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37 Cards in this Set

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  • Back
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
Commutator & Brushes should be inspected for wear beyond operational limits
Between field and Armature windings in starter generators, which ordinarily receive current 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
1. A ground power unit (GPU)
2. An onboard auxiliary power unit (APU)
3. Compressed bleed air from an already running engine
When should ignition ideally occur
A specific number of degrees as (determined by the manufacturer) before the piston reaches top dead center on the compression stroke
Why are Dual magnetos used in the engine ignition system
1. To improve combustion efficiency
2. to provide redundancy for safety
Why is magneto timing so important
For an engine to run properly, the spark plug in a cylinder has to fire at a specific time.

To produce the required energy for the spark at the required time, the magneto must be in the E-gap position, the breaker points must start to open, and the distributor must be electrically aligned with the particular cylinder.

If any of these requirements are not correctly adjusted, the engine will run rough or may not run at all.

When preparing a magneto for installation, first the internal timing must be correctly adjusted then the magneto-to-engine timing is adjusted
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
1. Permanent multipole rotating magnet
2. Soft iron core
3. Pole shoes
Name the three main circuits of a high tension magneto system
1. Magnetic
2. Primary
3. Secondary
What is an E gap angle
It is 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 Egap position the primary points open, which interrupts the current flow in the primary circuit 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 magnetos are grounded. When the ignition switch is turned to the "left" position, the right magneto is grounded, so that only the left magneto operates, and vice versa
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, and indicates the exact instant the magneto points open
Why are turbine engine igniters generally not susceptible to carbon fowling
Because 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 ignition system for a given amount of time, and is then followed by a minimum specified cooling down period
What are the three main components of a turbine engine ignition system
1. Ignition exciters
2. High tension leads
3. Igniters
When the engine is operating what does an ammeter/loadmeter indicate when connected to:
1. battery positive lead
2. generator output lead
1. When connected to the battery positive lead the ammeter indicates whether the battery is charging or discharging

2. When connected to the generator output lead 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 and 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
1. Constant speed drives
2. Integrated drive generators
3. Variable speed constant frequency (VSCF) power systems
Name the major parts of a DC motor
1. Armature
2. Field
3. Brushes
4. Frame assembly
Name the components of a direct cranking electric starter system
1. An electric motor
2. Reduction gears
3. An automatic engaging & disengaging mechanism
Name 3 types of DC motors
1. Series
2. Shunt
3. Compound
What type of DC motor is commonly used for a reciprocating engine starter and why
A series wound motor is commonly used 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 wiring used in US manufactured aircraft
The American wire gauge AWG
How are wire sizes represented
By a number gauged size. The smaller wires are represented by larger numbers. The smallest size wire normally used in aircraft is 22 gauge
What is the maximum slack allowed between the supports of a single wire or bundle installation
Not over 1/2 inch
Why are wires bonded on power plant installations
To provide a current return path for electrical assessories and to prevent static discharge