Boeing XPW-9 Pursuit Fighter Prototype with Tunnel Radiator (Circa 1923)

A front three-quarter view of an experimental military pursuit biplane with a large pointed nose spinner, tunnel radiator, and heavy wheel chocks. — Boeing XPW-9 Pursuit Fighter Prototype with Tunnel Radiator (Circa 1923) · Donald A. Hall Estate Collection

A detailed technical perspective of the Boeing Model 15 (XPW-9) pursuit prototype at McCook Field, captured from the front three-quarter angle. Donald A. Hall Sr. framed the aircraft to highlight its massive pointed aerodynamic propeller spinner, Curtiss D-12 liquid-cooled engine with upper cowl exhaust stubs, underslung tunnel radiator with face shutters, and heavy wooden safety chocks. Hall analyzed these exact drag-reduction and cooling innovations before applying high-efficiency aerodynamic cowlings to the Ryan NYP Spirit of St. Louis.