Air Systems Flashcards
Compartment Temp INOP light
- fault in zone temp controller
- compartment temp control OFF
- TRIM AIR switch OFF
- Zone overheat
- FWD and AFT INOP with Cargo Fire switch
Compartment Temp range
65°F (18°C) and 85°F (30°C)
Equipment Cooling SMOKE light
- Smoke is detected in the flight deck equipment cooling ducts
- System is automatically configured to evacuate smoke
CABIN ALTITUDE light and EICAS
- Cabin altitude exceeds 10,000 feet; or
14,650’ with High Altitude Landing selected (RR) - Illuminates the crew lavatory Cabin Depressurization Warning Light
-extinguishes when cabin alt is below 8500 feet
ENGINE HIGH STAGE light (757)
• Engine bleed system pressure is excessive
• Engine high pressure bleed air valve is automatically locked closed
- can only be unlocked on the ground by MX
How many temp zones
3 temperature zones: the flight deck and two cabin zones
What determines Pack output temp when pack controller in STBY mode?
Position of pack selector:
- N (normal) - Constant, moderate temperature (40°F inflight)
- W (warm) - Full warm
How is air distributed through the cabin and flight deck?
- Conditioned air from the packs flows into a mix manifold where it mixes with air from the recirculation fan ——> to cabin
- left and right pack output is joined prior to the mix manifold and provides 100% fresh conditioned air ——> flight deck
- recirculation fan draws air through the forward E/E system and returns it to the mix manifold
How is temp controlled with loss of trim air system?
- the packs attempt to maintain all compartments at an average temperature (75°F)
How are FWD equipment racks cooled?
- supply fans that draws cooling air from the cabin and forces it through the equipment racks and avionics
- differential pressure is low, the overboard exhaust valve automatically opens
Equipment OVHT light illuminates
- insufficient cooling airflow
- Overboard exhaust valve does not open when the recirculation fan fails
- Forward Equipment SMOKE light remains illuminated longer than five minutes
- Both aft equipment cooling exhaust fans are inoperative
Smoke detected in equipment cooling system
- SMOKE illuminates
- Operating supply fan is turned off
- Recirculation fan turns off
- One or both air conditioning packs switch to high flow
- Overboard exhaust valve opens
- OVHT light is inhibited for five minutes
How is Aft equipment cooled?
- continuously operating exhaust fans (2) that draws air through the equipment and exhausts it near the outflow valve
- one fan operated and the other in standby
Automatic Pressurizations modes
In AUTO 1 or AUTO 2:
- systems arms when doors closed and T/O thrust set
Takeoff Mode:
- pressurized to slightly below airport elevation
- outflow valve partially open
- outflow valve closes slightly on takeoff
Climb Mode:
- Max diff pres 8.6 psi at 35,000’
Cruise Mode:
- entered when constant altitude for 1 min
Descent Mode
- when aircraft descents more than 1000’
Landing and Ground Test mode:
- cabin altitude descents to slightly below field elevation (approx 100’ below)
- self test begins after landing
CABIN AUTO INOP
- AUTO 1 and AUTO 2 inoperative, or
- Cabin Altitude selector in MAN
What causes outflow valves to automatically close?
- aneroid switches automatically close outflow valves if cabin altitude exceed 11,000’
- normal operation of outflow valves restored when cabin altitude descends below 9,500’
What happens to the packs and cabin air distribution when Cargo Fire switch is set to DEPR
- one pack to low flow
- one pack shutoff
- conditioned air to cabin is shut off
- all conditioned air diverted to flight deck
What is bleed air used for?
- Air conditioning
- Pressurization
- Engine start
- Wing and engine anti-ice
- Hydraulic reservoir pressurization
- Cargo heat (767)
- Center hydraulic system Air Demand Pump (767)
- Engine thrust reversers (767)
Sources of engine bleed air
Low Pressure (LP) compressor - used during high power settings
High Pressure (HP) compressor - used during descent and low power settings
L or R ENG HI STAGE EICAS message (757)
- engine bleed air pressure excessive
- high pressure bleed air valve automatically locks close
- maintenance action required to unlock
What altitude can APU bleed air be used up to?
17,000’
What happens to the APU Bleed Valve after engine start?
APU Bleed valve will automatically close depending on the relative position of the engine bleed valves and the isolation valve.
How many external ground pneumatic connections
Two - 1 on the left duct and 1 on the right duct (757)
- both on left duct (767)
BLEED ISLN VAL EICAS message
isolation valve position disagrees with the commanded position