Aircraft cabin multi-differential pressure control system

A method for limiting a difference between cabin pressure and atmospheric pressure in an aircraft using a pneumatic cabin pressure control system that includes an outflow valve comprising at least an atmospheric pressure input port, the method comprising the steps of:

• selectively isolating and de-isolating the outflow valve atmospheric pressure input port from pressure changes;
• opening the outflow valve if the difference between cabin pressure and atmospheric pressure exceeds a first threshold value and the outflow valve atmospheric pressure input is de-isolated;
• and
• opening the outflow valve if the difference between cabin pressure and atmospheric pressure exceeds a second threshold value and the outflow valve atmospheric pressure input is isolated.

An aircraft pneumatic cabin pressure control system adapted to prevent the difference between cabin pressure and atmospheric pressure from exceeding a threshold value, the system comprising:

• an outflow valve having an input port adapted to be coupled to a source of atmospheric pressure, the outflow valve configured to move to an open position if the difference between cabin pressure and atmospheric pressure exceeds a first threshold value;
• an isolation valve coupled to the outflow valve input port and selectively movable between an open position, in which the outflow valve input port is in fluid communication with the source of atmospheric pressure, and a closed position, in which the outflow valve input port is isolated from the source of atmospheric pressure to thereby prevent the outflow valve from opening if the difference between cabin pressure and atmospheric pressure exceeds the first threshold value;
• and
• a secondary controller coupled to the outflow valve and configured to move the outflow valve to the open position if the difference between cabin pressure and atmospheric pressure exceeds a second threshold value that is greater in magnitude than the first threshold value.