Patent ID: 8011904

Claim:
A method of supplying pressurized air to a cabin of an aircraft comprising: powering at least one compressor using power taken off of a gas turbine engine, wherein the at least one compressor is a cabin air compressor; supplying air to at least one inlet of the cabin air compressor from a source of air; using an air supply selector valve to select the source of air supplied to the inlet dependent on a desired cabin pressure, the supply selector valve being connected to and selectable between at least two air sources having different pressures and being selected from the group consisting of a gas turbine engine core compressor, a fan bypass air, ambient air, or a boundary layer flowing over an internal or external surface of any component of an airframe, a nacelle or the gas turbine engine; and supplying compressed air at the desired cabin pressure from at least one outlet of the cabin air compressor to the cabin to provide the desired cabin pressure, the desired cabin pressure being a pressure that maintains the comfort of passengers and cabin crew on the aircraft, wherein the at least one compressor comprises first and second compressors being mounted on a common shaft and driven by a gearbox, a first inlet for the first compressor, a second inlet for the second compressor, and using an inlet selector valve to allow gas to enter either, or both, of the first and second compressors from the at least two air sources.