Pneumatics and Pressurization Flashcards
What systems require bleed air?
Air Conditioning
Wing Anti-Icing
Engine Starting
Hyd reservoir pressurization
Water pressurization
Where is the pressure supplied from?
Engine bleed
APU bleed or
External High Pressure ground connection
Bleed air is usually supplied from the Intermediate Pressure stage except for…
Idle conditions where the High Pressure stage supplies the bleed air.
Note: IP and HP bleed is never used at the same time
How is the bleed air cooled?
With a pre-cooler using cool air from the fan section
What is the max altitude for APU bleed?
20,000 feet
What side is the APU bleed connected to?
1 engine side, the crossfeed valve supplies APU bleed to both sides
What is unique about APU bleed air priority?
The APU has priority supplying bleed air
What is a limitation with the External High Pressure air connection?
When connected, DO NOT use any other bleed source!
Where are the leak detection loops?
APU ducting
Engine Pylon ducting
Wing ducting
What does BMC1 control?
Bleed air from Engine 1 and APU
What is special about the wing ducting?
There are 2 leak detection loops in the wings. Each monitored by different BMCs. Both loops must detect a leak for a pilot alert. Otherwise, the leak is automatically isolated.
Why would the Engine Number on the BLEED page be amber?
When the engine is below idele (off)
What happens to the associated PACK when you manually close an engine bleed valve?
Turning off the engine bleed valve automatically shuts off the associated Air Conditioning PACK.
How is the engine bleed valve closed by the pilot?
END BLEED pb OFF
OR
ENG FIRE pb engaged
Why would the BMC close the engine bleed valve?
Over temp
Over Pressure
Bleed Leak
Engine Start sequence
APU Bleed selected ON
How would Physics close the engine bleed valve?
No air pressure (spring loaded closed)
If reverse pressure is sensed
When will the auto X BLEED valve open?
When APU bleed is selected on.
What happens to the PACK control valve during engine start?
They automatically close to provide max pressure for engine start.
They will auto open ~30 seconds after start sequence
If a engine bleed fails during icing conditions, what is a limitation?
One engine bleed CAN NOT operate both PACKs when de-icing is on
During an engine bleed failure, can you use APU to supplement pressure?
NO, remember if you select APU bleed this will automatically close both engine bleed valves!
What is a icing limitation during a bleed air leak?
You CANNOT XFEED bleed air because of the leak as this will feed it the leak. Since you do not want to de-ice only one wing, you must depart icing conditions.
+8.6psi and -1.0psi
What are the max pressure differentials for the two safety v
Two Pressurization Controllers and a backup manual controller
How is pressurization controlled?
Automatically depressurizes in case of abnormal residual pressure on the ground.Activates if (all conditions):The outflow valve does not fully openBoth CPCs fail or manual modeAC on the groundEngines are shutdown or <100knots
What does the Residual Pressure Control Unit do? (A320 only)
FMS, LGCIUs, ADIRs and throttle position
What are the inputs to the Pressure Controllers?
Destination airport is not in the FMS databaseORBoth FMGCs fail
When would you have to set the landing elevation?
Outflow valve (if not set to MAN)Emergency Ram Air InletAvionics ventilation inlet and extract valvesPack flow control valvesForward cargo isolation valves
What does the DITCHING pb close?
When TOGO power is set, the controller starts cabin pressure climb at 400fpm until delta P is 0.1psi. Aborted takeoffs revert to ground mode.
What happens during takeoff?
Below 8000’less than normal climb ordescent >200fpm for 30 secondsPressure reset to +0.1psi until climb re-initiated
When will the pressurization system enter Abort mode?
8psi
What is the max delta presurization?
-750fpm, after touchdown it continues at -500fpm
What is normal rate of cabin decent?
After each landing
When does the pressurization controller switch to the other
500fpm
When in MAN mode, what is the target cabin VSI?
Displayed in white when the aircraft is on the ground.
On the SD, when is GND displayed?
- 2 - If one BMC fails, the adjacent BMC takes over the monitoring of the bleed system to issue the following ECAM warnings:o Over pressureo Over temperatureo Wing leak.- BMC 1 lost: (ENG 1) APU leak detection lost.- BMC 2 lost: (ENG 2) GEN 2 leak detection lost.
How many BMC’s are there? What happens if left or right BMC fails?
