05. Piston Engine: Starting and Ignition Flashcards
Thinking of petrol and diesel engines, what are the 2 methods of igniting mixture
- Spark plugs
- Spontaneous combustion
Spark plugs create a spark to ignite the mixture
Spontaneous combustion is caused by compressing the mixture to increase the temperature
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What is an electric starter motor powered by during a start sequence
BATTERY
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Once an engine is started, what is the name of the component that disengages the drive from the motor
OVERRUN CLUCTH
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What is the purpose of an overrun clutch
DISENGAGE DRIVE from MOTOR
As soon as the engine starts during a start sequence, the ovverun clutch disengages the drive from the motor
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What must a pilot do if the starter-warning light remains illuminated 30 seconds after start
SHUTDOWN ENGINE
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What does an illuminated starter warning light mean
DRIVE GEAR ENGAGED
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What is the job of an alternator belt
SUPPLY POWER
To aircraft electrical system
Pg 127
What is the purpose of a magneto
POWER SPARK PLUGS
Generate high tension electricity
Pg 127
Critical components of an ignition system are ____
This ensures a single point of failure does not result in total loss of ____
- DUPLICATED
- ENGINE POWER
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How many magnetos does a normal aero engine have
2
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- The right magneto supplies power to which banks of sparkplugs
- The left magento suppliers power to which banks of sparkplugs
- RIGHT = UPPER RIGHT, lower left
- LEFT = UPPER LEFT, lower right
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A magneto provides HIGH or LOW voltage to spark plugs
HIGH
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A magneto is what type of generator
AC GENERATOR
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The secondary winding of many turns of wire around a primary winding in a magneto allows a high voltage to be induced in the secondary winding. This effectively makes a magneto a what
TRANSFORMER
Multiplying the number of wire turns in the secondary winding steps up the power voltage being produced, thus transforming the output to a higher voltage
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A magneto has MORE or LESS turns of wire in the primary winding than the secondary winding
LESS
primary (less) < SECONDARY (MORE)
Primary coil has less turns than secondary coil.
The primary coil induces a higher voltage in the secondary coil
This effectively makes the magneto a transformer
Pg 129
Magneto
The generator section comprises of how many poles
4
4-pole rotating permanent magnet
Pg 129
Magneto
The stator is made up of which material
SOFT IRON
Pg 129
Magneto
The permanent magnets are driven by what
ENGINE
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Magneto
How is the circuit in the primary winding continuously broken and remade
CONTACT BREAKER
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Magneto
What is the purpose of a contact breaker when used in the primary winding
CONTINUOUSLY BREAK and REMAKE CIRCUIT
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Magneto
What are the 2 effects of breaking and remaking the circuit in the primary winding through the use of a contact breaker
- PULSES - Converts continuous flow of AC
- COLLAPSE MAGNETIC FIELD
Collapsing the magnetic field around the primary winding produces a surge of energy in the secondary winding
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Magneto
What is the result of the contact breaker opening and collapsing the magnetic field in the primary winding with regards to the spark plugs
VERY HIGH VOLTAGE
low current pulses
Collapsing of the magnetic field produces a surge of energy in the secondary winding
Overall result is a very high voltage, low current pulse provided to the spark plugs
Pg 130
Magneto
What is a risk to the contact breaker when then magent field is collapsed in the primary winding
ARCHING
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Magneto
What is fitted in parallel to the contact breaker to prevent arching
CAPACITOR
(or condeser)
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Magneto
What is the purpose of a capacitor being fitted in parallel to the contact breaker
PREVENT ARCHING
Also helps ensure highest possible voltage induced in secondary winding
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Magneto
What component delivers electrical pulses to each spark plug in sequence
DISTRIBUTOR
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Magneto
What is the function of a distributor
DELIVER ELECTRICAL PULSES to SPARK PLUGS
Ensures the pulses are delivered in the correct sequence
Pg 131
Magneto
What is the function of the rotor
PASS CURRENT to each SPARK PLUG
Rotor comes into contact with electrode associated to each spark plug
As the rotor turns wthin the distributor, it touches an electrode.
Each electrode is married up to each spark plug.
