Aircraft on board inert gas generation system

The system, e.g. for providing inert gas to aircraft fuel tanks52, receives air from a relatively low pressure source such as low pressure engine bleed air or ram air and comprises a compressor 40, e.g. a positive displacement compressor for supplying an air separation module 48. All or a portion of the compressed air from the compressor 40 may be supplied via a line 82 to one or more other aircraft components to provide at least one of power, heat and pressure thereto, e.g. anti-icing elements 84, 86 for wings or engine inlets, cabin toilet flushing, pressurizing water tanks, pneumatic actuators for thrust reversers, or assisting engine starting. A controller 80 controls a motor 58 for the compressor 40 and a downstream check valve 60 to provide the flow diversion; the controller can vary the compressor speed to vary the compressed air flow temperature. In a multi-stage compressor arrangement, the flow diversion is after the first stage.