Ignition and Starting Systems Flashcards
Name one general type of inertia starter.
Electric
What is a magneto?
Self-contained AC generator driven by the engine for the purpose of ignition
Why are magneto ignition systems preferred over battery type ignition systems for reciprocating engines?
Magnetos are an independent ignition source and do not rely on battery power to provide ignition
What can cause a reciprocating engine to continue to run when the ignition switch is in the OFF position?
A break in the p-lead wire from the magneto to the switch
What is the purpose of the condenser in a high-tension magneto electrical system?
To prevent arcing at the points and to hasten the collapse of the magnetic field around the primary coil
What does a capacitor do in a magneto circuit?
Prevents arcing and hastens the collapse of the magnetic field about the primary coil
Where is the E-gap position?
When the poles of the rotating magnet are a few degrees past the neutral position when the points begin to open
What are the three major circuits of a high-tension magneto system?
Magnetic and Primary and Secondary Electrical
What are the components of a high-tension magnetic circuit?
Permanent rotating magnet, soft iron core, and pole shoes
What happens when the primary breaker points open in a magneto?
Stops the flow of current in the primary coil
What is the position when the spark occurs in a cylinder?
A specified number of degrees before top dead center on the compression stroke
What is a dual magneto?
Two magnetos in one housing that share the rotating magnet and cam
What is the difference between a low tension and a high-tension ignition system?
In a High-Tension System, high voltage is generated in the magneto and flows to the plugs through high tension leads. In Low-Tension Systems, the low voltage is generated in the magneto and flows through the low tension leads
When the ignition switch is in the OFF position, what is the condition of the primary circuit?
It is completed through the ignition switch to ground
What three conditions are required to fire plugs in a cylinder when the piston is in the prescribed position?
The magneto’s magnet poles must be in the E-gap position, the breaker points must open, and the distributor rotor must be aligned with a distributor electrode for that cylinder.
What is a dual ignition system and what part of the system is grounded when the ignition switch is placed in the RIGHT position?
A dual ignition system uses two separate magnetos with the harness arranged so that each magneto fires one plug in each cylinder. If the switch is set to RIGHT, the left magneto will be grounded, preventing it from firing.
What is internal timing of a magneto?
Adjusting the breaker points to open when the poles of the rotating magnet are at the E-gap position
What is the purpose of an impulse coupling used with a magneto?
To retard the timing of the spark to after top dead center for starting the engine
What is staggered ignition timing?
Firing of one spark plug before the other
What is the proper spark plug reach?
When the electrode end of the plug inside the cylinder is in the best position to achieve ignition
Why is it important to keep track of the cylinder that spark plugs are installed in?
Spark plugs can provide a lot of information about the health of a specific cylinder
What type of ignition system is used in most turbine engines?
Electronic Capacitor Type
What is the function of the ignitor plugs in a turbine engine?
Provide a discharge gap for current, which is stored in the capacitor
When are turbine engine ignition systems normally in use?
Only for starting or restarting an engine
What are two types of ignitor plugs?
Annular gap - long reach, Constrained gap - short reach
What is the purpose of the dual magneto configuration?
Redundancy and safety
How can you tell if a starter commutator is dirty or worn?
Excessively noisy starter
What does it mean when the starter relay clicks when the starter switch is placed in the START position?
Supply voltage is too low to supply enough current to the relay coil to fully engage the contact points
What is an advantage of air-turbine starters when compared to electric starters for large turbine engines?
They are light weight and do not have the same cool down periods as electric starters
Why do turbine ignitors not get carbon fouled as often as reciprocating engine spark plugs?
Due to extremely high rates of electrical discharge in the turbine ignitors
What are three parts of an ignition systems of a turbine?
Exciter, Ignition Lead, Ignitor
What is the difference between a temporary magnet and a permanent magnet?
A permanent magnet retains its magnetic properties for a long period of time. Temporary magnets act like permanent magnets when they are within a strong magnetic field
What does the ignition light indicate when timing a magneto?
When the points are beginning to open
In terms of the engine crankshaft position, when does the ignition event occur?
A specified number of crankshaft degrees before top dead center on the compression stroke
What is the purpose of the capacitor in a magneto?
It prevents arcing at the points and aids in the collapsing of the magnetic field
What is the main concern when preparing a magneto for installation?
Internal timing
What are the three events required to fire a spark plug in a cylinder when its piston is in the prescribed position?
Magneto in E-gap position, Breaker points opening, Distributor electrically aligned with that cylinder
What is the function of a duty cycle in relation to 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
Name 3 sources of high volume, low pressure compressed air commonly used for starting jet transport aircraft equipped with air turbine starters.
APU, GPU, Compressed Bleed Air
Name two parts of a starter generator that commonly require periodic inspection to ensure that they do not wear beyond operational limits.
Commutator and brushes
Between the field and armature windings in starter generator, which ordinarily receive current from operation in the start mode?
Both the field and the armature
What are the three components of a spark plug?
Electrode, Insulator, Bore
Spark plug leads perform 2 functions; what are those functions?
Carry the voltage and shield the power from radios.
