Ignition and Starting Systems

Question 1

How can the remaining service life of starter generator brushes be determined?

Answer 1

By visually inspecting in the amount of wear groove remaining on the brushes.

Question 2

What components of the starter generator require periodic inspection?

Answer 2

Both commutator and brushes should be inspected for wear beyond limits

Question 3

Between the field and armature, windings and starter generators, which ordinarily receive current for operation in the start mode

Answer 3

Both the field and armature

Question 4

What are possible sources of low pressure compressed air use for starting jet transport aircraft equipped with air turbine starters?

Answer 4

GPU and APU

Question 5

When should ignition ideally occur?

Answer 5

A specific number of degrees before the piston reaches the top dead center of the compression stroke

Question 6

Why are dual magnetos used in the engine ignition system?

Answer 6

To prove combustion efficiency and provide redundancy for safety

Question 7

Why is magneto internal timing so important?

Answer 7

For the engine to run properly

Question 8

What is the main concern when preparing a magneto for installation?

Answer 8

Internal timing

Question 9

What function does a magneto perform?

Answer 9

It produces a high voltage that forces a spark to arc across a spark plug gap

Question 10

Name the components of a high tension magneto system

Answer 10

A permanent multipole rotor magnet with soft iron core and pole shoes

Question 11

What is a E gap angle?

Answer 11

It is a point a few degrees beyond the neutral position where maximum magnetic field stress exists

Question 12

Name the three main circuits of a high tension magneto system?

Answer 12

Magnetic, primary, and secondary

Question 13

What reduces arcing in the points and also aids the collapsing of the magnetic field in a magneto

Answer 13

Capacitor

Question 14

How does a magneto produce a high-voltage required to fire a spark plug?

Answer 14

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 circuit, causing a high rate of flux change in the core and inducing a pulse of high voltage in a secondary coil

Question 15

When an ignition switch is off in a magneto system? What is the condition of the ground circuit?

Answer 15

The circuit to ground is completed

Question 16

Which magneto is grounded when the magneto switch is selected to the right magneto?

Answer 16

The left magneto circuit

Question 17

What are the three events required to fire a spark plug in a cylinder when it’s piston is in the prescribed position?

Answer 17

Magneto in a E gap position, breaker points opening, and the distributor electrically aligned with that cylinder

Question 18

What is the P lead and how does a function?

Answer 18

It connects the ignition switch to the primary circuit to the magneto. When the ignition switch is turned off, the P-Leads of both magnets are grounded. When the ignition switch is turned to the left position, the right magneto is grounded and vice versa.

Question 19

Why is a magneto timing light used for what does it indicate?

Answer 19

Internal magneto timing and magneto to engine timing and indicates exact moment the magneto points are open

Question 20

Why are turbine engine igniters generally not susceptible to carbon fouling?

Answer 20

Because the high energy sparks they produce clean off any deposits of the firing end

Question 21

What is the function of a duty cycle in relation to a turbine engine ignition system?

Answer 21

A duty cycle allows the operation of the ignition system for a given amount of time, followed by minimum specified cooldown period.

Question 22

What are the three main components of a turbine engine ignition system?

Answer 22

Ignition exciters, high tension leads, and igniters