely wear to the point of causing engine failure within the next time between overhaul (TBO) intervals.
15
Q
Name at least one part of an inspection that should be made after a propeller strike (not sudden stoppage).
A
Inspect the propeller drive shaft or crankshaft for misalignment.
16
Q
What is an indication that a primer is leaking or is open during engine operation?
A
The engine will not idle properly.
17
Q
What may be the result of the incorrect installation of piston rings?
A
Excessive oil consumption.
18
Q
What are some indications of an induction system?
A
Low power and uneven running.
19
Q
When an engine is rebuilt by the manufacturer, how is its operating history affected?
A
A rebuilt engine is considered to have no previous operating history and can therefore be issued a zero-time record.
20
Q
What is used in an aircraft engine to help prevent valve surge or float from occurring?
A
Two or more springs on each valve.
21
Q
What are the major components of a typical gas turbine engine?
A
An air inlet, compressor section, combustion section, turbine section, exhaust section, and accessory section.
22
Q
What determines the amount of air passing through a turbine engine?
A
Compressor speed, forward speed of the aircraft, and air density.
23
Q
What are the two principal types of compressors currently used in turbine engines?
A
Centrifugal and axial flow.
24
Q
How are turbine engine rotor blades attached to rotor disks? (Name at least two methods.)
A
Bulb-type root and Fir tree-type root.
25
Name at least three types of combustion chamber systems.
Can, Annular, and Can-annular.
26
What is the purpose of the interconnect tubes attached between can-type combustion chambers?
For flame propagation during starting.
27
What prevents the burning of combustion chambers?
Cooling air along the inside of the liner.
28
What are carbon seals used for in turbine engines?
As oil seals for the rotor shaft bearings.
29
What are the desired effects of turbine engine compressor field cleaning?
Removal of contaminant deposits from interior engine surfaces and improved engine performance.
30
What is the main operating difference between turbofan and turbojet engines?
The air that flows through the fan section of a turbofan engine bypasses, or flows around, the outside of the core engine instead of through it.
31
What methods are commonly used to accomplish turbine engine compressor field cleaning?
Fluid wash and abrasive grit blast.
32
Name an advantage of a turbofan over a turbojet.
Additional thrust without increasing fuel flow.
33
What are the functions of axial flow turbine nozzles?
They prepare the mass airflow for driving the turbine rotor and deflect the gases to a specific angle.
34
What are some ways of relieving thermal stress on a turbine disk?
By directing bleed air onto the face of the disk, or by grooving in the turbine disk.
35
What type of compressor blade damage may be found when inspecting compressor blades?
Dents, galling, pitting, cracks, scratches, burrs, burns, and gouges.
36
What is used to mark both hot and cold section parts for repair?
Layout dye, commercial felt-tip marker, or chalk.
37
What is the effect of relative humidity on turbojet or turbofan power?
Negligible.
38
What may be the indications if a turbojet or turbofan engine is out of trim?
The engine has a high exhaust gas temperature at the target engine pressure ratio for takeoff power.
39
What would be the possible cause for a turbojet or turbofan engine having high exhaust gas temperature, low RPM, and high fuel consumption at all engine pressure ratio settings?
Possible turbine damage or loss of turbine efficiency.
40
What are the basic components of an engine fuel flow system?
A transmitter and an indicator.
41
What type of readout is indicated on a fuel flow system?
The amount of fuel flow in pounds or gallons per hour.
42
What is the reason for monitoring fuel flow?
Fuel flow is an indication of fuel consumption and engine performance.
43
What does a manifold pressure gauge indicate?
Absolute manifold pressure in inches of mercury.
44
What directly controls manifold pressure?
Engine RPM and throttle opening.
45
On an engine equipped with a fixed-pitch propeller, what controls both manifold pressure and engine RPM?
The throttle control.
46
What does a reciprocating engine tachometer indicate?
Engine crankshaft speed.
47
What are turbine engine tachometer gauges designed to indicate?
Percentage of compressor RPM.
48
What does turbine engine exhaust gas temperature (EGT) indicate?
It is the average temperature of turbine discharge gases.