When idle.- Air is normally bled form the intermediate pressure stage (IP) of engine’s high-pressure (HP) compressor to minimize fuel penalty.- At low engine speed, when the pressure and temperature of the IP air are to low, the system bleeds air from the HP stage and maintain it at 36+/-4PSI.- An intermediate pressure check valve downstream of the IP part closes to prevent air from the HP stage from being circulated to the IP stage.
During normal operation when would you expect to see the HP valve OPEN?
- A pre-cooler downstream of the bleed valve regulates the temperature of the bleed air.- The pre-cooler is an air-to-air heat exchanger than uses cooling air bleed from the engine fan to regulate the temperature to approximately 200 degrees.
How is the Bleed Air Temperature regulated and to what temperature?
- The bleed valve, which is downstream of the junction of HP and IP ducting, acts as a shut-off and pressure regulating valve.- It maintains delivery pressure at 45+/-5PSI.- May fluctuate between 38 ~ 56PSI with max peak-to-peak pressure of 16PSI) at high engine power to FL100).
How is the bleed air pressure regulated? What is the normal pressure?
- 2 electric motors, one for automatic, one from manual mode, control the valve.- In automatic mode, the crossbleed value opens when the system uses APU bleed air. It closes, if the system detects an air leak, except during engine start.
With the cross-bleed selector in AUTO, what controls the position of the crossbleed valve?
It closes. Except during engine start.
What happens if a bleed leak occurs with the crossbleed selector in AUTO?
APU
Which bleed (engine or APU) has priority?
The FAULT light goes out when the ENG BLEED p/b switch is OFF if the fault has disappeared.
Does the overhead panel FAULT light extinguish when the temperature drops following a bleed overheat?
The FAULT light goes out when the ENG BLEED p/b switch is OFF if the fault has disappeared.
When do the bleed air temperature drops following bleed overheat?
- Pre-cooler outlet temperature overheat 290 degrees for > 5sec, 270 degrees for > 15sec, 257 degrees for > 55sec, or < 4PSI, or if overpressure detected by BMC (threshold 57-60PSI).
When do the bleed air temperature and pressure go amber on the S.D?
Yes, if only one pack operating.
Is WAI allowed if only one bleed system is operating?
LP: Packs 1+2 OFF, to prevent pack contamination.HP: Do NOT use packs + APU bleed.
What should you NOT do if GD LP Air is connected? And the HP air?
2
How many Automatic Cabin Pressure Controllers are there?
- 3 (2 auto AC, a manual DC)- Slow on DC for manual to slow OFV.
How many motors can drive the Outflow Valve?
> 8.6 PSI or < 1 PSI
What causes a safety valve to operate?
Before takeoff and 55secs after landing, the outflow valve fully opens to ensure that there is no residual cabin pressure. At touch down, any remaining cabin pressure is released at a cabin v/s of 500’/min.
What is the OFV position with the AC on the ground?
The cabin attitude varies according to a fixed pre-programmed law that takes into account the aircraft’s actual ROC.
During climb, cabin ROC is a function of what?
750’/min
What is the (approx.) Max ROD of the cabin in AUTO?
- At touch down, any remaining cabin pressure is released at a cabin v/s of 500’/min.- 55sec after landing, valve fully opens.
What happens to the OFV after touchdown?
- Pressure Difference: decreases- Cabin Vertical Speed: increases- Cabin Altitude: increases- OFV: selecting UP moves the valve towards the open position.
If the MAN V/S CTL is moved UP, what happens to the Press Diff, Cabin V/S, Cabin Alt, and OFV?
Close the OFV (only if its in auto position, not in manual position), emergency ram air valve. Inlet, avionics ventilation inlet and extract valves, pack flow control valves.
What does the Ditching switch do?
Phase 5-7 (lift off til touchdown)
When is cabin v/s displayed on the doors SD?
Overpressure overtemperature and wing leak.
Which failure in the bleed system causes an ECAM warning?
The bleed valve which is downstream of the junction of HP (high pressure) and IP (intermediate pressure) ducting acts as a shut-off and pressure regulating valve. It maintains delivery pressure at 45 +/- 5 psi.
How does the bleed pressure regulation work?
