Ignition And Starting

Question 1

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

Answer 1

By visually inspecting 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 field and armature windings in starter-generators which ordinarily receive current for operation in the start mode?

Answer 3

BOTH… field and armature.

Question 4

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

Answer 4

GPU and APU

Question 5

When should ignition ideally occur (Recip)

Answer 5

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

Question 6

Why are dual magnetos used in the engine ignition system?

Answer 6

To improve combustion efficiency and provide redundancy for safety.

Question 7

Why is magneto internal timming so important?

Answer 7

For the engine 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: (Magnetic Circuit)

Answer 10

A permanent multipole rotor magnet, soft iron core and pole shoes.

Question 11

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

Answer 11

Magnetic, primary and secondary.

Question 12

What is an E-gap angle?

Answer 12

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

Question 13

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

Answer 13

A capacitor.

Question 14

How does a magneto produce the 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 floow 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.

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 its piston is in the prescribed position?

Answer 17

Magneto in E-GAP position, breaker points opening, and the distributor electrically aligned with that cylinder.

Question 18

What is the P-LEAD and how does it function?

Answer 18

It connects the ignition switch to the primary circuit of the magneto.
When the ignition switch is turned off, the P-LEADS of both magnetos are grounded. When the ignition switch is turned to the LEFT position,
the RIGHT magneto is grounded and vise-versa.

Question 19

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

Answer 19

Internal magneto timing and magneto-to-engine timing, indicates the EXACT MOMENT the magneto points 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 on 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 a minimum specified cooling down period.

Question 22

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

Answer 22

Ignition exciters, hight tension leads and igniters.