PWR SWITCH LIGHT ( alternate action )

PUSH - arms APU start circuits and opens the APU fuel valve, APU FUEL VALVE OPEN light (green) shown on the APU fire protection panel.

• only arms if airplane on ground, no fire detected, and EXTG switch not selected

RUN segment (green)

• APU is at operating speed after the START switch light is pushed.

PUSH - RUN segment (out)

• closes APU fuel valve, APU FUEL VALVE CLOSED light (white) shown on the APU fire protection panel, and the APU stops

FAIL - a failure is detected and the APU automatically stops.

START SWITCH LIGHT ( alternate action )

PUSH - STARTER segment (amber)

• starts automatic APU start sequence

STARTER segment (out)

• APU start sequence complete or stopped

GEN SWITCH LIGHT (alternate action)

PUSH - ON segment (green)

• APU starter-generator is supplying DC power

PUSH - ON segment (out)

• selects APU generator offline

WARN segment (amber)

• APU starter-generator offline with APU running

BL AIR SWITCH LIGHT ( alternate action )

PUSH - OPEN segment (green)

• APU bleed air valve open
• APU bleed air supplies air to the ECS if engine bleed air is off

PUSH - OPEN segment (out)

• APU bleed air valve is closed
• selects APU bleed air off

GEN OHT ADVISORY LIGHT

GEN OHT segment (amber) APU starter-generator overheat condition APU automatically shuts down