A precooler downstream of the bleed valve regulates the temperature of the bleed air. The precooler is an air-to air heat exchanger that uses cooling air bleed from the engine fan to regulate the temperature to approximately 200°C.
How does the bleed temperature regulation work?
Air conditioning engine starting wing anti-ice water pressurization and hydraulic reservoir pressurization.
Which systems or components are supplied by high pressure air?
Two Bleed Monitoring Computers (BMC).
Pneumatic system operation is controlled and monitored by…
Engine bleed systems APU load compressor and HP ground connection.
What are the high pressure air sources?
The crossbleed valve on the crossbleed duct allows the air supply systems of two engines to be isolated or interconnected.
What is the function of the crossbleed valve?
If one BMC fails the other one takes over most of the monitoring functions.
What occurs if one Bleed Monitoring Computer (BMC) fails?
BLEED page.
On which ECAM page you will get information about the PNEUMATIC system?
The APU bleed valve operates as a shut-off valve to control APU bleed air. It is electrically controlled and pneumatically operated.
How does the APU bleed valve work?
Leak detection loops detect any overheating near the hot air ducts in the fuselage pylons and wings. For the pylon and APU the sensing elements are tied to form a single loop and for the wing a double loop.
How does the bleed leak detection work?
Bleed leak (APU Bleed valve closes)
What does the amber “FAULT” light in the APU BLEED pushbutton indicate?
- When APU valve is open, the x-bleed valve is open- When APU bleed valve is closed, the x-bleed valve is closed- X-bleed also closes for wing, pylon, or APU duct leak (Except during engine start)
What logic control the X-Bleed valve when the X-BLEED switch is in auto?
No. When the APU MASTER sw is selected OFF, the bleed air valve is closed and the APU is allowed to cool prior to shutdown
If the APU is running, is it necessary to manually select APU BLEED OFF prior to APU shutdown?
2 Bleed Monitored Computers (BMC)
The pneumatic system is monitored and controlled by?
Yes, they are interconnected. If one BMC fails:- APU and ENG 1 leak detections are not monitored- ECAM APU BLEED LEAK warning is lost
If one BMC fails, can the other take over?
The GND unit temperature and pressure are indicated on the ECAM BLEED PRECOOLER 1
On the ECAM Bleed page, how do you tell if the GND HP air supply is connected?
Turn off the CAB FANS pushbutton, open the air vent on the instrument panel and confirm no airflow.
How can you tell if the GND LP air supply is removed before selecting the APU BLEED pushbutton to on?
HI
What flow rate is automatically selected when APU bleed air is in use or during single pack operation?
Engine speed is automatically increased to provide adequate bleed air pressure
If the engine bleed air in-flight is too low, what will occur?
APU Bleed
After engine start with the APU BLEED pushbutton ON, what source is supplying bleed air to the packs?
An APU bleed leak
What does an amber “FAULT” light in the APU BLEED pushbutton indicate?
It becomes amber when out of normal range delta P 8.5 psi.
When does the delta P indication become amber?
The DITCHING pb closes the outflow valve the emergency ram air inlet the avionics ventilation inlet and extract valves and the pack flow control valves.
What is the function of the DITCHING pushbutton?
There are two automatic motors and one manual motor.
How many motors are available to operate the outflow valve?
Ground (GN)Takeoff (TO)Climb (CL)Cruise (CR)Decent (DE)Abort (AB).
Pressurization is assumed through the following modes…
Two identical independent digital controllers automatically control the system by maintaining the proper cabin pressure. They receive signals from the Air Data Inertial Reference System (ADIRS) the Flight Management and Guidance Computer (FMGC) the Engine Interface Unit (EIU) and the Landing Gear Control Unit (LGCIU).
How does the cabin pressure control work?
Two cabin pressure controllers (CPC) one residual pressure controller (RPCU) one outflow valve one control panel and two safety valves.
What are the main components of the pressurization system?
Two independent pneumatic safety valves prevent cabin pressure from going too high (+8.6psi above ambient) or too low (-1psi below ambient).
How many safety valves are installed?
Switching the MODE SEL pb to MAN for at least 10 seconds then returning it to AUTO will select the other system.
Can you switch between the two cabin pressure controller (CPC)?
The outflow valve is on the right hand side of the fuselage behind the aft cargo compartment and below the flowtation line.
Where is the outflow valve?
