Electrical, Starting, + Ignition Systems Flashcards
How can the remaining service life of 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?
Both commutator and brushes should be inspected for wear beyond operational limits.
Between field and armature windings in starter generators, which ordinarily receive currents for operation in the start mode?
Generally, both field and armature receive current for operation in the start mode.
What are possible sources of low pressure compressed air, used for starting jet transport aircraft equipped with air turbine starters?
Ground power unit.
Onboard auxiliary power unit.
Compressed bleed air from an already running engine.
When should ignition ideally occur in a reciprocating engine?
A specific number of degrees before the piston reaches top dead center on the compression stroke.
Why are dual magnetos used in the engine ignition system?
Improve combustion efficiency.
Provide redundancy for safety.
Why is magneto timing so important?
The spark provided by the magneto must fire at a specific time for an engine to run properly.
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:
A permanent multi-pole rotating magnet.
Soft iron core.
Pole shoes.
Name the three circuits of a high tension magneto system:
Magnet.
Primary.
Secondary.
What is a E gap angle?
A point a few degrees beyond the neutral position of a rotating magnet where maximum magnetic field stress exists.
What reduces arcing 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?
In 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 circuits causing a high rate of flux change in the core, and inducing a pulse of high voltage in the secondary coil.
What is the P lead and how does it function?
The P lead connects the ignition switch to the primary circuit of the magneto. When the ignition switch is turned off the P leads on both magneto’s are grounded.
What is a magneto timing light used for and what does it indicate?
It is used for both internal magneto timing and magneto to engine timing.
It indicates the exact instant the magneto points open.
Why are turbine engine igniters generally not susceptible to carbon fouling?
The high energy sparks they produce, clean off any deposits on the firing end.
What is the function of a duty cycle in relation to a turbine engine ignition system?
A duty cycle allows the operation of the engine system for a given amount of time, and it is then followed by a minimum specified cooling down period.
What are the three main components of a turbine engine ignition system?
Ignition exciters.
High tension leads.
Igniters.
When the engine is operating, what does an ammeter or load meter indicate when connected to:
1) a battery positive lead?
2) generator output lead?
1) the ammeter indicates whether the battery is charging or discharging.
2) it indicates the current produced by the generator or electrical system load.
What is done to ensure that each generator shares the load in a multiple generator system?
The generators are paralleled.
Where would you find generator rating and performance data?
On the data plate attached to the generator.
How is the voltage of a DC generator controlled?
By varying the field current strength.
What is the most common type of alternator used in most aircraft AC systems?
The three phase alternator
How does a voltage regulator control the voltage of an alternator?
By regulating the voltage output of the DC exciter.
What does the speed of rotation in number of poles of an alternator determine?
The frequency of the alternator output
What are some of the methods used to maintain 400 Hz alternator output frequency on large turbojet or turbofan engines?
Constant speed drives.
Integrated drive generators.
Variable speed constant frequency power systems.
Name the major parts of a DC motor:
Armature.
Field.
Brushes.
Frame assembly.
Name the components of a direct cranking electric starter system:
Electric motor.
Reduction gears.
Automatic engaging and disengaging mechanism.
Name three types of DC motors:
Series.
Shunt.
Compound.
What type of DC motor is commonly used for a reciprocating engine starter and why?
A series wound motor.
Because it has a high starting torque under heavy load conditions.
What are the operating modes of a turbine engine starter generator?
It operates first as a starter, then as a generator once the engine is running.
What is a possible indication when a starter drags?
A dirty or worn starter commutator.
Where would wire with high temperature insulation material be used? 
When they run close to high temperature areas, such as exhaust stacks or heating ducts.
What is the size standard for electrical wire used in US manufactured aircraft?
The American wire gauge (AWG)
How are wire sizes represented?
By a numbered gauge size. Smaller wires are represented by larger numbers.
What is the maximum slack allowed between the supports of a single wire or bundle installation?
Not over a half inch.
Why are wires bonded on power plant installations?
To provide a current return path for electrical accessories, and to prevent static discharge.