49
How is turbine engine EGT obtained?
Usually, several thermocouples are spaced at intervals around the exhaust duct perimeter near the turbine exit.
50
What does the turbine engine pressure ratio indicate?
Thrust is being developed by the engine.
51
What pressures are measured in the engine pressure ratio?
Total inlet pressure and total turbine exhaust pressure.
52
What is the torque being developed by a turboprop engine an indication of?
Shaft horsepower.
53
Where should the thermocouple be installed on a single-probe cylinder head temperature system?
On the hottest cylinder.
54
What is the electrical source for a cylinder head temperature system?
A thermocouple.
55
Where is the location of the carburetor air temperature bulb?
It is located in the ram air intake duct.
56
What is the possible cause when a turboprop engine oil pressure drops off severely, and the oil supply remains?
Oil pressure transmitter or indicator malfunction.
57
How can a turbine engine EGT system be checked without running the engine?
By checking the resistance of thermocouples and circuits.
58
When checking the manifold pressure during engine operation, in what position would the prop control be set?
Low pitch.
59
Name at least two types of fire detector systems used for engine fire protection.
Overheat and Rate of temperature rise.
60
What will happen in a thermocouple fire warning system on an engine that overheats slowly?
Nothing, because it takes a fast rate of rise or rapid heating to operate.
61
What happens to a thermal switch fire protection system when it is heated enough to operate?
Switch contacts close and provide a ground for the cockpit fire warning devices.
62
What electrical power is needed for a thermocouple fire protection system?
The aircraft's electrical system and thermocouple produced voltage.
63
What is the minimum number of thermal switch units needed for a thermal switch fire protection system?
At least one.
64
What is a type of fire detection system that permits more complete coverage of an area than spot-type temperature detectors?
A continuous loop system.
65
What is the principle of operation of a Kidde continuous loop fire protection system?
Two wires are embedded in a special ceramic core within an Inconel tube. One wire is a ground, and the second wire is a hot lead that provides a current when the ceramic core material changes its resistance due to temperature.
66
What is the principle of operation in a Fenwal continuous loop fire protection system?
In an Inconel tube, a single lowered nickel wire is surrounded by eutectic salt. The resistance sharply decreases with temperature rise.
67
What is the purpose of a fire extinguishing system?
To dilute the atmosphere around a fire with an inert agent that will not support combustion.
68
What are two methods used to distribute fire extinguishing agents?
Perforated tubing and/or discharge nozzles.
69
What is an HRD fire extinguisher system?
A fire extinguisher system with a high rate of discharge.
70
How is an HRD fire extinguisher agent distributed?
Open-ended tubes.
71
How long does it take to discharge an HRD agent?
One to two seconds.
72
What group of fire extinguishing agents are no longer being manufactured because of environmental concerns and are subject to strict handling and disposal regulations?
Halons (or Freon or chlorofluorocarbons [CFCs]).
73
What are the essential ingredients necessary for any fire to occur?
Heat (or ignition source), fuel, and oxygen.
74
What is the purpose of a discharge cartridge, and how is it activated?
The electrically operated discharge cartridge releases the fire extinguishing agent.
75
What are the red and yellow disks associated with a fire extinguisher system used to indicate?
Red indicates a thermal discharge, and yellow indicates a normal discharge.
76
What is likely to happen when an engine fire-sensing loop is excessively kinked or bent?
A false fire warning.
77
What indicates low agent pressure in a container in a fire extinguisher system?
A pressure gauge.
78
What is the proper method for determining the fire extinguisher container pressure?
The container gauge pressure used with a pressure-temperature curve/chart will indicate if the pressure is within limits.
79
Where are generator rating and performance data located?
They are stamped on a nameplate attached to the generator.
80
What does an ammeter/load meter indicate when it is connected to the battery positive lead, and the engine is operating?
Whether the generator is supplying enough current to charge the battery, or the battery is discharging.
81
What does an ammeter/load meter indicate when it is connected in the generator output lead, and the engine is operating?
The current is leaving the generator, i.e., the electrical system load.
82
What is used to control the D.C. generator voltage?
