All I can find...
The cabin altitude warning switches, are on the ceiling in the forward EE compartment.
There are two digital cabin pressure controllers (CPCs). Each CPC has its own systems interface and valve motor system. This gives the AUTO mode of control a dual redundant architecture. Only one CPC controls the outflow valve at any time. The other CPC is a backup. The active controller changes for every flight or when there is an autofail event.
The manual control system has its own valve motor system. This gives the pressurisation control system a triple redundant architecture. A sensor on each CPC senses pressure in the cabin.
The outflow valve has three motors:
• Two AUTO motors with electronic actuators
• One MANUAL motor.
Altitude switches in each electronic actuator (at the valve itself) override CPC signals and close the outflow valve if the cabin altitude is 14,500 feet. (A bit late in the game?) This function does not affect the manual mode of operation of the outflow valve.
The cabin altitude and differential pressure indicator is connected to the alternate static system.
The rate of climb indicator detects pressure changes from a port on the back of the indicator.
These things cause the auto fail function:
• Power loss
• Cabin altitude rate of change is too high (>2,000 slfpm)• Cabin altitude is too high (>15,800 ft)
• Wiring failures
• Outflow valve component failures
• CPC failures
• Cabin differential pressure is too high (>8.75 psi). Obviously didn't in the above case.
Flush operations of the vacuum toilet system can cause the cabin rate of climb indicator to momentarily show a high rate of climb indication. This is normal.
Last edited by stator vane; 2nd May 2017 at 08:49.
Reason: correction