How do you set up the pressurization controller for automatic mode?
Set the destination/landing field elevation+ 200 ft.
Will the aircraft remain pressurized if one of the air conditioning packs is turned off?
Yes
Which outflow valve is used during automatic mode?
Aft Outflow valve
When would you use manual pressurization?
If the Automatic mode becomes inoperative. Either the Automatic mode fails or the FAULT light comes on.
How is manual pressurization operated?
Manual Differential Control Switch (three position, spring loaded to center position):
A. With mode select switch set to MAN position, pushing the switch left to INCR, increases the cabin pressure differential and decreases cabin altitude, by closing the Aft Outflow valve.
B. Pushing the switch right to DECR, decreases the cabin pressure differential and increases cabin altitude, by opening the Aft Outflow valve.
When is take-off memorization cancelled?
- more than 10 min after takeoff
What is take-off memorization mode?
The compute pressurization Control (CPC) is in take-off mode for approx 10 min after lift off. This avoids the requirement to reselect the landing altitude in case of an aborted flight and return to the departure airport.
10 min after take-off the memorization remains in effect as long as:
- the scheduled cabin alt is higher than the theoretical cabin altitude, or
- the aircraft alt is less than the takeoff alt plus 5,000 ft. (Valid only for takeoff alt over 8,000 ft.)
What does the forward outflow valve selector do?
Can be used to manually open the Forward safety Outflow valve.
Normal operations, lever is kept in NORMAL position with guard down (closed). When selected OPEN (emergency operations), the valve is fully opened.
It cannot be regulated, it is fully open or fully closed.
When does the CABIN PRES warning light illuminate?
If cabin altitude exceeds 9,800ft
What is the Aft safety Outflow valve used for?
It supplies additional venting during ground operation.
The valve opens on the ground when at least one engine is running at idle, or when the APU is operating to supply additional bleed air venting.
How is the aft outflow valve opened and closed?
By the pressure select switch which has three positions (modes):
- AUTO, with AUTO selected, cabin altitude is automatically controlled by the cabin pressurization via the Aft Outflow valve which modulates to maintain a pre-programmed cabin altitude schedule.
- MAN, selecting MAN turns off the cabin pressure controller and enables manual control of the cabin differential pressure via the Aft Outflow valve by using the MAN DIFF (manual Differential) switch located directly below the mode select switch. Pushing the switch to INCR, increases cabin press by closing the Aft Outflow valve. DECR, decreases the cabin press diff by opening the Aft Outflow valve.
- DUMP, selecting DUMP fully opens the Aft Outflow valve to dump cabin pressure. Can be used whenever smoke is present in the cabin to maximize smoke evacuation from the cabin through the Aft Outflow valve.
It is an electronically controlled valve located on the aft pressure dome. It is regulated by the cabin pressure controller (computer) in response to pressurization control panel inputs.
How is the forward outflow valve opened and closed?
- FWD Safety Outflow valve Manual Control Knob (rotary action) on the pressurization Control panel overhead, opens and closes the Forward Safety Outflow valve. (Cabin pressure can be regulated by turning this Knob as necessary in case of Aft Outflow valve failure)
- The Forward Safety Outflow valve selector (Right of f/o’s knee), can also be used to manually open the Forward Safety Outflow valve.(can’t be regulated, full open or closed)
What does the environmental control system provide?
Modulates the amount of bleed air from the both engines.
What is the maximum differential pressure permitted by the CPC (computer pressure control)?
5.46 psi, which gives a cabin altitude of 8,000 ft at 25,000 ft ambient altitude.
