A method of operating an electric power generation system comprising a turbo-prop engine, a reduction gear box and a propeller system, the propeller system comprising: a propeller shaft driven by the turbo-prop engine through the reduction gear box, a propeller hub attached to and driven by the propeller shaft to rotate about an axis, and including two or more blade attachments that house propeller blades, a generator concentrically enclosed within the propeller hub, the generator comprising a plurality of first and second generator parts, wherein the plurality of first generator parts are connected to the propeller hub, a gear assembly concentrically enclosed within the propeller hub and rotatably attached to the second generator parts, wherein the gearing assembly is configured to allow relative rotation between the first and second generator parts caused by the propeller hub; the method comprising: - generating electric power by rotating the propeller hub about the axis such that the plurality of first generator parts rotate relative to the plurality of second generator parts; - when the propeller system is driven by the output of turbo-prop engine transmitted through the reduction gear box: using the generated electric power to power an actuation system to change the pitch of the propeller blades; - when the propeller system is windmilling: using the generated electric power to restart the turbo-prop engine during flight or to provide power during an engine failure. a propeller shaft driven by the turbo-prop engine through the reduction gear box, a propeller hub attached to and driven by the propeller shaft to rotate about an axis, and including two or more blade attachments that house propeller blades, a generator concentrically enclosed within the propeller hub, the generator comprising a plurality of first and second generator parts, wherein the plurality of first generator parts are connected to the propeller hub, a gear assembly concentrically enclosed within the propeller hub and rotatably attached to the second generator parts, wherein the gearing assembly is configured to allow relative rotation between the first and second generator parts caused by the propeller hub; the method comprising: - generating electric power by rotating the propeller hub about the axis such that the plurality of first generator parts rotate relative to the plurality of second generator parts; - when the propeller system is driven by the output of turbo-prop engine transmitted through the reduction gear box: using the generated electric power to power an actuation system to change the pitch of the propeller blades; - when the propeller system is windmilling: using the generated electric power to restart the turbo-prop engine during flight or to provide power during an engine failure. - generating electric power by rotating the propeller hub about the axis such that the plurality of first generator parts rotate relative to the plurality of second generator parts; - when the propeller system is driven by the output of turbo-prop engine transmitted through the reduction gear box: using the generated electric power to power an actuation system to change the pitch of the propeller blades; - when the propeller system is windmilling: using the generated electric power to restart the turbo-prop engine during flight or to provide power during an engine failure.