APU

Question 1

What is the brain of the APU?

Answer 1

ESU: Electronic Sequence Unit

DESU: Digital Electronic Sequence Unit (5 BITE windows)

Question 2

APU Percentages

Answer 2

5%= Start fuel, igniter

14%= Main fuel, event counter, hour meter starts

70%= start fuel stops, ignighter stops, start valve closes

90%= max fuel, 1.5-3.5 sec later APU ON indication

Question 3

DESU

Answer 3

5 BITE windows

Start, Main, Max fuel

Question 4

APU Fire T handle

Answer 4

Shuts off fuel to APU

Question 5

What are the two modes that the ESU operates in?

Answer 5

Start sequence mode, operational mode

Question 6

How to ID Garrett vs Turbomach APU

Answer 6

Garrett: Blue APU top and ESU, 1 fuel solenoid

Turbomach: metal color, oil filler neck, 3 fuel solenoid

Question 7

APU olil sampling interval

Answer 7

360 hours or 12 months

Question 8

What are the major components of the APU?

Answer 8

The major components of the APU:

gas turbine power section

reduction gear drive

appropriate controls and accessories.

Question 9

What must be removed to visually check the ESU BITE indicators?

Answer 9

The soundproofing panel from cabin ceiling must be opened in order to visually check the ESU BITE indicators.

Question 10

How is the APU accumulator recharged?

Answer 10

The APU is recharged by placing GENERATORS APU switch to ON and visually checking accumulator for proper charge (pressure gage and tape indicator) or by the hand pump.