Air Systems Flashcards
How many temperature zones?
7 temperature zones:
Passenger:
- flight deck
- upper deck
- main deck zones A - E
Freighter:
- flight deck
- upper deck
- crew rest
- fwd and aft main deck
- fwd and aft lower lobe cargo deck
How many packs and controllers?
- 3 identical packs
- 2 identical pack temperature controllers (PTCs) - A and B
*pack valves are controlled electrically by PTC and open via bleed air pressure
How many channels for each Pack Temperature Controller (PTC)
- 3 channels
- 1 channel for each pack
- PTCs alternate after touchdown or if a fault is detected
How many flow rates does each pack have?
Normal and High
- Normal flow during cruise reduces fuel consumption by approximately 0.3%
How is conditioned air distributed through the cabin?
Flow rate and operation determined by:
- phase of flight
- number of pack operations
- position of lower lobe cargo conditioned air flow rate selector (freight)
Trim Air Switch On
- master trim air valve open
- zone trim valves operate automatically
- system provides hot bleed air to the zone duct condition air through zone trim valves
- zone trim air valves modulated by ZTCs (zone trim controllers)
- trim air to the lower cargo lobe (FWD&AFT) not controlled by Master Trim Air Valve
How is the cargo compartment heated?
FWD Compartment:
- from heated air exhausted from the electrical and electronic (E and E) compartment
Aft Compartment:
- bleed air from center section of bleed air duct
- thermal switch opens and closes temperature control valve
How are flight deck equipment and electrical equipment cooled?
- internal fans and valves directed cool cabin air from lower fuselage into the equipment racks
- warm exhaust air is either:
- directed to the FWD Cargo compartment
- recirculated in a closed loop through the E and E compartment
- ducted overboard
- on the ground when ambient temps are moderate or high warm air is exhausted overboard
How is the cabin pressurized?
- 2 outflow valves in the rear of the cabin operate in parallel to regulate the discharge of conditioned cabin air
- 2 cabin controllers (A and B) control both outflow valves
What are the different modes during automatic operation of the pressurization system?
In Flight:
Climb mode - cabin altitude increases on a schedule determined by airplane climb rate and flight plan cruise altitude (from FMS)
* cabin altitude controller assumes 39,000’ if cruise altitude is not available from FMS
Cruise mode - controls cabin altitude to a maximum of 8,000’
Descent mode - entered at T/D or initial descent of 1,000’ from cruise; controls cabin altitude to slightly below planned landing altitude (from FMS or MAN selection)
* cabin altitude controller assumes landing elevation of 2,000’ if FMS or MAN landing altitude is unavailable
Ground:
Takeoff - small positive pressurization is provided just prior to rotation
Landing - outflow valves open to depressurize aircraft
How many pressure relief valves?
- 2 positive pressure relief valves (9.4 PSI)
- negative pressure relief valves on each cargo door (number depends on aircraft) - relieve existing differential pressure when doors are open
Bleed Air Sources
- APU
- ground source
- engine (IP or HP)
What is bleed air used for?
- air conditioning
- pressurization
- engine starting
- wing and nacelle anti-ice
- leading edge flaps
- aft cargo heat
- cargo smoke detection
- air driven hydraulic demand pumps
- potable water pressurization
- hydraulic reservoir pressurization
- thrust reversers
Sources of Engine Bleed Air
- Intermediate Pressure (IP) section - used during high power setting operations
- High Pressure (HP) section - used during descent and low power setting operations
When does engine bleed valve close?
- ground cart is supplying air
- bleed over temperature
- bleed over pressure
- loss of bleed source
- bleed duct leak
- engine fire switch pulled
What opens the start valve during engine start?
For Autostart:
- Engine Start switch arms the start valve
- EEC opens start fable when Fuel Control switch to RUN
For Manual start:
- Engine Start switch opens the start valve
How many sections of the Bleed System?
- 3 sections (Left, Center, and Right) separated by 2 isolation valves (Left and Right)
When is APU RUNNING displayed on EICAS
APU N1 95% or greater
Primary use for APU Bleed
- engine starting
- pack operation on the ground (air conditioning)
Where are check valves located in the Bleed system?
- APU supply duct
- Ground Supply duct
- IP section
What causes Pressure Regulating Valve (PRV) to close?
- bleed air overheat
- start valve failed to closed
- engine bleed HP valve failed open
Under what conditions would High Pressure (HP) air be used?
