Air Conditioning Flashcards
Provides?
Air renewal, constant selected temp
Zones
Cockpit, fwd cabin, aft cabin
Supplied by pneumatic system via?
Two pack control valves
Two packs
Mixing unit (cabin and packs)
Ram air?
Ambient air to mixer in emergency
Temperature regulation by?
Zone controller and two pack controllers or two ACSC (AC system controller)
Temperature regulation
Hot air regulating valve, and trim air valves, tapped upstream of packs, mixed after mixer
FAP control (flight attendant panel)
+- 2.5 degrees
AC Controller 1, 2
1 controls cockpit
2 controls fwd cabin, aft cabin
Pack flow control valve
Pneumatically operated, electric control, spring loaded to close
Closes when: pack overheat, engine start, operation of fire switch
Emergency ram air
Ventilates in case of: smoke, fail of both packs
Won’t open if DP more than 1 psi
Hot air valve
Pneumatic operated, electrical control, spring closed
Closes if: Both ACSC fail, duct overheat, two trim air valves fail
Fails if duct temp reaches 88 degrees
Trim air valve
Electrically controlled
Cockpit, ACSC 1
Cabins, ACSC 2
Temp regulation
Temp selectors in cockpit, zone controller computes a temp demand, then fine tuned on the FAP
Range 18 - 30
Pack flow control
High flow auto for:
Single pack op, APU supply
Normal auto:
LO selected and temp demand not satisfied
Lane fail
One pack fails, the other takes over
Both, hot air valve closes, trim valves remain in current position
ACM (air cycle machine) in packs fail
ACSC regulates temp by turbine bypass valve and ram air
Pack flow reduced due ACM seizure
Pack engine start sequence
If cross bleed closed, valve on engine start side closes
Remains closed when: eng master set to on/start, start valve open, n2 less that 50%
Reopening delayed for 30 secs
Pack also closed for
Low pressure upstream
Compressor overheat
Fire pb
Ditching
Pack flow selector
Single pack, apu supply both high flow
If low, pack can auto norm if insufficient demand