Field current strength.
83
What D.C. alternator system component prevents battery reverse-current flow to the armature?
The rectifier.
84
Why are multiple generator systems paralleled?
To ensure that each generator shares the load.
85
How many phases are used in most aircraft A.C. alternator systems?
Three.
86
What determines the frequency of an alternator output?
The speed of rotation of the rotor and the number of poles.
87
How does a voltage regulator control the voltage of an alternator?
By regulating the voltage output of the D.C. exciter.
88
Name at least two methods that are used to maintain a 400 Hertz alternator output frequency on large turbojet/turbofan engines.
Constant speed drives and Integrated drive generators.
89
What are the major parts of a D.C. motor?
The armature, field, brush, and frame.
90
What are the three types of D.C. motors?
Series, shunt, and compound.
91
What are the components of a direct-cranking electric starter system?
An electric motor, reduction gears, and an automatic engaging and disengaging mechanism.
92
What are the operating modes of a turbine engine starter-generator?
It operates first as a starter, then as a generator after the engine is operating.
93
What is the size standard for electrical wire used in U.S.-manufactured aircraft?
The American Wire Gauge (AWG).
94
What is the maximum slack allowed between the supports of a single wire or bundle installation?
Not over 7/2”.
95
What kind of wire is used for wires running close to exhaust stacks or heating ducts?
Wire with high-temperature insulation material.
96
What is an indication of a dirty, worn starter commutator?
The starter is excessively noisy.
97
What type of D.C. motor is commonly used for an aircraft engine starter?
A series wound motor.
98
Why is a series wound motor commonly used as an aircraft engine starter?
Because it has a high starting torque under heavy load conditions.
99
What is the primary purpose of an aircraft reciprocating engine lubricant?
To reduce friction between moving parts.
100
What are two important characteristics relating to viscosity that an engine oil must possess?
It must be light enough to circulate freely and heavy enough to provide the proper oil film at engine operating temperatures.
101
What is the most critical lubrication point in a gas turbine engine?
The turbine bearing.
102
What may happen to an oil that is too low in viscosity at engine operating temperatures?
It is likely to become so thin that the oil film between moving parts is easily broken.
103
What factors must an engine manufacturer consider in determining the proper grade of oil for an engine?
Operating load, rotational speeds, and operating temperature.
104
What is the function of a dispersant additive as contained in ashless dispersant oil?
A dispersant helps keep an engine's interior clean by suspending sludge-forming contaminants in the oil until they can be trapped by the filter or drained out at an oil change.
105
Why must aircraft reciprocating engines use an oil with a relatively high viscosity?
Aircraft engines have large operating clearances, high operating temperatures, and high bearing pressures.
106
Why is an oil tank required to have expansion space?
To provide for thermal expansion and air in the return oil.
107
What is the purpose of an oil cooler bypass valve?
An oil cooler bypass valve directs oil through or around the cooler to keep the temperature within operating limits.
108
Where does the oil temperature bulb usually sense oil temperature?
At the engine oil inlet.
109
What does the presence of metal particles in an engine oil filter indicate?
Possible engine internal failure.
110
Name at least two areas of a turbine engine oil system where oil screens/filters may be located.
Scavenge system and at or just before the oil jets (Last chance).
111
What are some oil contaminants?
Moisture, acids, dirt, carbon, and metal particles.
112
What type of oil is used in turbine engine oil systems?
Synthetic oil.
113
What could be the cause of excessive oil consumption without evidence of oil leaks in a reciprocating engine?
Worn or broken piston rings.
114
What would be an indication of inadequate oil supply?
Low oil pressure and high oil temperature.
115
What would be an indication of an obstruction in the oil cooler passages?
High oil temperature.
116
What could cause oil foaming?
Diluted oil, contaminated oil, and the oil level are too high.
117
What are the two types of turbine engine oil coolers?
Air-cooled and fuel-cooled.
118
What controls oil pressure in a gear-type oil pressure pump?
An oil pressure relief valve.
119
What is the purpose of a magneto?
A magneto produces a high voltage that forces a spark to arc across a spark plug gap.
