Powerplant - Ignition Systems Flashcards
What is a magneto?
A special type of engine driven AC generator that uses a permanent magnet as a source of energy. The magneto develops a high voltage that is used to fire the spark plugs.
Where is the E-gap position in a magneto?
A few degrees past the neutral position
What is the piston position when the spark occurs in a cylinder?
A few degrees before top dead center of the compression stroke
What is a duel magneto ignition system?
Two magnetos in one housing, with one rotating magnet and cam, common to two sets of breakers points and coils.
When the ignition is in the OFF position, what is the condition of the primary?
It is completed through the ignition switch to the ground
In a dual magneto ignition system, what part of the system is grounded when the ignition switch is placed in the RIGHT position?
The left magneto circuit will be grounded
What is internal timing of the magneto?
Adjusting the breaker points to open when the rotating magnet is at the E-gap position
What is the purpose of an impulse coupling used with a magneto?
To spin the magneto rapidly to produce a hot spark for starting the engine and at the same time, retard the timing of the next spark
What is staggered timing ignition?
The firing of one spark plug before the other, instead of firing them simultaneously
What type of ignition system is used in most turbine engines?
An electronic capacitor type ignition system
When are turbine engine ignition systems normally in use?
For starting and restarting an engine only
What are two types of igniter plugs?
annular gap and constrained
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 are the three major circuits of a high tension magneto system?
The magneto circuit, primary electrical circuit, and secondary electrical circuit
What are the components of a high tension magnetic circuit?
A permanent rotating magnet, soft iron core, and pole shoes
What is the piston position when the spark occurs in a cylinder?
The piston is a specified number of degrees before top dead center on the compression stroke
What is 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 cylinders that spark plugs are installed in?
Because spark plugs can provide a lot of information about the health of a specific cylinder
What is the function of the igniter plugs in a turbine engine?
To provide a discharge gap for the current, which is stored in the capacitor. The discharge results in a high intensity spark which ignites the fuel-air mixture
How can you tell if a starter commutator is dirty or worn?
An excessively noisy starter
What does it mean when the starter relay clicks when the starter switch is placed in the “start” position?
The 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 the extremely high rates of electrical discharge in the turbine ignitors
What are the three parts of an ignition systems of a turbine?
Exciter, Ignition lead, and Ignitor