- Descent
- Other low power setting operations
Under what conditions would Intermediate Pressure (IP) air be used?
High Power Settings
The Engine Bleed Air Switches control which valves by system logic, when bleed air pressure is available?
- Engine bleed air valve
- Pressure Regulating Valve (PRV)
- HP bleed valve
Describe the general function of the Pressure Regulating Valve
The PRV limits bleed air pressure to prevent damage to ducting and equipment downstream.
With the HP valve failed open and the respective bleed air switch OFF will nacelle anti-ice be available?
No
An Engine Bleed Air System (SYS) FAULT light indicates what?
- Bleed air overheat
- Bleed air overpressure
- HP bleed valve open when commanded closed
- PRV open when commanded closed
What does a bleed duct Isolation (ISLN) VALVE light indicate (amber)?
Isolation valve position disagrees with switch position
What happens if the engine start valve fails to close?
- Bleed air is isolated from the engine starter (protects the starter)
- The PRV remains closed
- The engine bleed air valve remains closed
- Nacelle anti-ice and thrust reverse are not available for the respective engine
What 2 valves close in the engine if a bleed are overheat is detected?
- PRV
- HP valve
What conditions in the engine bleed air system would prevent nacelle anti-ice operation when the bleed air switch is ON?
- The PRV has failed closed, or
- The PRV has been closed due to a bleed air overheat (Fan Pre-cooler not working), or
- The start valve is not closed
How would you isolate a bleed air duct section in the event of a bleed duct leak is detected?
- Close the respective isolation valve
- Close the engine bleed air valves
Do we normally operate with the Isolation Valves open or closed?
Open
If the center duct is isolated how is temperature controlled in all temperature zones?
- All temperature zones operate in backup temperature control mode
- Trim air is unavailable
With a left or right duct isolated how would the leading edge flaps extend on the affected side and what EICAS Advisory message would display?
- The respective LEF would operate in secondary mode (electric)
- FLAPS PRIMARY (until LEF extended)
How does an isolated left or right duct affect the hydraulic systems?
The respective hydraulic demand pump 1 or 4 is turned off
What two systems use engine bleed air downstream in the engine prior to the engine bleed valve?
- Nacelle anti-ice
- Thrust reverse
How are the engine bleed air valves actuated and when do they open for forward flow?
- The bleed air valves are pressure activated
- They remain closed until engine bleed air pressure causes forward flow
Which areas does each pack receive bleed air from?
- Pack 1 from left pneumatic manifold
- Pack 2 from center pneumatic manifold
- Pack 3 from right pneumatic manifold
- can receive bleed air from any engine with isolation valves open
How is the pneumatic manifold decided?
- 3 sections decided by two isolation valves
- left manifold section supplied by ENG 1 and ENG 2
- center manifold section supplied by APU or Ground Air
- right manifold section supplied by ENG 3 and ENG 4
Temperature range with temp selectors
Upper Deck: 18ºC (65ºF) - 29ºC (85ºF)
Main Deck: 4ºC (40ºF) - 29ºC (85ºF)
FWD/AFT Lower Lobe: 4ºC (40ºF) - 29ºC (85ºF)
When is High Flow selected?
- Manually via HI FLOW switch (PACKS HIGH FLOW memo)
- Automatically by:
- position of Lower Lobe Cargo Conditioned Air Flow Rate selector
- phase of flight (Hi on the ground, climb, and descent)
- number of operation packs
- Automatically when packs shut down or fail
- normal flow at FMC Cruise altitude or VNAV PATH
Ventilated areas
- Lavs
- Galley
- Flight Deck crew rest
- supernumerary seat gaspers
- two ventilations fans (primary and back up) for galley and lavs
What happens when you turn the Pack Control Selector Off
- closes associated Pack Valve
- resets Pack Fault Protection
- extinguishes SYS FAULT Light
- Pack 1, 2, or 3 OFF memo
How do you know which Pack Temp Controller is in operation?
Displayed on ECS synoptic display
How are pack valves controlled?
- Pack Control Selector to NORM, A, or B
- electrically signals valve to open
- bleed air pressure opens pack valve
Benefits of Normal Flow rate
- minimize bleed air demand
- reduce engine fuel consumption by 0.3%
Pack system SYS FAULT Light
- PTC/other system Fault
- pack overheat
What happens if both PTCs A and B fail?
