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valve.
Positive and negative pressure relief valves protect the fuselage against excessive
pressure differential.
The pressurization system has automatic and manual operating modes. Other than
accomplishing normal procedures for entering FMC data, no specific flight crew
action is required for fully automatic operation.
Pressurization System Automatic Operation
In flight, the Cabin Pressure Control System (CPCS) operates in a climb mode, a
cruise mode, or a descent mode.
The CPCS uses ambient pressure and flight plan data from the FMC to calculate
a cabin pressurization schedule. The schedule provides a comfortable cabin climb
to cruise altitude.
For takeoff, the system supplies a small positive pressurization prior to rotation to
cause a smooth cabin altitude transition to the cabin altitude climb schedule.
In climb mode, cabin altitude increases on a schedule related to the airplane climb
rate and flight plan cruise altitude. When the FMC climb path has a planned level
segment, it is included in the total time required for the airplane to reach the top
of climb. Cabin altitude continues to increase during the planned level segment.
For unplanned level segments or when VNAV disengaged, cabin altitude will
remain constant as long as aircraft altitude is not changing. When the airplane
climb flight path is above the FMC climb path and maximum cabin pressure
differential is reached during the climb, cabin rate then becomes a function of
airplane climb rate so maximum cabin differential pressure is not exceeded.
If cruise altitude is unavailable from the FMC in AUTO, the CPCS assumes a
cruise altitude of 43,000 feet.
In the cruise mode, maximum cabin altitude is no more than 6,000 feet. The CPCS
enters descent mode after airplane descent has been initiated.
787 Flight Crew Operations Manual
Air Systems -
Pressurization System
Description
2.30.2 Boeing Proprietary
During descent, cabin altitude decreases to slightly below the FMC planned
landing altitude. This ensures that the airplane lands pressurized. Landing altitude
barometric pressure correction comes from the captain’s altimeter setting.
At touchdown, both outflow valves open to depressurize the cabin.
For high altitude takeoffs, if the takeoff field elevation is higher than 8,000 feet,
the cabin descends to the target altitude while the airplane is climbing.
For high altitude landings, if the destination airport elevation is greater than 8,000
feet, the cabin altitude climbs to 6,000 feet after takeoff and remains there during
cruise. The cabin altitude will then start climbing to the destination airport
elevation when appropriate.
Pressurization System Manual Operation
The pressurization system is in the manual mode when the OUTFLOW VALVE
switches are set to MAN.
The system is manually operated by:
• setting the OUTFLOW VALVE switches to MAN
• holding the related OUTFLOW VALVE MANUAL switch to OPEN or
CLOSE.
Outflow valve position is displayed on the EICAS display. If the outflow valve
position is not available on EICAS, holding the respective OUTFLOW VALVE
MANUAL switch in the desired position for 30 seconds will move the valve from
full open or close to the selected position.
Landing altitude (normally provided by the FMC) can be manually set using the
LANDING ALTITUDE selector. Landing field selection limits are 2,000 feet
below sea level to 14,000 feet above sea level. Pulling the selector out to the detent
removes the FMC landing altitude and displays pressurization system indications
on the EICAS display. The knob is rotated clockwise to increase or
counterclockwise to decrease the landing altitude setting. Two rates of increase or
decrease, low and high, are available in each direction from the spring–loaded
center position.
Operation With Loss of Cabin Pressurization
With a sudden loss of cabin pressurization, the outflow valves will close
immediately in an attempt to control the cabin pressure. After descent, when the
airplane and cabin altitudes are approximately equal, the outflow valves open to
protect the airplane against negative pressure differentials.
It is important that the flight crew not attempt to manually close the outflow valves
during the descent.
787 Flight Crew Operations Manual
Air Systems Chapter 2
Bleed Air System Description Section 40
Boeing Proprietary 2.40.1
2.40 Air Systems-Bleed Air System Description
Introduction
Bleed air is supplied by the engines and is only used for engine anti–ice
operations.
Engine Bleed Air Supply
Engine bleed air is supplied from a dedicated bleed port. The engine bleed air
　
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