The Hall XPTBH was a prototype American twin-engined seaplane, submitted to the United States Navy by the Hall Aluminum Aircraft Corporation in response to a 1934 specification for new bomber and scout aircraft. Constructed in an innovative fashion that made extensive use of aluminum, the XPTBH proved successful in flight testing, but failed to win favor with the U.S. Navy. No production contract was awarded, and the single aircraft built served in experimental duties before its destruction in a hurricane during 1938. Design and development In late 1934, the U.S. Navy's Bureau of Aeronautics (BuAer) issued a specification for new scout bomber and torpedo bomber designs. Eight companies submitted a total of ten designs in response, evenly split between monoplanes and biplanes. The Hall Aluminum Aircraft Company submitted the only seaplane design; a single prototype was ordered by the Navy for evaluation on June 30, 1934. Given the designation XPTBH-1, it became the only aircraft to receive three mission-type letters under the U.S. Navy's designation system used between 1922 and 1962. Hall's choice of the twin-float seaplane configuration was dictated by the Navy's requirement that the new torpedo-bomber design should be capable of carrying a standard naval torpedo of the type carried by destroyers. As ordered, the XPTBH-1 was intended to be fitted with Wright R-1820 "Cyclone" radial engines; delays in design caused by Hall relocating their production facility, difficulties with the contract, and doubts about the aircraft's performance potential led to a redesign, the aircraft becoming slightly smaller and the engines being changed to a pair of Pratt & Whitney R-1830 "Twin Wasp" radials. The changes to the aircraft resulted in it receiving the revised designation XPTBH-2. Utilising Hall's standard aluminum tubular spar, the fuselage and wing leading edges were covered in aluminum, while the rest of the wing and the control surfaces were fabric-covered. The aircraft was well-armed defensively by 1930s standards, with a powered turret, designed by Hall, mounted in the nose and carrying a single .30-caliber machine gun. Hand-traversed mountings for a pair of machine guns were fitted in dorsal (top) and ventral (belly) positions aft. An optically flat glass panel was fitted in the nose below the turret for use by the bombardier; the aircraft's offensive weaponry, consisting of a Mark XIII aerial torpedo or, alternatively, up to of bombs, was carried in an internal bomb bay, the twin-float arrangement allowing for a clear release