- Packs will operate in backup mode
- pack overheat protection continues
Equipment Cooling selector NORM (On ground, Warm Ambient Temp)
Equipment Supply Valve - Open
Supply Fan ——> electrical equipment
Exhaust Air ——> Ground Exhaust Valve (Open)
Inboard Exhaust Valve - Closed
E and E exhaust routing depends on
- routing depends on:
- ambient temp
- lower lobe cargo conditioned air flow rate selector (LLCCAF)
- forward lower lobe cargo temp selector
Equipments Cooling selector NORM (On ground, Cold Ambient Temp)
Flight Config: Equipment Supply Valve - Open Supply Fan ——> electrical equipment Exhaust Air ——> Inboard Exhaust Valve (Open)——> FWD Cargo Ground Exhaust Valve - Closed
What E and E configuration is automatically selected with one engine running on each wing?
Flight Configuration
*allows for cabin pressurization
EQUIP COOLING selector STBY
Manually selects Flight Configuration
EQUIP COOLING: NORM
One or more engine running on each wing
LLCR selector: OFF, AFT LOW, AFT HIGH, or 10ºC or higher selected
- Flight Config Open Loop
Equipment Supply Valve - Open
Supply Fan ——> electrical equipment
Exhaust Air ——> Inboard Exhaust Valve (Open)——> FWD Cargo
Ground Exhaust Valve - Closed
EQUIP COOLING: NORM
One or more engine running on each wing
LLCR selector: FWD LOW, BOTH LOW, FWD HIGH, or 10ºC or less selected
Flight (Closed Loop)
Flight Deck Equipment Cooling Source Valve - Closed Loop (no conditioned air)
Equipment Supply Valve -Closed (No Cabin Air)
Supply Fan ——> electrical equipment
Exhaust Air ——> Bypass Valve (Open)
Ground Exhaust Valve - Closed
Inboard Exhaust Valve - Closed
EQUIP COOLING EICAS message
E and E Cooling System not properly configured
Single fault detected in E and E system?
- system configure to closed loop mode
- no EICAS message to alert crew
- status page message for maintenance
EQUIP COOLING OVRD
- Flight Deck Equipment Cooling Source Valve - Closed
- selected with both internal fans inoperative
- cooling via reverse airflow from flight panels
- Equip Supply valve - closed
- ground exhaust valve - closed
- Inboard exhaust valve - closed
- Bypass valve - closed
- Smoke/Override valve - open
- differential pressure exhaust air overboard
What is the source of bleed air for thrust reversers?
- HP Bleed from respective engine
* HP is needed for thrust reverse operation
How do the cabin altitude controllers calculate cabin pressurization schedule?
- ambient pressure
- flight plan data from FMC
When does the cabin altitude controller enter descent mode and what happens?
- T/D
- initial descent approx 1,000’ from cruise
- controller decreases or increases cabin altitude to slightly below the FMC planned landing altitude in AUTO or the landing altitude set in MAN
- The slight altitude difference assures a small positive pressurization at touchdown
When is the protection of the cabin altitude limiter?
Closes both outflow valves if cabin altitude exceeds 11,000’
What altitude is assumed by the cabin altitude controllers if landing altitude is not available from the FMC, and MAN is not selected?
2,000’
What action would allow you to gain manual operation of the pressurization system?
- Turn both Outflow Manual switches to ON
- Bypasses all automatic cabin altitude control functions
Describe the cabin altitude controller CLIMB mode
- cabin altitude increases on a schedule based on airplane climb rate and flight plan cruise altitude
- FMC climb path planned level segment are included
- Cabin altitude continues to increase during the level segment
Is automatic PTC switch available with TRIM AIR off?
