Chap 8 Flashcards
What component of a starter generator require periodic inspection?
Both commutator and brushes should be inspected for wear beyond operational limits
How can the remaining service life of starter generator brushes be determined
By visually inspecting the amount of wear groove remaining on the brushes
Between field and Armature winding in Starter generator, which ordinarily receive current for operation in the start mold?
Generally, both field and armature received current for operation into start mode
What are possible sources of low pressure compressed air used for starting jet transport aircraft equipped with air turbine starter?
A GPU, an APU , or air from another already running engene
When should ignition ideally occurs?
A specific number of degrees, before piston reaches TDC on the compression stroke
Why are dual magnetos used on engine ignition system?
To improve combustion efficiency and provide redundancy for safety
Why are magneto timing so important?
If not timed properly engine may run rough or may not run at all. First internal timing and then 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
Magnetic,primary and secondary
What is an E-gap angle?
It’s a point a few degrees beyond the neutral position of a rotating magnetic where maximum magnetic 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 rotating cycle, at the E-gap position, the primary point open, inducing a high voltage in the secondary coil
What is a P-lead and how does it function?
The p-lead connects the ignition switch to the primary circuit of the magneto. When ignition switch is off, the p-leads on both mags are grounded.
What’s a magneto timing light used for and what does it indicates?
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 not susceptible to Carbon fouling?
Because the high energy spark cleans off any deposited on the firing end
What’s the function of a duty cycle in relation to a turbine engine ignition system?
It 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?
Ignition exciters, high tension leads, igniters
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 voltage of a DC generator controlled?
By varying the field current strength
What is the most common type of alternator use the most aircraft AC systems?
The three-phase alternator
How does a voltage regulator controls the voltage of an alternator?
By regulating the voltage outputs 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 torbofan engines?
Constant speed drives, integrated drive generator and variable speed constant frequency power systems
Name the major parts of a DC motor
The Armature, field, brushes and frame assembly
Name the components of a direct cranking electric starter system
An electric motor, reduction gears, and an automatic engaging and disengaging mechanism
Name three types of DC motors
Series, shunt and compound
What type of DC motor is commonly used for the reciprocating engine started and why?
He 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 engines running
What is a possible indication when a starter drags?
Hey dirty or worn starter commutator
Where would wire with high-temperature insulation material be used?
When they run closed to high-temperature areas such as exhaust stacks or heating ducts
What is the size standard for electrical wire using US manufactured aircraft?
The American wire gauge(AWG)
How are wires sizes represented?
By a numbered gauge size. The smaller wire are represented by larger numbers. The smaller 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 wire bonded on power plant installations?
To provide a current return path for electrical accessories , and to prevent static discharge
