In a stator of a vehicle ac generator, a stator core has plurality of slots, each of which has a rectangular cross-section and a stator winding formed of a plurality of U-shaped conductor segments made of a round wire. The two configurations are compared to determine maintenance services to be performed on the aircraft engine. The fluid directing structure has a plurality of individual inlet openings spaced around its periphery and is arranged to direct air at each inlet opening into an inner pipe. The premix fuel nozzle includes a plurality of coaxial passages, which provide gaseous fuel and compressed air to the fin assembly.