120
What are the three major circuits of a high-tension magneto system?
Magnetic, primary, and secondary.
121
What are the components of a high-tension magnetic circuit?
A permanent multipole rotating magnet, a soft iron core, and pole shoes.
122
In terms of the engine crankshaft position, when does the ignition event occur?
A specified number of crankshaft degrees before the top dead center on the compression stroke.
123
Where is the E-gap position in a magneto?
A few degrees beyond magnetic neutral.
124
What is the purpose of the capacitor in a magneto?
The capacitor prevents arcing at the points and aids in the collapsing of the magnetic field.
125
What happens when a magnetic rotor is in the E-gap position and the primary breaker points open?
The flow of current in the primary circuit stops, and a high rate of flux change occurs in the core, inducing a pulse of high voltage in the secondary, or the spark plug fires.
126
When an ignition switch is off in a magneto system, what is the condition of the ground circuit?
The circuit to ground is completed.
127
What is the purpose of using two magnetos in an engine ignition system?
System redundancy (safety factor) and improved combustion efficiency.
128
Which magneto is grounded when the magneto switch is selected to the right magneto?
The left magneto circuit.
129
What are the three events required to fire a spark plug in a cylinder when its piston is in the prescribed position?
The magneto is in the E-gap position, the breaker points are opening, and the distributor is electrically aligned with that cylinder.
130
What does a magneto timing light indicate?
It indicates the exact instant that the magneto points open.
131
What is the main concern when preparing a magneto for installation?
Internal timing.
132
Are turbine engine spark igniters generally susceptible to carbon fouling? Explain.
No, because the high-energy sparks they produce clean off any deposits that form on the firing end.
133
The remaining service life of the brushes typically used in many starter generators can be determined by visual inspection of what?
The amount of wear groove remaining on the brushes.
134
What is the function of a duty cycle concerning a turbine engine ignition system?
A duty cycle allows the operation of the ignition system for a given amount of time, to be followed by a minimum specified cooling-down period.
135
What are typically the three main components of turbine engine ignition systems?
Ignition exciters, high-tension leads, and igniters.
136
Name three sources of high-volume, low-pressure compressed air commonly used for starting jet transport aircraft equipped with air turbine starters.
An on-board auxiliary power unit (APU), a ground power unit (GPU), and compressor bleed air from an already running engine.
137
Between field and armature windings in starter-generators, which ordinarily receive current for operation in the start mode?
Generally, both the field and the armature receive current for operation in the start mode.
138
Name two parts of a starter generator that commonly require periodic inspection to ensure that they do not wear beyond operational limits.
The commutator and brushes.
139
How are high-temperature noxious gases removed and disposed of in an operating reciprocating engine?
By the engine exhaust system.
140
What is the primary function of an exhaust system (regarding safety)?
To protect against the potentially destructive action of exhaust gases.
141
What are the two types of reciprocating engine exhaust systems?
The short stack system and the collector system.
142
What type of exhaust system is used on turbocharged engines?
The collector system.
143
What material is typically used to make exhaust system muffler shrouds?
A sheet of stainless steel.
144
What drawback of using collector-type exhaust systems is more than offset when used on turbocharged engines?
The loss of horsepower due to exhaust system back pressure.
145
Why is an exhaust system failure considered a severe hazard?
It can result in carbon monoxide poisoning, loss of engine power, or fire.
146
Why should lead, zinc, or galvanized marks not be made on exhaust systems?
The marks cause a change in molecular structure when heated and will cause cracks.
147
What is an indication of an exhaust gas leak?
A flat gray or sooty black deposit in the area of the leak.
148
How are internal baffles or diffusers of the exhaust system inspected?
The exhaust system is disassembled as necessary for visual inspection.
149
How can the failure of the exhaust system's internal baffles or diffusers cause a loss of engine power?
By restricting the flow of exhaust gases.
150
What happens to engine power when a heat exchanger leaks exhaust gases into the engine induction system?
Loss of power.
151
Where are exhaust manifold and stack failures usually found?
At welded or clamped points, and flanges.
152
What is the common cause of the turbocharger waste gate sticking?
