Gas turbine engine assembly

A generator assembly for a gas turbine engine (10). The assembly includes an electrical generator (32) connected via a first sprag clutch (34) to an accessory gearbox (22) driven by the engine (10). The generator (32) is also connected by a second sprag clutch (36) to an air turbine (38) connected to engine bleed valves (12) which are selectively open when the engine speed falls below a predetermined level. The clutches (34,36) are arranged such that the generator (32) is driven at any time by the fastest rotating of the gearbox (22) and turbine (38).