Powerplant Ignition and Starting Systems
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132 Terms
When using a timing light to time a magneto to an aircraft engine, the magneto switch should be placed in the
BOTH position.
2 multiple choice options
What would be the result if a magneto breaker point mainspring did not have sufficient tension?
The points will float or bounce.
2 multiple choice options
The purpose of an under current relay in a starter-generator system is to
disconnect power from the starter-generator and ignition when sufficient engine speed is reached.
2 multiple choice options
Why do turbine engine ignition systems require high energy?
To ignite the fuel under conditions of high altitude and low temperatures.
2 multiple choice options
Which of the following statements most accurately describes spark plug heat range?
A cold plug is designed so that the insulator tip is reasonably short to hasten the rate of heat transfer from the tip through the spark plug shell to the cylinder head.
2 multiple choice options
Spark plug heat range is determined by
its ability to transfer heat to the cylinder head.
2 multiple choice options
When timing a magneto internally, the alignment of the timing marks indicates that the
magnets are in the E-gap position.
2 multiple choice options
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.
2 multiple choice options
(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.
2 multiple choice options
Magneto breaker points must be timed to open when the
greatest magnetic field stress exists in the magnetic circuit.
2 multiple choice options
Which of the following would be cause for rejection of a spark plug?
Insulator tip cracked.
2 multiple choice options
If staggered ignition timing is used, the
spark plug nearest the exhaust valve will fire first.
2 multiple choice options
What component of a dual magneto is shared by both ignition systems?
Rotating magnet.
2 multiple choice options
What is the radial location of the two north poles of a four-pole rotating magnet in a high-tension magneto?
180° apart.
2 multiple choice options
When the ignition switch of a single (reciprocating) engine aircraft is turned to the OFF position,
the primary circuits of both magnetos are grounded.
2 multiple choice options
(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 gapping massive-electrode spark plugs, a wire gauge should be inserted between the center and ground electrodes while moving the ground electrode in order to avoid setting the gap too close.
Regarding the above statements,
only No. 1 is true.
2 multiple choice options
In a high-tension ignition system, a primary capacitor of too low a capacity will cause
the breaker contacts to burn.
2 multiple choice options
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.
2 multiple choice options
Aircraft magneto housings are usually ventilated in order to
provide cooling and remove corrosive gases produced by normal arcing.
2 multiple choice options
Shielding is used on spark plug and ignition wires to
prevent interference with radio reception.
2 multiple choice options
Magneto timing drift is caused by erosion of the breaker points and
wear of the cam followers.
2 multiple choice options
A magneto ignition switch is connected
parallel to the breaker points.
2 multiple choice options
How is the strength of a magneto magnet checked?
Hold the points open and check the output of the primary coil with an ac ammeter while operating the magneto at a specified speed.
2 multiple choice options
The greatest density of flux lines in the magnetic circuit of a rotating magnet-type magneto occurs when the magnet is in what position?
Full alignment with the field shoe faces.
2 multiple choice options
Which of the following are included in a typical turbine engine ignition system?
1. Two igniter plugs.
2. Two transformers.
3. One exciter unit.
4. Two intermediate ignition leads.
5. Two low-tension igniter leads.
6. Two high-tension igniter leads.
1, 3, 6.
2 multiple choice options
The purpose of a safety gap in a magneto is to
protect the high-voltage winding from damage.
2 multiple choice options
Why are turbine engine igniters less susceptible to fouling than reciprocating engine spark plugs?
The high-intensity spark cleans the igniter.
2 multiple choice options
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
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.
2 multiple choice options
If a spark plug lead becomes grounded, the
magneto will not be affected.
2 multiple choice options
What is the electrical location of the primary capacitor in a high-tension magneto?
In parallel with the breaker points.
2 multiple choice options
Why are high-tension ignition cables frequently routed from the distributors to the spark plugs in flexible metallic conduits?
To reduce the effect of the high-frequency electromagnetic waves emanated during operation.
2 multiple choice options
What is the relationship between distributor and crankshaft speed of aircraft reciprocating engines?
The distributor turns at one-half crankshaft speed.
2 multiple choice options
If the ground wire of a magneto is disconnected at the ignition switch, the result will be the
engine will not stop running when the ignition switch is turned off.
