Ignition and Starting Systems Flashcards
(132 cards)
1
Q
The magnetic circuit of a magneto consists of a permanent multi-pole rotating magnet. The core is made of what?
A
soft iron.
2
Q
How is the strength of a magneto magnet checked?
A
Hold the points open and check the output of the primary coil with an AC ammeter while operating the magneto at a specified speed.
3
Q
The E-gap angle is usually defined as the number of degrees between the neutral position of the rotating magnet and the position…
A
where the contact points open.
4
Q
The greatest density of flux lines in the magnetic circuit of a rotating magnet-type magneto occurs when the magnet is in what position?
A
Full alignment with the field shoe faces.
5
Q
Magneto breaker point opening relative to the position of the rotating magnet and distributor rotor (internal timing) can be set most accurately…
A
during assembly of the magneto before installation on the engine.
6
Q
Why are high-tension ignition cables frequently routed from the distributors to the spark plugs in flexible metallic conduits?
A
To reduce the effect of the high-frequency electromagnetic waves emanated during operation.
7
Q
What will be the result of increasing the gap of the breaker points in a magneto?
A
Advance the spark and decrease its intensity.
8
Q
What is the purpose of a safety gap in some magnetos?
A
To discharge the secondary coil’s voltage if an open occurs in the secondary circuit.
9
Q
When timing a magneto internally, the alignment of the timing marks indicates that the…
A
magnets are in the E-gap position.
10
Q
When internally timing a magneto, the breaker points begin to open when the rotating magnet is what?
A
a few degrees past the neutral position.
11
Q
Magneto timing drift is caused by erosion of the breaker points and what?
A
wear of the cam followers.
12
Q
What is the electrical location of the primary capacitor in a high-tension magneto?
A
In parallel with the breaker points.
13
Q
In a high-tension ignition system, the current in the magneto secondary winding is what?
A
induced when the primary circuit is interrupted.
14
Q
When a “Shower of Sparks” ignition system is activated at an engine start, a spark plug fires…
A
only while both the retard and advance breaker points are open.
15
Q
What is the radial location of the two north poles of a four-pole rotating magnet in a high-tension magneto?
A
180 degrees apart.
16
Q
Magneto pole shoes are generally made of what?
A
laminations of high-grade soft iron.
17
Q
Capacitance afterfiring in most modern spark plugs is reduced by the use of what?
A
a built-in resistor in each plug.
18
Q
What components make up the magnetic system of a magneto?
A
Rotating magnet, the pole shoes, the pole shoe extensions, and the coil core.
19
Q
In an aircraft ignition system, one of the functions of the capacitor is to what?
A
facilitate a more rapid collapse of the magnetic field in the primary coil.
20
Q
When will the voltage in the secondary winding of a magneto, installed on a normally operating engine, be at its highest value?
A
Just prior to spark plug firing.
21
Q
When the switch is off in a battery ignition system, the primary circuit is what?
A
opened.
22
Q
As an aircraft engine’s speed is increased, the voltage induced in the primary coil of the magneto…
A
increases.
23
Q
When internally timing a magneto, the breaker points begin to open when what?
A
the magneto poles are a few degrees beyond the neutral position.
24
Q
The purpose of a safety gap in a magneto is to what?
A
protect the high-voltage winding from damage.
25
A defective primary capacitor in a magneto is indicated by what?
burned and pitted breaker points.
26
How many secondary coils are required in a low-tension ignition system on an 18-cylinder engine?
36.
27
A magneto ignition switch is connected...
parallel to the breaker points.
28
The spark is produced in a magneto ignition system when the breaker points are what?
beginning to open.
29
Shielding is used on spark plug and ignition wires to what?
prevent interference with radio reception.
30
What is the purpose of using an impulse coupling with a magneto?
To produce a momentary high rotational speed of the magneto.
31
The purpose of staggered ignition is to compensate for what?
diluted fuel/air mixture around exhaust valve.
32
Aircraft magneto housings are usually ventilated in order to what?
provide cooling and remove corrosive gases produced by normal arcing.
33
Failure of an engine to cease firing after turning the magneto switch off is an indication of what?
an open P-lead to ground.
