21-20 Pressurisation Flashcards
What systems make up the pressurisation system?
1 x Residual Pressure Control Unit (RPCU)
2 x Cabin Pressure Controllers (CPC)
1 x outflow valve controlled by three motors (2 automatic and and one manual)
1 x control panel
2 x safety valves
What are the four general functions of the cabin pressurisation system?
1) ground pressurisation
2) prepressurisarion
3) pressurisation in flight
4) Depressurisation
What modes does the cabin pressure system operate?
Automatic, semi-automatically or manually
What and from where is information sent to the Cabin Pressure Controller?
FMGC - sends cruise flight level, landing elevation and destination QNH.
ADIRS - sends static pressure and barometric correction information
LGCIU - activates flight and ground mode
Engine Interface Unit - supplies thrust lever angle to set the prepressurisation mode.
When do the two independent safety valves open?
When differential PSI is above 8.6 PSI or below - 1 PSI.
What does the residual pressure control unit do? And what are the conditions?
It automatically depressurises the aircraft in case of abnormal residual pressure on the ground. It opens the outflow valve when:
1) outflow valve is not fully open, and
2) CPCs are failed, or manual mode is selected, and
3) the aircraft is on the ground and
4) all engines are shutdown, or all ADIRS indicate an airspeed below 100kts.
What controls the cabin pressure in automatic mode?
There two identical independent Cabin Pressure Controllers, each controls its own electric motor that operates the outflow valve.
Only one controller can operate at once.
What altitude does the CPC limit the cabin pressure to in the cruise?
8,000 ft in the cruise
What data does the CPC use when FMGC data is not available? (When it enters semi-automatic mode)
It uses the captains BARO reference from the ADIRS and landing elevation is selected on the overhead panel.
When do the Cabin Pressure Controllers automatically transfer?
1) 70 seconds after landing.
2) if the operating system fails.
What happens in ground pressurisation mode?
Before take off and 55 seconds after landing the outflow valve fully opens to remove cabin residual pressure.
Cabin pressure is released at a vertical speed of 500 ft/min
What happens in take off/ pre-pressurisation mode?
To avoid the surge of pressure at rotation, the aircraft is pre-pressurised at a rate of 400ft/min till differential pressure is 0.1 PSI.
What happens in climb mode?
Cabin altitude varies depending pre-programmed law that takes into account the aircraft’s rate of climb.
What happens in cruise mode? What’s the cabin altitude target? And max differential pressure?
The controller maintains cabin altitude at the higher of the level off altitude or the landing elevation but the cabin altitude target is limited to 8000ft and a max cabin differential of 8.06 PSI.
What is descent mode? What is the maximum rate of descent?
The controller maintains a rate of descent so that cabin pressure is landing field pressure +0.1 PSI shortly before landing. Maximum cabin rate of descent is 750ft/min.
When does the cabin differential pressure on the cabin pressure page go amber?
If differential pressure is less than 0.4 PSI or greater then 8.5 PSI.
When does the cabin altitude turn red on the cabin pressure page?
If the cabin altitude exceeds 9,550 feet.
When does the outflow valve turn amber?
When the valve opens more than 95% during flight?
