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
L or R BLD DUCT LEAK
- high temperature bleed air leak is detected
- disappears when temperature along the duct has cooled
L or R ENGINE BLEED VAL/OVHT
- engine bleed air temperature is excessive
- Engine bleed air valve close (PRSOV)
- HP bleed valve automatically close (757)
- HPSOV, PRV are closed (767)
- system can be reset by selecting switch OFF then ON
When is pack high flow inhibited (767)
- Wing anti-ice on and only one bleed source available
- Flaps are not in the UP position
- An engine is shutdown
- Cargo Fire switch to DEPR
Equipment Cooling OVRD (767)
- Opens smoke override valve and positions equipment cooling system for reverse airflow
- Shuts down nitrogen generation system (as installed)
Automatically selected:
− Jettisoning fuel during single-engine operations – or –
− When Cargo Fire switch is pushed
FWD E/E config on the ground, packs OFF, temp below 45ºF
- closed loop
- supply fan ON
- exhaust fan ON
- OVBD (smoke and exhaust) valve CLOSED
FWD E/E config on the ground, packs OFF, temp above 45ºF
- open loop
- supply fan ON
- exhaust fan ON
- OVBD Exhaust valve Open
- SMOKE OVBD valve Closed
- BYPASS shutoff valve Closed
FWD E/E config on the ground, engine ON
- closed loop
- Supply and Exhaust Fans ON
- OVBD valves CLOSED
How is Cargo Heat normally supplied (767)
- FWD and AFT by bleed air system
- automatically maintains temp above 45ºF (7ºC)
Systems supplies by center pneumatic duct (767)
- Center hydraulic reservoir
- Aft cargo heat
- Center hydraulic system ADP
- Smoke detectors
Systems supplied by left pneumatic duct (767)
- respective thrust reverser
- respective nacelle anti-ice
- respective hydraulic reservoir
- respective pack
- respective wing anti-ice
Systems supplied by right pneumatic duct (767)
- respective thrust reverser
- respective nacelle anti-ice
- respective hydraulic reservoir
- respective pack
- respective wing anti-ice
- FWD cargo heat
What happens if BODY DUCK LEAK or R/L BLD DUCK LEAK EICAS messages remain illuminated after the bleed source is turned off (767)
leak exists between the left and right isolation valves in the common manifold
What happens if a L or R BLD OVHT/OVHT light occurs? (767)
- respective engine bleed valve automatically closes
- HPSOV and PRV close
- PRV will open if engine anti-ice is activated
- Thrust Reverse not avail
How many Pos/Neg Pressure Relief valves
757:
2 x Pos PRV aft of left wing
2 x Neg PRV right of FWD cargo door 1
767:
2 x Pos PRV FWD of left LE
4 x Neg PRV (2 on AFT cargo door, 2 on FWD cargo door)
Auto Rate selector
- sets limit of cabin altitude rate of climb or descent
- index mark is normal position (500 fpm climb, 300 fpm descent)
How is outflow valve controlled?
- actuator geared to 3 motors (only one operative at a time)
- 2 AC motors (APC 1 and APC 2)
- 1 DC motor (manual
How many Ext air connections?
PW:
- 2 (one to left duct and one to right duct)
RR:
- 3 (2 to left duct and one to right duct)
GE:
- 2 (both to left duct)
APU Bleed valve logic in flight
APU ON and APU bleed switch ON
APU Bleed Valve opens if:
- Left Bleed and ISO valve closed, or
- Both Eng Bleed Valves closed and ISO valve open
- APU air shuts off at 23,000’
- APU air restored at 20,000’
APU VALVE light/APU BLEED VAL EICAS
Disagreement with valve position
When does the HPSOV open or close
- Opens: To ensure sufficient air pressure to system at lower thrust settings
- Closes: As thrust increases and Low Pressure (LP) check valve provides enough air to system
How many ground air connections required for start?
- (B767) Two connections are required
− (B757) Two connections are recommended
− (RR) Three connections may be required in extremely cold weather
DUCK LEAK discrete light
− Bleed air leak in:
♦ Wing – or –
♦ Body – or –
♦ Engine strut
L or R Pack Temp Advisory
Pack controller fault – or –
♦ Temperature valve freezes in position – and –
♦ Pack cannot be reset – and –
♦ Pack must be operated in STBY
Pack overheat
♦ Temperature valve driven full cold, if due to outlet over-temperature – and –
♦ Pack can be reset after cooling
What determines the configuration of Equipment Cooling
• On ground, system configuration determined by:
- Engine operation – and –
- Pack operation – and –
- Aircraft skin temperature – and –
- Ambient temperature
• In flight:
- Only one fan operates at a time – and –
- Air is constantly recirculated
Normal Cabin Differential Pressure
8.6 PSI
When is Pack High Flow inhibited (767)
- Wing anti-ice on and only one bleed source available
- Flaps are not in the UP position
- An engine is shutdown
- Cargo Fire switch to DEPR