34
Alignment of the marks provided for internal timing of a magneto indicates that the what?
magneto is in E-gap position.
35
When using a timing light to time a magneto to an aircraft engine, the magneto switch should be place in the what?
BOTH position.
36
What is the difference between a low-tension and a high-tension engine ignition system?
A low-tension system uses a transformer coil near the spark plugs to boost voltage, while the high-tension system voltage is constant from the magneto to the spark plugs.
37
What test instrument could be used to test an ignition harness for suspected leakage?
A high tension lead tester.
38
The amount of voltage generated in any magneto secondary coil is determined by the number of windings and by the what?
rate of collapse of the magnetic field around the primary coil.
39
Magneto breaker points must be timed to pen when the what?
greatest magnetic field stress exists in the magnetic circuit.
40
In reference to a "Shower of Sparks" ignition system,
(1) the retard breaker points are designed to keep the affected ignition system operating if the advance breaker points should fail during normal engine operation (after start).
(2) the timed opening of the retard breaker points is designed to prevent engine "kickback" during start.
Only 2 is true.
41
The capacitor-type ignition system is used almost universally on turbine engines primarily because of its high voltage and what?
long life.
42
In a low-tension ignition system, each spark plug requires an individual...
secondary coil.
43
A certain nine-cylinder radial engine used a non-compensated single-unit, dual-type magneto with a four-pole rotating magnet and separately mounted distributors. Which of the following will have the lowest RPM at any given speed?
Distributors.
44
What will be the effect if the spark plugs are gapped too wide?
Hard starting.
45
When removing a shielded spark plug, which of the following is most likely to be damaged?
Core insulator.
46
What likely effect would a cracked distributor rotor have on a magneto?
Ground the secondary circuit through the crack.
47
How does the ignition system of a gas turbine engine differ from that of a reciprocating engine?
A high-energy spark is required for ignition.
48
In a turbine engine DC capacitor discharge ignition system, where are the high-voltage pulses formed?
At the triggering transformer.
49
Which of the following breaker points characteristics is associated with a faulty capacitor?
Coarse grained.
50
How are most radial engine spark plug wires connected to the distributor block?
By use of cable-piercing screws.
51
Thermocouples are usually inserted or installed on the what?
hottest cylinder of the engine.
52
Capacitance afterfiring of a spark plug is caused by what?
the stored energy in the ignition shielded lead unloading after normal timed ignition.
53
If it found that a shielded ignition system does not adequately reduce ignition noise, it may be necessary to install what?
a filter between the magneto and magneto switch
54
When a magneto is operating, what is the probable cause for a shift in internal timing?
The cam follower wear and/or the breaker points wear.
55
Why are turbine engine igniters less susceptible to fouling than reciprocating engine spark plugs?
The high-intensity spark cleans the igniter.
56
The constrained-gap igniter plug used in some gas turbine engines operates at a cooler temperature because what?
The construction is such that the spark occurs beyond the face of the combustion chamber liner.
57
What should be used to clean grease or carbon tracks from capacitors or coils that are used in magnetos?
Acetone.
58
Generally, when removing a turbine engine igniter plug, in order to eliminate the possibility of the technician receiving a lethal shock, the ignition switch is turned off and what?
the igniter lead is disconnected from the plug and the center electrode grounded to the engine after disconnecting the transformer-exciter input lead and waiting the prescribed time.
59
Great caution should be exercised in handling damaged hermetically sealed turbine engine igniters transformer units because...
some contain radioactive material.
60
Igniter plugs used in turbine engines have a long service life because they what?
do not require continuous operation.
61
The electrical circuit from the spark plug back to the magneto is completed by grounding through the what?
engine structure.
62
Spark plugs are considered worn out when the what?
electrodes have worn away to about one-half of their original dimensions.
63
Which of the following could cause damage to the nose ceramic or to the electrode of an aircraft spark plug?
Improper gapping procedure.
64
Sharp bends should be avoided in ignition leads primarily because what?
weak points may develop in the insulation through which high tension current can leak.
65
In a high-tension ignition system, a primary capacitor of too low a capacity will cause what?
the breaker contacts to burn.
