An air driven turbine having variable pitched blades is provided that includes a pitch change mechanism for adjusting the pitch of the blades during either rotating or non-rotating operational modes of the air driven turbine. The pitch control mechanism includes a resettable overspeed protection device which is directly actuated by an overspeed condition of the turbine and operates independently from the pitch change mechanism to move the blades to a failsafe, feathered, or coarse pitch, low speed position. The pitch control mechanism utilizes a linear actuator in the form of an acme screw drive. The air driven turbine includes a ball ramp thrust bearing for attaching the blades to a hub of the turbine in such a manner that during rotation of the turbine actuation loads on the pitch change mechanism are reduced.