Abstract: The present invention relates to a wing motor of the type suitable for use in down-hole drilling applications. The motor comprises a generally tubular casing 1, 2 and a rotor 4 mounted for rotation within the casing 1, 2 with a chamber 18 therebetween. The casing 1, 2 is provided with angularly spaced apart inlets and outlets 19, 20 for ingress of pressurized working fluid from an inlet conduit 19a in the casing 1, 2 into the chamber 18 and egress of the fluid to an outlet conduit 20a separated from inlet conduit 19a by a wall 21. The casing 1, 2 has a generally radially extending wall 3 extending more or less into contact with the rotor 4 at an angular position between the outlet 20 and the inlet 19.