2 multiple choice options
The term 'reach,' as applied to spark plug design and/or type, indicates the
linear distance from the shell gasket seat to the end of the threads on the shell skirt.
2 multiple choice options
When removing a shielded spark plug, which of the following is most likely to be damaged?
Core insulator.
2 multiple choice options
If new breaker points are installed in a magneto on an engine, it will be necessary to time the
magneto internally and the magneto to the engine.
2 multiple choice options
Igniter plugs used in turbine engines have a long service life because they
do not require continuous operation.
2 multiple choice options
What are two parts of a distributor in an aircraft engine ignition system?
1. Coil.
2. Block.
3. Stator.
4. Rotor.
5. Transformer.
2 and 4.
2 multiple choice options
Magneto breaker point opening relative to the position of the rotating magnet and distributor rotor (internal timing) can be set most accurately
during assembly of the magneto before installation on the engine.
2 multiple choice options
What is a result of 'flashover' in a distributor?
Conductive carbon trail.
2 multiple choice options
The spark is produced in a magneto ignition system when the breaker points are
beginning to open.
2 multiple choice options
What will be the effect if the spark plugs are gapped too wide?
Hard starting.
2 multiple choice options
The secondary coil of a magneto is grounded through the
primary coil.
2 multiple choice options
When will the voltage in the secondary winding of a magneto, installed on a normally operating engine, be at its highest value?
Just prior to spark plug firing.
2 multiple choice options
When does battery current flow through the primary circuit of a battery ignition coil?
When the breaker points are closed and the ignition switch is on.
2 multiple choice options
Airflow to the pneumatic starter from a ground unit is normally prevented from causing starter overspeed during engine start by
activation of a flyweight cutout switch.
2 multiple choice options
The E-gap angle is usually defined as the number of degrees between the neutral position of the rotating magnet and the position
where the contact points open.
2 multiple choice options
Alignment of the marks provided for internal timing of a magneto indicates that the
magneto is in E-gap position.
2 multiple choice options
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 starter drop out because
the starter will overspeed at a given N^2.
2 multiple choice options
Thermocouples are usually inserted or installed on the
hottest cylinder of the engine.
2 multiple choice options
The capacitor-type ignition system is used almost universally on turbine engines primarily because of its high voltage and
high-heat intensity.
2 multiple choice options
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.
2 multiple choice options
The spark occurs at the spark plug when the ignition's
primary circuit is broken.
2 multiple choice options
What is the approximate position of the rotating magnet in a high-tension magneto when the points first close?
Full register.
2 multiple choice options
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
drive shaft shear point.
2 multiple choice options
Which statement is correct regarding the ignition system of a turbine engine?
The system is normally de-energized as soon as the engine starts.
2 multiple choice options
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.
2 multiple choice options
A spark plug's heat range is the result of
its ability to transfer heat from the firing end of the spark plug to the cylinder head.
2 multiple choice options
Which of the following could cause damage to the nose ceramic or to the electrode of an aircraft spark plug?
Improper gapping procedure.
2 multiple choice options
When internally timing a magneto, the breaker points begin to open when the rotating magnet is
a few degrees past the neutral position.
2 multiple choice options
What is the purpose of a safety gap in some magnetos?
To discharge the secondary coil's voltage if an open occurs in the secondary circuit.
2 multiple choice options
The amount of voltage generated in any magneto secondary coil is determined by the number of windings and by the
rate of collapse of the magnetic field around the primary coil.
2 multiple choice options
(Refer to Figure 5.) Which malfunctions will allow the igniters to operate normally during start but be inoperative when tested?
1. Conductor No. 14 broken.
2. Conductor No. 10 broken.
3. Conductor No. 15 broken.
4. Conductor No. 12 broken.
1 or 3.
2 multiple choice options
Which of the following statements regarding magneto switch circuits is NOT true?
In the BOTH position, the right and left magneto circuits are grounded.
2 multiple choice options
The constrained-gap igniter plug used in some gas turbine engines operates at a cooler temperature because
the construction is such that the spark occurs beyond the face of the combustion chamber liner.
1 multiple choice option
(Refer to Figure 5.) Which malfunctions will allow the igniters to operate when tested but be inoperative during a start attempt?
