An air pump or blower in the intake system of an internal combustion engine. Its purpose is to increase the air-charge weight and therefore the power output from an engine of a given size. In an aircraft engine, the supercharger counteracts the power loss that results from the decrease of atmospheric pressure with increase of altitude. Various types of pumps and compressors may be used as superchargers, which are either mechanically driven by the engine crankshaft or powered by the engine exhaust gas.