It becomes amber when the V/S is greater than 2000ft/min or less than -2000ft/min
When does the cabin vertical speed (V/S) indication of the cabin pressure become amber?
The RPCU automatically depressurizes the aircraft in case of abnormal residual pressure on the ground.
What is the purpose of the Residual Pressure Control Unit (RPCU)?
If the aircraft does not climb after takeoff the abort mode prevents the cabin altitude from climbing. Cabin pressure is set back to the takeoff altitude + 0.1psi.
What is the function of the abort mode?
The indication becomes red for excessive cabin altitude >= 9550ft.
When does the color of the cabin altitude indication on the ECAM change to red?
The safety valve opens when the cabin differential pressure is between 8.2 and 8.9 psi. The range is due to the reduced accuracy of delta P measurements (in MAN mode) combined with the decrease in cabin differential pressure that occurs immediately after the safety valves open.
When does the safety valve open?
Ground functionPre-pressurizationPressurization during flightDe-pressurization
What are the four general functions of the cabin pressurization system?
AUTO:FMGS data used to construct an optimized pressure schedule.Other position:The pressurization schedule does not use the landing elevation from the FMGS, but instead uses the landing elevation selected with this knob (from – 2,000 to + 14,000 feet) as its reference.
LDG ELEV selector
(CABIN PRESS Panel)
- AUTO
- Other position
AUTO:Automatic mode is operating. One of the two cabin pressure controller moves the outflow valve. Recycling this pb (MAN 10 sec then back to AUTO) switches controllers.MAN:MAN V/S CTL switch to control the outflow valve.FAULT Light:With ECAM caution light comes on only when both automatic systems are faulty.
MODE SEL pb
(CABIN PRESS Panel)
- AUTO
- MAN
- FAULT Light
Springloaded to neutral. Controls the outflow valve position through operation of the MAN motor, when the MODE SEL pushbutton is in the MAN position.UP: The valve moves towards the open position.DN: The valve moves towards the closed position
MAN V/S CTL toggle sw
(CABIN PRESS Panel)
- UP
- DN
ON:sends a “close” signal to:- fwd cargo isolation outlet valve The cargo recirculation fans stop automatically.- avionics ventilation inlet and extract valves- emergency ram air inlet- pack flow control valves- outflow valve
DITCHING guarded pb
(CABIN PRESS Panel)
- ON
AUTO (Both pb):Open/closed config depending on temperature until TO power, then closed or intermediate.(Either pb in OVRD):- Closed config. A/C system supplies cooling.- With BLOWER pb in OVRD blower fan stops.(Both pb in OVRD):- Air flows from the a/c sys and then overboard- The extract fan continues to run.FAULT Light (blower pb):- blowing pressure low- duct overheats- computer power supply fails- smoke warning is activatedFAULT Light (blower pb):- extract pressure is low- computer power supply fails- smoke warning is activated.
BLOWER and EXTRACT pb
(VENTILATION Panel)
- AUTO
- OVRD
- FAULT Light
Auto:- The inlet and outlet isolation valves open.- The extraction fan runs when the aircraft is on ground, or if diff P 1 psi, the fan stops.- If smoke is detected in the forward cargo bay, the valves close and the fan stops.OFF : The inlet and outlet isolation valves and the trim air valve close; the extraction fan stops.FAULT lt:With the ECAM caution when either inlet or outlet valve is not in the selected position.
FWD ISOL VALVE pb
(CARGO HEAT Panel)
- Auto
- OFF
- FAULT Light
- COLD: Approximately 5° C (41° F)- Middle position: Approximately 15° C (59° F)- HOT: Approximately 26° C (79° F)
Temperature selector (CARGO HEAT Panel)
- COLD
- Middle position
- HOT
- COLD position: 18°C (64°F)- Middle position: 24°C (76°F)- HOT position: 30°C (86°F)
Zone temperature selector sw:
(AIR COND Panel)
- COLD
- Middle
- HOT
ON:Hot Air Pressure Regulator Valve regulates hot air pressure.OFF:Valve closes, and the trim air valves close. The FAULT circuit is reset.FAULT light on:duct overheat temp = 88°C (190°F).Triggers ECAM msg.The valve and the trim air valves close automatically.The FAULT light goes off when temp < 70°C (158°F), and the flight crew selects OFF.
