The Ignition System Flashcards
The Ignition System
Required to facilitate the combustion via a spark
Generates a very high voltage to produce a spark and ignite the mixture in the cylinder
The Magnetos
An electrical generator which supplies high voltage charges to the relevant spark plugs at the correct timing
Independent of the electrical system
A generator and transformer
Components of a Magneto
Rotating magnet A coil (primary coil) Contact breaker points A capacitor A distributor
The Workings of a Magneto
The magnet rotates, creating a magnetic flux, inducing a low voltage charge (current) in the primary coil
The secondary coil is a ‘step up transformer’ (many more windings) and converts the low voltage charge to a high voltage charge when the contact breaker points are open
The energy is then transferred via the distributor to the relevant spark plug at the correct timing, which is in the circuit of the secondary coil
The job of the capacitor is to absorb some of the energy from the coil which helps to extend the service life of the equipment
Condenser
Prevents the current from flowing when when the contact breaker points are open
Ignition Switch
When turned off the primary coil is earthed and the magneto is off
When the switch is on the magneto is live
Ignition Harness
Carries the current from the magneto to the spark plugs
Enclosed in a case that helps to prevent radio interference
Starting Aids
The starter motor cannot turn the crankshaft fast enough to create a spark
A means of overcoming this problem by providing a retarded spark
Impulse Coupling
Contains a spring which winds up the engine as it is cranked
When sufficient tension is present, the spring unwinds rand rapidly rotates the magneto rotor
Disengaged once the engine is running
Booster Coil
An alternative to an impulse coupling
A battery coil arrangement powered by the aircraft electrical system and supplying high voltage current direct to the distributor
Dual Ignition System
For redundancy two separate systems are provided
Two magnetos that drive separate spark plugs for each cylinder
Results in a more efficient combustion
The Starter Relay
Prevents high currents from connecting to the ignition switch in the cockpit
When the switch it turned to start a small current is created in the starter key circuit which operates the starter relay
A large current then activates the starter motor, which is connected to the battery