1. Conductor No. 10 broken.
2. Conductor No. 11 broken.
3. Ignition relay inoperative.
4. Conductor No. 12 broken.
1 or 3.
2 multiple choice options
In a high-tension ignition system, the current in the magneto secondary winding is
induced when the primary circuit is interrupted.
2 multiple choice options
The electrical circuit from the spark plug back to the magneto is completed by grounding through the
engine structure.
2 multiple choice options
(Refer to Figure 5.) If wire No. 8 is broken or disconnected after starter rotation is initiated, and the power lever is advanced, the
starting sequence will continue normally.
2 multiple choice options
In order to turn a magneto off, the primary circuit must be
grounded.
2 multiple choice options
How many secondary coils are required in a low-tension ignition system on an 18-cylinder engine?
36
2 multiple choice options
The primary advantage of pneumatic (air turbine) starters over comparable electric starters for turbine engines is
high power-to-weight ratio.
2 multiple choice options
What should be used to clean grease or carbon tracks from capacitors or coils that are used in magnetos?
Acetone.
2 multiple choice options
When performing a magneto ground check on an engine, correct operation is indicated by
a slight drop in RPM.
2 multiple choice options
When internally timing a magneto, the breaker points begin to open when
the magnet poles are a few degrees beyond the neutral position.
2 multiple choice options
The type of ignition system used on most turbine aircraft engines is
capacitor discharge.
2 multiple choice options
Capacitance afterfiring in most modern spark plugs is reduced by the use of
a built-in resistor in each plug.
2 multiple choice options
Upon inspection of the spark plugs in an aircraft engine, the plugs were found caked with a heavy black soot. This indicates
a rich mixture.
2 multiple choice options
The purpose of staggered ignition is to compensate for
diluted fuel/air mixture around exhaust valve.
2 multiple choice options
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.
2 multiple choice options
A clicking sound heard at engine coast-down in a pneumatic starter incorporating a sprag clutch ratchet assembly is an indication of
the pawls re-contacting and riding on the ratchet gear.
2 multiple choice options
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.
2 multiple choice options
Using a cold spark plug in a high-compression aircraft engine would probably result in
normal operation.
2 multiple choice options
A certain nine-cylinder radial engine used a noncompensated 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 engine speed?
Distributors.
2 multiple choice options
Great caution should be exercised in handling damaged hermetically sealed turbine engine igniter transformer units because
some contain radioactive material.
2 multiple choice options
Spark plugs are considered worn out when the
electrodes have worn away to about one-half of their original dimensions.
2 multiple choice options
When the switch is off in a battery ignition system, the primary circuit is
opened.
2 multiple choice options
(Refer to Figure 5.) With power applied to the bus bar, what wire supplies standby power to the starter relay contact?
4
2 multiple choice options
As an aircraft engine's speed is increased, the voltage induced in the primary coil of the magneto
increases.
2 multiple choice options
(Refer to Figure 5.) When an external power source is connected to the aircraft,
the battery cannot be connected to the bus.
2 multiple choice options
Which of the following breaker point characteristics is associated with a faulty capacitor?
Coarse grained.
2 multiple choice options
When using an electric starter motor, the current flow through it
is highest at the start of motor rotation.
2 multiple choice options
In a four-stroke cycle aircraft engine, when does the ignition event take place?
Before the piston reaches TDC on compression stroke.
2 multiple choice options
Which of the following are distinct circuits of a high tension magneto?
Magnetic, primary, and secondary.
2 multiple choice options
The magnetic circuit of a magneto consists of a permanent multi-pole rotating magnet. The core is made of
soft iron.
2 multiple choice options
In a typical starter-generator system, under which of the following starting circumstances may it be necessary to use the start stop button?
Hung start.
2 multiple choice options
What components make up the magnetic system of a magneto?
Rotating magnet, the pole shoes, the pole shoe extensions, and the coil core.
2 multiple choice options
Sharp bends should be avoided in ignition leads primarily because
weak points may develop in the insulation through which high tension current can leak.
2 multiple choice options
If it is found that a shielded ignition system does not adequately reduce ignition noise, it may be necessary to install
a filter between the magneto and magneto switch.
2 multiple choice options
Advantages of dual ignition in aircraft engines include providing a backup magneto system, increasing the output power of the engine, and
increasing the output power of the engine.
2 multiple choice options