HOT AIR pb
(AIR COND Panel)
- ON
- OFF
- FAULT light
ON:Pack flow control valve is automatically controlled.It opens, except:- Upstream pressure below minimum;- Compressor outlet overheat;- Engine start sequence;- Fire pb on same side is pressed;- Ditching pb ON;OFF:The pack flow control valve closes.FAULT LT:Comes with ECAM- valve position disagree with selected position- compressor outlet overheat- pack outlet overheat
PACK pb
(AIR COND Panel)
- ON
- OFF
- FAULT Light
ON:ECON flow is selected.OFF:Normal flow is selected. Normal flow provides 20 % more than ECON flow.
ECON FLOW pb (321)
(AIR COND Panel)
- ON
- OFF
LO (80 %)NORM (100 %)HI (120 %)Goes into high when automatically when:- single pack operation- with APU bleed supplyIf LO is selected, the pack flow can be automatically selected up to 100 % when the cooling demand cannot be satisfied.
PACK FLOW sel (319)
(AIR COND Panel)
- LO
- NORM
- HI
ON:- The RAM air inlet opens if the DITCHING pb is not selected ON.- If differential press => 1 psi: The outflow valve control remains normal. No emergency RAM air flows in.- If diff press < 1 psi: The outflow valve opens to about 50 % when under automatic control. It does not automatically open when it is under manual control. Emergency RAM airflow is directly supplied to the mixer unit.OFF:The RAM air inlet closes.
RAM AIR pb (guarded)
(AIR COND Panel)
- ON
- OFF
ON:The two cabin fans are on.OFF:The two cabin fans are off.
CAB FAN pb
(VENTILATION Panel)
- ON
- OFF
On:The valve is open, and supplies low pressure oxygen to the masks (normal position in flight).OFF:The valve is closed, and the white light comes on.
CREW SUPPLY pb
(OXYGEN Panel)
- On
- OFF
This light comes on white, when the control for the oxygen mask doors is activated, and it remains on until the TMR RESET pb is pressed.
PASSENGER SYS ON Iight
OXYGEN Panel
AUTO:The mask doors open automatically when the cabin altitude exceeds 14,000 feet.Pressed:The mask doors open.
MASK MAN ON pb
(OXYGEN Panel)
- AUTO
- Pressed
FMGC database
From what source does the pressurization system obtain landing elevation?
2, only one is used at a time and they swap roles after each landing
How many controllers are in the pressurization system?
The pressurization system uses the manually selected landing elevation
When out of the AUTO position, what is different?
The pressurization system uses the manually selected landing elevation
When out of the AUTO position, what is different?
The pressurization system uses the manually selected landing elevation
When out of the AUTO position, what is different?
750 FPM
What is the maximum cabin rate of descent with the pressurization in AUTO?
1 psi differential or less
At what cabin differential pressure does the RAM AIR valve open?
- Avionics Inlet and Extract valves- Ram air Inlet- Pack Flow Control valves- Outflow valve (only if in Auto mode)
Which valves will receive a close command when the DITCHING pushbutton is depressed? (ARPO)
Not if the outflow valve is under manual control
Will the DITCHING pushbutton always close the outflow valve?
Yes, select MAN on the MODE SEL and use the MAN V/S CTL switch
Can the pilot control the outflow valve
Not if the outflow valve is under manual control
Will the DITCHING pushbutton always close the outflow valve?
2 pressure relief valves
What protects the air frame from excessive cabin differential pressure?
3 - One for each automatic controller and one for manual control
How many outflow valve motors are installed?
No
If PACK FLOW is selected to HI, will it automatically shift lower?
Switch MODE SEL to MAN for 10 seconds, then back to AUTO
How do you manually switch controllers?
Both automatic pressure controllers are faulty
What does an amber “FAULT” light in the MODE SEL pushbutton indicate?
- 8,800’: CAB ALT flashes- 9,550’: EXCESS CABIN ALT warning- 11,300’: All cabin signs illuminate- 14,000’: All passenger masks deploy
Describe what occurs when cabin pressure altitude exceeds:
- 8,800’
- 9,550’
- 11,300’
- 14,000’
Cabin temperature defaults to a set value
If the Lav/Galley Extract Fan fails, what occurs?
50 FPM
Approximately what rate of cabin change does 1 click of the MAN V/S CTL switch produce?