- PTC A is automatically selected
- auto and manual selection of PTC B is inhibited, unless PTC A fails (inhibition will be removed)
How is pack outlet temperature determined
The zone required the coolest temp control pack outlet temp
Lower Lobe Cargo Conditioned Air Flow Rate - OFF
All lower lobe conditioned air is off
- FWD and AFT Trim Air Valves closed
- FWD and AFT Conditioned Air valves closed
FAN AIR switch
- turns on and off flight deck fan
- recirculated air in the cockpit
Trim Air Off
- Master Trim Air valve closes
- Pack output temp to backup
- PTC A selected (auto/mam selection of PTC B inhibited unless failure of A)
- temp control of upper deck and crew rest areas inhibited
ZONE RST SYS FAULT Light
- ZTC fault or overheat in temp zone duct
- Master trim air valve failed closed
- TRIM AIR Switch OFF
- master trim air valve closed and pack air continues to flow
When is Trim Air unavailable to Flight Deck, Upper Deck, Crew Rest, and Main Deck areas (temp control reverts to back up mode)
- TEMP ZONE EICAS Advisory
- TRIM AIR OFF EICAS Advisory
- Master Trim Air switch Off
- center bleed duct isolated
How is temperature modulated in backup mode
- depends on which settings are avail to PTCs
Zone duct overheat:
* FLT DECK TEMP selector is operative - regulates all pack to an averages of 18ºC - 29ºC
Zone Controller fault:
- FLT DECK TEMP selector failed; then
- PACK outlet temp regulates to last flight deck temp set; or
- average of 24ºC
What happens when either pressure relief valve is open?
Pack 2 will automatically shutdown to assist in relieving cabin pressure
What is supplied by the Right Bleed Manifold?
- LE Flaps
- HYD 3 and 4 Reservoir Press
- Wing Anti-Ice
- # 4 Hydraulic Demand pump
- Pack 3
What is supplied by the Center Bleed Manifold?
- Trim Air
- Aft Cargo Heat
- Pack 2
- Cargo Smoke Detectoin
- Lower Lobe Cargo Air Con Trim Air
What is supplied by the left bleed manifold?
- LE Flaps
- HYD 1 and 2 Reservoir Press
- Wing Anti-Ice
- # 1 Hydraulic Demand pump
- Pack 1
When is Bleed Air unavailable for thrust reverser operation with the Engine Bleed Air switch ON?
- PRV failed closed
- PRV closed due to bleed air overheat
- start valve is not closed
Purpose of the fan air precooler
Regulates Bleed air temperature
What does the PRV protect with the start valve open?
Protects the engine compressor sections from reveres air flow during engine start
LLCCAFR switch FWD LOW or AFT LOW
FWD LOW:
- Pack 3 hi flow
- Pack 1 and 2 normal flow
- 2/3 of PACK 3 airflow to FWD lower lobe
AFT LOW:
- Pack 2 hi flow
- Pack 1 and 3 normal flow
- 2/3 of PACK 2 airflow to AFT lower lobe
LLCCARF BOTH LOW, FWD HIGH, or AFT HIGH
- All PACKS HI
Both LOW: 2/3 of PACK 2 ad 2/3 of PACK 3 to respective lower lobes
FWD HI: All of PACK 3 flow to FWD lower lobe
AFT Hi: All of PACK 2 flow to AFT lower lobe
Where is the temperature controlled for the Upper Deck and Crew Rest Area
Cabin Temperature Panel on the Lav Wall
When do the positive pressure relief valve open? Can they be be closed?
- open if cabin pressure becomes excessive
- pack 2 shuts down to assist in relieving excess cabin pressure
- part of the valve will close when cabin press is no longer excessive
When do the negative pressure relief valves open?
- located on side, fwd, and aft cargo doors
- open when airplane cabin pressure is slightly less than outside air pressure
- open to relieve any existing pressure when cargo door is unlatched
Does the deck fan operate in flight?
- operates on the ground only to recirculate air in the flight deck
Functions of the Zone Temperature Controller
Controls commanded temperature by:
- setting the cold pack outlet temperature
- modulating trim air to selected zones by positioning zone trim air valves
How is temp controlled when AFT or LWR Lobe in back up mode?
- if FWD/AFT LWR Lobe Cargo Temp selector available to PTC, pack three/two outlet temp regulated to achieve the temp set by the selector, or
- if FWD/AFT LWR Lobe Cargo Temp selector unavailable to PTC, pack three/two outlet temp regulated to achieve the cargo temp sensed at time backup mode initiated, or
- if FWD/AFT LWR Lobe cargo temp unavailable to PTC, pack three/two outlet temp controlled to the pack outlet temp sensed at time backup mode initiated
How can you attempt to restore zone temp control and clear back up mode?
FLT DECK, UPPER DECK, CREW REST, FWD MAIN, AFT MAIN: push ZONE RST switch
LWR FWD/AFT Cargo Lobe: associated Temp controller from AUTO to MAN or MAN to AUTO; also LLCCAFR selector to OFF
AFT Cargo TEMP light
- AFT cargo compartment temp excessive
- overheat shutoff valve closes
