Abstract: A pneumatic system 131 for use with gas turbine engines 10 and aircraft 100. The pneumatic system 131 comprises a first engine core compressor bleed offtake in the form of an engine handling bleed offtake 140, and a second engine core compressor bleed offtake in the form of first and second cabin bleed offtake 132, 134, the handling bleed being configured to supply higher pressure air than the cabin offtakes 132, 134. The system 131 comprises a turbocompressor 144 comprising an air compressor 148 driven by a turbine 146. The handling bleed offtake 140 is in fluid communication with the turbocompressor air turbine 146 to thereby drive the air turbine 146, and the cabin bleed offtakes 132, 134 are in fluid communication with the turbocompressor air compressor 148 such that air from the offtakes 132, 134 is compressed by the turbocompressor air compressor 148.

Abstract: A method of operating a gas turbine engine compressor. The method includes: determining an operating point of the compressor, and modulating mass flow of environmental control system input air to maintain the operating point of the gas turbine engine compressor within predetermined limits.

Abstract: A method of operating a gas turbine engine compressor. The method includes: determining an operating point of the compressor, and modulating mass flow of environmental control system input air to maintain the operating point of the gas turbine engine compressor within predetermined limits.

Abstract: A pneumatic system 131 for use with gas turbine engines 10 and aircraft 100. The pneumatic system 131 comprises a first engine core compressor bleed offtake in the form of an engine handling bleed offtake 140, and a second engine core compressor bleed offtake in the form of first and second cabin bleed offtake 132, 134, the handling bleed being configured to supply higher pressure air than the cabin offtakes 132, 134. The system 131 comprises a turbocompressor 144 comprising an air compressor 148 driven by a turbine 146. The handling bleed offtake 140 is in fluid communication with the turbocompressor air turbine 146 to thereby drive the air turbine 146, and the cabin bleed offtakes 132, 134 are in fluid communication with the turbocompressor air compressor 148 such that air from the offtakes 132, 134 is compressed by the turbocompressor air compressor 148.

Abstract: A bleed air system for an aircraft has a gas turbine engine and operating method. The system includes an environmental control system (ECS) for providing cabin airflow to the aircraft, including operating modes such as first and second air cycle machine operating modes and heat exchanger operating modes. The ECS includes first, second and third bleed ports each configured to provide engine bleed air from gas turbine engine compressors to the ECS. The ECS includes a bleed air system sensor arrangement configured to sense one or more bleed air system conditions, an environmental control system controller that selects an environmental control system operating mode that provides required cabin air flow and temperature at an optimal specific fuel consumption of the gas turbine engine at the sensed system conditions, and a bleed port valve controller which determines an operating pressure required to operate the environmental control system in the selected mode.