AIRCRAFT AIR CONDITIONING SYSTEM AND METHOD OF OPERATING AN AIRCRAFT AIR CONDITIONING SYSTEM

An aircraft air conditioning system (10) comprises an ambient air supply line (12) having a first end connected to an ambient air inlet (14) and a second end connected to a mixer (16) of the aircraft air conditioning system (10) so as to supply ambient air to the mixer (16). A first compressor (18) is arranged in the ambient air supply line (12) and is adapted to compress the ambient air flowing through the ambient air supply line (12). A bleed air supply line (52) allows a flow of bleed air bled off from an engine (54) or an auxiliary power unit therethrough. A bleed air turbine (60) is driven by the bleed air flowing through the bleed air supply line (52) and is coupled to the first compressor (18) so as to drive the first compressor (18).