Ignition and starting systems Flashcards
How can the remaining service life of a starter generator brushes be determined?
By visually inspecting the amount of wear groove remaining on the brushes
What components of the starter generator require periodic inspection?
The commutator and brushes should be inspected for wear beyond limits
Between the field and armature windings in a starter generator, which ordinarily receives current for operation in the start mode?
Both the field and armature windings receive current
What are possible sources of low pressure compressed air that is used for starting jet transport aircraft equipped with air turbine starters?
Ground power unit (GPU)
Auxiliary power unit (APU)
When should ignition ideally occur?
At a specific number of degrees before the piston reaches the top dead center on the compression stroke
Why are dual magneto’s used in an engine ignition system?
To improve combustion efficiency and provide redundancy for safety
Why is magneto internal timing so important?
For the engine to run properly
What is the main concern when preparing a magneto for installation?
Internal timing
What function does a magneto perform?
It produces a high voltage that forces a spark to arc across a spark plug gap
Name the components of a high tension, magneto system:
Permanent multipole rotor magnet
Soft iron core
Pole shoes
Name the three main circuits of a high tension, magneto system
Magnetic
Primary electrical
Secondary electrical
What is an E gap angle?
It’s the point a few degrees beyond the neutral position where maximum magnetic field stress exists
What reduces arching in the points and also AIDS, the collapsing of the magnetic field in a magneto?
A capacitor
How does a magneto produce the high voltage required to fire a spark plug?
During the rotation cycle, when the magnetic rotor is in the E gap position the primary points open which interrupts the current flow in the primary circuit. This causes a high rate of flux change in the core and inducing a pulse of high voltage in the secondary coil.
When an ignition switch is off in a magneto system, what is the condition of the ground circuit?
The circuit to ground is completed
Which magneto is grounded when the magneto switch is selected to the right magneto?
The left magneto is grounded
What are the three events required to fire a spark plug in a cylinder when it’s piston is in the prescribed position?
Magneto must be in the E gap position
Breaker points must be opening
The distributor must be electrically aligned with that cylinder
What is the P lead and how does it function?
It connects the ignition switch to the primary circuit of the magneto. When the ignition switch is turned off, the P leads of both magneto’s are grounded when the ignition switch is turned to the LEFT position, the RIGHT magneto is grounded and vice versa
Why is a magneto timing light used and what does it indicate?
It is used for internal magneto timing and magneto to engine timing. It indicates the exact moment the magneto point opens
Why are the turbine engine igniter generally not susceptible to carbon fouling?
Because the high energy sparks they produce clean off any deposits
What is the function of a duty cycle in relation to a turbine engine ignition system?
A duty cycle allows operation of the ignition system for a given amount of time, followed by a specified cooling down period
What are the three main components of a turbine engine ignition system?
Ignition exciters
High tension leads
Igniters
