Air Conditioning Temperature Control

Question 1

ZONE TEMP lights (amber)

2

Answer 1

• illumination of the CONT CAB ZONE TEMP indicates a duct temp overheat or failure of the flight deck primary and standby temperature control (dual failure)
• a failure of the primary or standby flight compartment temperature control or a malfunction in the system causes the CONT CAB ZONE TEMP light and AIR COND annunciator to come on only when the MASTER CAUTION system is recalled
• illumination of the FWD CAB or AFT CAB ZONE TEMP indicates duct temp overheat
• associated trim air modulating valve closes and cold air then flows through the duct to cool it
• FWD CAB or AFT CAB and AIR COND annunciator illuminate after a MASTER CAUTION recall if the associated zone temp control has failed
• if lights extinguish when MASTER CAUTION is reset, dispatch is permitted
• select a cooler temp for the zone and press the trip reset button
• if the duct temperature increases rapidly, turn the trim air off as a pack trip will occur

Question 2

TEMPERATURE SELECTORS

CONT CAB, FWD CAB and AFT CAB

Answer 2

AUTO
- automatic temp control for the associated zones to approximately 70°F / 21°C
- rotate toward C (cool) or W (warm) to set the temp (65°F - 85°F / 18°C - 30°C)
- failure of a temp selector will cause default to a 75°F / 24°C set point
OFF
- closes the associated trim air modulating valve
- any individual zone switched off
- temp selector setting will be ignored by the temperature contol system

Question 3

TRIM AIR switch

Answer 3

ON
- trim air pressure regulating and shutoff valve signaled open
- allows bleed air from upstream of the packs to be directed to the three trim air modulating valves
OFF
- trim air pressure regulating and shutoff valve signaled closed
- the three zone trim air systems are mechanically and electrically disabled
- left and / or right electronic controllers will control both packs independently
- the left pack will provide air in response to the CONT CAB selector to establish the temp for the flight deck
- the right pack will average the demands of the FWD and AFT zones