As the roto touches each electrode, the current passes to each spark plug
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Magneto
When does the spark occur in a spark plug
WHEN CONTACT BREAKER IS OPEN
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Magneto
The contact breaker and distributor rotor are driven by what
ENGINE via a SPINDLE
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Magneto
The engine drives a spindle which drives which 2 components
- CONTACT BREAKER
- DISTRIBUTOR ROTOR
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Magneto
The speed of the rotor and the contact breaker vary directly with what
ENGINE RPM
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Magneto
Each magneto is controlled by its own what
IGNITION SWITCH
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Magneto
How does the ignition switch work with regards to each magneto
ISOLATES IGNITION CIRCUIT
Each magnetos primary circuit is connected to earth
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Magneto
What is the name given to the ignition switch lead
“P” LEAD
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Magneto
If the ignition switch is closed, the circuit is LIVE or EARTHED
EARTHED
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Magneto
If the ignition switch is open, the circuit is LIVE or EARTHED
LIVE
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Magneto
What is the purpose of the ignition switch working in reverse to the normal standard of a switch i.e. open is live, closed is earthed
PROVIDE FAIL-SAFE PROTECTION
A break in the switches wiring would not cause the ignition system to fail. This would be important when in the air
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Magneto
Besides from providing a fail-safe element, what is an advantage of having 2 spark plugs per cylinder in terms of efficiency
ACCELERATOR COMBUSTION
Even burng spreads from both spark plugs simultaneously
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Magneto
What are the 2 elements of a pre-flight magneto check
- MAG DROP CHECK
- DEAD CUT CHECK
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Magneto
A mag drop check is conducted twice. The 1st test is conducted at around ____ RPM.
RPM should DROP or INCREASE and the engine should run SMOOTHLY or ROUGHLY
- 1200 RPM
- DROP
- SMOOTHLY
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Magneto
A mag drop check is conducted twice. The 2nd test is conducted at around ____ RPM.
RPM should DROP or INCREASE within specific limits and the engine should run SMOOTHLY or ROUGHLY
- 2000 RPM
- DROP
- SMOOTHLY
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Magneto
A successful check of the 1st mag drop check at 1200 RPM would prove what
ENGINE RUNNING on ONE MAGNETO
At a low RPM
At a low RPM, one magneto will still successfully be able to run the engine
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Magneto
A successful check of the 2nd mag drop check at 2000 RPM would prove what
ENGINE POWER not SIGNIFICANTLY EFFECTED
If one magneto were to fail, engine power would not be significantly effected
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Magneto
During the 2nd mag drop check at 2000 RPM, a complete dead cut would indicate what
IGNITION CIRCUIT FAILURE
Failure of one half of the ignition circuit
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Magneto
During the 2nd mag drop check at 2000 RPM, no drop in RPM would indicate what
IGNITION SYSTEM NOT EARTHED
One half of ignition system not earthed
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Magneto
During the 2nd mag drop check at 2000 RPM, a drop of 300-400 RPM and rough running engine would indicate what
MALFUNCTIONING SPARK PLUG
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Magneto
What must be carried out by a pilot before shutting down the engine
DEAD CUT CHECK
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Magneto
What are magnetos pressurised for high altitude operation
REDUCE RISK OF INTERNAL ARCHING
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Magneto
What is done to the magnetos for high altitude operation to help reduce the risk of internal arching
PRESSURISED
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Magneto
During start up, when the engine is turning slowly, what are 3 methods of assisting the system to ensure sufficient sparks are created to fire the engine
- Impulse Magneto
- High Tension Booster Coil
- Low Tension Booster Coil
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Magneto
How does an impulse magneto function
What component
SPRING LOADED CLUTCH
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Magneto
How does the high tension booster coil function
INDUCE LARGE CURRENT in 2nd WINDING
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Magneto
What does a trembler interrupter do in a high tension booster coil system
INTERRUPTS PRIMARY WINDING CIRCUIT
A trembler interrupter in the coil interrupts the primary winding circuit to produce a continous stream of high voltage impulses in the secondary (HT) circuit
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Magneto
The component used to interrupt the primary winding circuit in a high tension booster coil system is known as what
TREMBLER INTERRUPTER
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Magneto
A high tension booster coil system is know by what other name
SHOWER OF SPARKS
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Magneto
What component is connected to the primary winding in a low tension booster coil system
BATTERY
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Magneto
What is the purpose of a second set of contact breakers in a low tension booster coil system
SUFFICIENTLY RETARDED SPARK
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Magneto
How is a suficciently retarded spark ensured in a low tension booster coil system
CONTACT BREAKERS
2nd set of contact breakers
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How many volts are supplied to each spark plug
30,000 V
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What are the potential risks with a spark plug if the gaps between the electrodes are not correct
1. To small
2. To large
- Weak Spark
- No Spark
Pg 136
Spark plug fouling can occur when which 3 deposits block the gap in electrodes
- Oil
- Carbon
- Lead
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