66
Which of the following, obtained during magneto check at 1,700 RPM, indicates a short (grounded) circuit between the right magneto primary and the ignition switch?
BOTH - 1,700 RPM, R - 0 RPM, L - 1,700 RPM, OFF - 0 RPM.
67
If an aircraft ignition switch is turned off and the engine continues to run normally, the trouble is probably caused by what?
an open ground lead in the magneto.
68
Which statement is correct regarding the ignition system of a turbine engine?
The system is normally de-energized as soon as the engine starts.
69
When the ignition switch of a single (reciprocating) engine aircraft is turned to the OFF position, ...
the primary circuits of both magnetos are grounded.
70
A spark plug's heat range is the result of what?
its ability to transfer heat from the firing end of the spark plug to the cylinder head.
71
If staggered ignition timing is used, the what?
spark plug nearest the exhaust valve will fire first.
72
The term "reach," as applied to spark plug design and/or type, indicates the what?
linear distance from the shell gasket seat to the end of the threads on the shell skirt.
73
The numbers appearing on the ignition distributor block indicate the what?
sparking order of the distributor.
74
When testing a magneto distributor block for electrical leakage, which of the following pieces of test equipment should be used?
A high-tension harness tester.
75
(1) The platinum and iridium ground electrodes used on fine wire spark plugs are extremely brittle and can be broken if they are improperly handled or adjusted.
(2) When gaping massive-electrode spark plugs, a wire gauge should be inserted between the center and ground electrodes while moving the ground electrodes in order to avoid setting the gap too close.
Only 1 is true.
76
Hot spark plugs are generally used in aircraft powerplants...
with comparatively low operating temperatures.
77
If a spark plug lead becomes grounded, the what?
magneto will not be affected.
78
Which of the following statements regarding magneto switch circuits is NOT true?
In the BOTH position, the right and left magneto circuits are grounded.
79
Which of the following statements most accurately describes spark plug heat range?
A cold plug is designed so that the insulator top is reasonably short to hasten the rate of heat transfer from the tip through the spark plug shell to the cylinder head.
80
When does battery current flow through the primary circuits of a battery ignition coil?
When the breaker points are closed and the ignition switch is on.
81
In order to turn a magneto off, the primary circuits must be what?
grounded.
82
When performing a magneto ground check on an engine, correct operation is indicated by what?
a slight drop in RPM.
83
Defective spark plugs will cause the engine to run rough...
at all speeds.
84
Defective spark plugs will cause the engine to run rough...
at all speeds.
85
Which of the following would be cause for rejection of a spark plug?
Insulator tip cracked.
86
What will be the result of using too hot a spark plug?
Preignition.
87
Upon inspection of the spark plugs in an aircraft engine, the plugs were found caked with a heavy black soot. This indicates what?
a rich mixture.
88
Spark plug heat range is determined by what?
its ability to transfer heat to the cylinder head.
89
Ignition check during engine runup indicates excessive RPM drop during operation on the right magneto. The major portion of the RPM loss occurs rapidly after switching to the right magneto position (fast drop). The most likely cause is what?
faulty or fouled spark plugs.
90
If new breaker points are installed in a magneto on an engine, it will be necessary to time the what?
magneto internally and the magneto to the engine.
91
Using a cold spark plug in a high-compression aircraft engine would probably result in what?
normal operation.
92
Spark plug fouling caused by lead deposits occurs most often...
when cylinder head temperatures are relatively low.
93
In a four-stroke cycle aircraft engine, when does the ignition event take place?
Before the piston reaches TDC on compression stroke.
94
When installing a magneto on an engine, the what?
piston in the cylinder 1 must be a prescribed number of degrees before top center on the compression stroke.
95
The spark occurs at the spark plug when the ignition's...
primary circuits is broken.
96
The type of ignition system used on most turbine aircraft engines is what?
capacitor discharge.
97
Ignition check during engine runup indicates a slow drop in RPM. This is usually caused by what?
incorrect ignition timing or valve adjustment.
98
If the ground wire of a magneto is disconnected at the ignition switch, the result will be the what?
engine will not stop running when the ignition switch is turned off.
