Bleed air systems for use with aircraft and related methods

An aircraft comprising:

• a gas turbine engine including a low-pressure compressor and a combustor downstream from the low-pressure compressor;
• a fan disposed upstream from the low-pressure compressor, the fan mechanically coupled to, and driven by, the gas turbine engine;
• a turbo-compressor including:
• a compressor having a compressor inlet fluidly coupled to the low-pressure compressor of the gas turbine engine and a compressor outlet fluidly coupled to a system of the aircraft;
• and
• a turbine operatively coupled to the compressor to selectively drive the compressor;
• a gearbox operatively coupled to the turbo-compressor;
• and
• a clutch disposed between the turbo-compressor and the gearbox to selectively connect the turbo-compressor to the gearbox to enable the gas turbine engine to drive the turbo-compressor.

A method comprising:

• coupling a first drive shaft of a turbo-compressor to a gearbox via a clutch, the turbo-compressor comprising a compressor and a turbine operatively coupled via the first drive shaft, the first drive shaft to enable the turbine to selectively drive the compressor;
• coupling the gearbox to a second drive shaft extending from an aircraft engine;
• fluidly coupling a compressor outlet of the compressor to a system of an aircraft that is to receive pressurized air;
• fluidly coupling a compressor inlet of the compressor to a bleed air port of a low-pressure compressor of the aircraft engine;
• and
• using the clutch to selectively connect the first drive shaft to the gearbox to enable the second drive shaft to power the compressor to supply pressurized air to the system.