Pack Flow Selector
Permits selection of Pack Flow according to number of passengers and ambient conditions.

Zone Temperature Selectors
Adjust Temperature for associated Zone.

HOT AIR Switch

• ON - Automatically controls zone Hot Air pressure regulating valve.
• OFF - Closes Hot Air pressure regulating valve and trim air valves and resets fault circuit.
• Fault Light - Illuminates amber when duct overheat is detected. If this occurs, the zone Hot Air pressure regulating valve and trim air valves automatically close. The FAULT light stay on until ;power temperature is sensed with the switch off.

RAM AIR Switch (Guarded)

• ON - Illuminates when selected on. If the DITCHING switch is in its normal guarded position:
  • Ram Air inlet opens
  • Normal outflow valve control is maintained if differential pressure is greater than or equal to 1 psi
  • Outflow valve opens if differential pressure is less than 1 psi.
• OFF - Closes Ram Air inlet.

APU BLEED Switch

• ON - Opens APU Bleed valve provided N is greater than 95% and there is no leak on APU or left side Bleed.
• OFF - Closes APU valve.
• Fault Light - Illuminates amber when APU leak is detected.

X BLEED Selector

• AUTO - Opens crossbleed valve if APU Bleed valve is open; closes crossbleed valve if APU Bleed valve is closed or an air leak is detected.>
• OPEN - Opens crossbleed valve>
• SHUT - Closes crossbleed valve>

PACK 1/2 Switches

• ON - Automatically controls Pack Flow control valve. Valve regulates flow, except in the following conditions:
  • Upstream pressure is below minimum
  • Compressor outlet overheat
  • During Engine Start sequence with ENG MODE selector set to IGN/START or CRANK and:
    • Either ENG MASTER switch is ON
    • The start valve is open
    • N₂ is less than 50%
  • Corresponding fire switch is depressed
  • DITCHING switch is selected ON
• OFF - Closes Pack Flow control valve.
• Fault Light - Illuminates amber when Pack Flow control valve position disagrees with selected position, or if compressor outlet overheats

ENG BLEED 1/2 Switches

• ON - Opens Bleed valve provided:
  • Upstream pressure is above 8 psi
  • APU BLEED switch is OFF or APU Bleed valve is closed
  • There is no leak, over-pressure or over-temperature detected
  • ENG FIRE switch not released out
  • Engine start valve is closed
• OFF - Closes Bleed valve and HP valve. OFF light illuminates white.
• Fault Light - Illuminates amber to indicate:
  • Over-pressure downstream of Bleed valve
  • Bleed overheat
  • Wing or engine leak on associated side
  • Bleed valve not closed during Engine Start
  • Bleed valve not closed with APU Bleed ON