Coke deposits or carbon buildup.
153
Why are turbocharged exhaust system leaks very damaging at high altitudes?
Pressure differential will cause the leak to escape with torch-like intensity.
154
What are exhaust system choke deposits?
Excessive carbon buildup.
155
What happens to turbine engine performance if the exhaust nozzle area is changed?
The performance and exhaust gas temperature change.
156
What are the components of a typical turbine exhaust nozzle?
A tail cone, exhaust duct, and support struts.
157
What is the function of the thermocouple probes in a turbine exhaust tailpipe?
To measure exhaust gas temperature.
158
What change does a noise suppressor make to the noise frequency to help reduce older turbojet engine noise?
It converts low-frequency sound into high-frequency sound.
159
What are thrust reversers primarily used for?
To aid in decelerating an aircraft after landing.
160
Name two types of thrust reverser systems commonly used.
Mechanical blockage (or clamshell) type, and Cascade (or aerodynamic blockage) type.
161
Are thrust reversers generally able to produce a maximum reverse thrust approximately equal to an engine's full forward thrust?
No. An engine's full reverse thrust is usually substantially less than its full forward thrust.
162
What are the hazards of operating some thrust reversers at low ground speeds?
Re-ingestion of hot exhaust gases and ingestion of foreign objects when stirred up by the deflected exhaust gases.
163
How do you determine the reparability of a damaged propeller blade?
By reference to the manufacturer's maintenance manual.
164
What is the purpose of propellers?
The blades produce forces that create thrust to pull or push the airplane through the air.
165
What is a fixed-pitch propeller?
A fixed-pitch propeller has a built-in blade angle that cannot be changed.
166
What type of blade angle changes will occur on a propeller that is pitch-controlled by a blade propeller angle governor during a constant power dive?
The blade angle increases to overcome overspeeding.
167
Other than maintaining a constant speed, what are the two actions of some controllable propellers?
Reverse pitch and feathering.
168
What is the purpose of the metal tipping fastened to a wooden propeller's leading edge and tip?
To protect the propeller from damage.
169
When engine vibration is reported, what should be checked to determine if it is caused by the engine or propeller?
Blade tracking and blade angle setting.
170
What is blade tracking?
Blade tracking determines the positions of the propeller blade tips in relation to each other.
171
What may be used to determine propeller blade angle?
A propeller protractor.
172
How should aluminum propeller blades and hubs be cleaned?
The propeller should be cleaned according to the manufacturer's recommendations.
173
What positions of a two-bladed propeller are used during a static balance test?
Vertical and horizontal.
174
What two forces are balanced in a propeller governor in an on-speed condition?
Speeder spring and flyweight.
175
On light aircraft propellers, what is the effect of centrifugal force acting on propeller blade counterweights?
Centrifugal force acting on the counterweights serves to increase propeller blade pitch.
176
What happens to a constant speed feathering propeller governor oil pressure drops to zero?
The propeller will feather.
177
What three things does a typical constant-speed propeller governor accomplish when operating?
It boosts engine oil pressure before it enters the propeller hub, controls the amount of oil that flows to the propeller, and senses the rotational speed of the engine.
178
What types of systems are used for propeller ice control?
Fluid and electrical.
179
What type of nondestructive testing should be accomplished on a propeller after blending?
The procedures that are recommended by the manufacturer.
180
To what do the terms alpha range and beta range pertain?
Both terms pertain to operating modes of turboprop reversible-pitch propellers.
181
What is the alpha range of a turboprop?
The alpha range is an operation in the constant speed mode (usually in-flight).
182
What is the beta range of a turboprop?
The beta range is an operation in the minimum or zero thrust, and negative (reverse) thrust modes (usually for ground handling and taxiing).
183
What is the purpose of an oil accumulator connected to a propeller governor?
To provide unfeathering oil pressure.
184
How is feathering accomplished on a constant-speed propeller?
Releasing the governor oil pressure allows the counterweights and feathering spring to feather the propeller.
185
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.
186
What can be used to clean a wooden propeller?
Warm water and mild soap, together with a brush or cloth.