99
Advantages of dual ignition in aircraft engines include providing a backup magneto system, gives a more complete and quick combustion of the fuel, and...
increasing the output power of the engine.
100
How does high-tension ignition shielding tend to reduce radio interference?
Receives and grounds high-frequency waves coming from the magneto and high-tension ignition leads.
101
Which of the following are distinct circuits of a high tension magneto?
Magnetic, primary, and secondary.
102
What are two parts of a distributor in an aircraft engine ignition system?
Block and rotor.
103
What is a result of "flashover" in a distributor?
Conductive carbon trail.
104
What is the relationship between distributor and crankshaft speed of aircraft reciprocating engines?
The distributor turns at one-half crankshaft speed.
105
Why do turbine engine ignition systems require high energy?
To ignite the fuel under conditions of high altitude and low temperatures.
106
Which of the following are included in a typical turbine engine ignition system?
Two igniter plus, one exciter unit, and two high-tension igniter leads.
107
At what RPM is a reciprocating engine ignition switch check made?
The slowest possible RPM.
108
What is the approximate position of the rotating magnet in a high-tension magneto when the points first close?
Full register.
109
What component of a dual magneto is shared by both ignition systems?
Rotating magnet.
110
What would be the result if a magneto breaker points mainspring did not have sufficient tension?
The points will float or bounce.
111
The secondary coils of a magneto is grounded through the what?
primary coil.
112
In the aircraft magneto system, if the P-lead is disconnected, the magneto will be what?
on regardless of ignition switch position.
113
(Refer to Figure 5.) With power applied to the bus bar, what wire supplies standby power to the starter relay contact?
4.
114
(Refer to Figure 5.) With power applied to the bus bar, what switch changes will allow the ignition exciters test switch to function?
Engine master switch and ignition switch.
115
(Refer to Figure 5.) The type of system depicted is capable of operating with what?
either battery or external power.
116
(Refer to Figure 5.) If wire 8 is broken or disconnected after starter rotation is initiated, and the power lever is advanced, the what?
starting sequence will continue normally.
117
(Refer to Figure 5.) When an external power source is connected to the aircraft,
the battery cannot be connected to the bus.
118
The purpose of an under current relay in a starter generator system is to what?
disconnect power from the starter-generator and ignition when sufficient engine speed is reached.
119
In a typical starter-generator system, under which of the following starting circumstances may it be necessary to use the start stop switch?
Hung start.
120
(Refer to Figure 5.) Which malfunctions will allow the igniters to operate when tested but be inoperative during a start attempt?
Wire 10 is broken and/or ignition relay is inoperative.
121
(Refer to Figure 5.) Which malfunctions will allow the igniters to operate during start but be inoperative when tested?
Wire 14 or 15 is broken.
122
When using an electric starter motor, current usage...
is highest at the start of motor rotation.
123
When using an electric starter motor, the current flow through it...
is highest at the start of motor rotation.
124
The primary advantage of pneumatic (air turbine) starters over comparable electric starters for turbine engines is what?
its high power-to-weight ratio.
125
A clicking sound heard at engine coast-down in a pneumatic starter incorporating a sprag clutch ratchet assembly is an indication of what?
the pawls recontacting and riding on the ratchet gear.
126
Pneumatic starters are usually designed with what types of airflow impingement systems?
Radial inward flow turbine and axial-flow turbine.
127
Inspection of pneumatic starters by maintenance technicians usually includes checking the what?
oil level and magnetic drain plug condition.
128
Air turbine starters are generally designed so that reduction gear distress or damage may be detected by what?
inspection of a magnetic chip detector.
129
Airflow to the pneumatic starter from a ground unit is normally prevented from causing starter over speed during engine start by what?
activation of a flyweight cutout switch.
130
A safety feature usually employed in pneumatic starters that is used if the clutch does not release from the engine drive at the proper time during start is the what?
drive shaft shear point.
131
A safety feature usually employed in direct-cranking starters that is used to prevent the starter from reaching burst speed is the what?
stator nozzle design that chokes airflow and stabilizes turbine wheel speed.
132
In the event a pneumatic start valve will not operate and the manual override must be used, the starter T-handle must be closed at scheduled start drop out because what?
The starter will over speed at a given N2.
