APU

Question 1

APU selector switch - OFF

Answer 1

• Closes APU bleed air valve, if open
• Initiates APU cooling cycle
• Closes APU fuel valve and inlet door shutting down APU when cooling cycle is complete
• Resets auto shutdown fault logic

Question 2

APU selector switch - ON

Answer 2

Normal operating position

• Opens APU fuel valve and inlet door
• Activates AC or DC fuel pump
• Powers APU controller
• Permits APU bleed valve to open if APU Bleed Switch is on when APU reaches operating speed

Question 3

Maximum APU operating altitude

Answer 3

Up to airplane maximum certified altitude

Question 4

APU bleed air altitude

Answer 4

Available up to approximateyl 17,000’

Question 5

APU fuel pump

Answer 5

Fuel provided from left manifold. DC pump is no AC power is available. When AC power is available, left forward AC pump is used regardless of switch position.