Advanced method and aircraft for pre-cooling an environmental control system using a dual compressor four wheel turbo-machine

A method of providing bleed air to environmental control systems using a gas turbine engine, the method comprising:

• determining a bleed air demand for the environmental control systems;
• selectively supplying one of unconditioned low pressure bleed air or unconditioned high pressure bleed air along a first path extending between a compressor section of the gas turbine engine and a first turbine section of a turbo air cycle machine having multiple turbine sections and multiple compressor sections, with the first turbine section emitting a cooled air stream;
• selectively supplying unconditioned low pressure bleed air along a second path extending between the compressor section of the gas turbine engine and at least one of a first compressor section or a second compressor section of the turbo air cycle machine, with the at least one of the first compressor section or the second compressor section emitting a compressed air stream;
• selectively supplying the cooled air stream to a second turbine section of the turbo air cycle machine, with the second turbine section emitting a further cooled air stream;
• and
• combining at least one of the cooled air stream emitted from the first turbine section or the further cooled air stream emitted from the second turbine section with the emitted compressed air stream to form a conditioned air stream;
• wherein the selectively supplying unconditioned low pressure bleed air and unconditioned high pressure bleed air and selectively supplying the cooled air stream are controlled such that the conditioned air stream satisfies the determined bleed air demand.