The Curtiss/Curtiss-Robertson Model 56 Thrush was a 1929 six passenger high-wing fixed undercarriage single-engine cabin monoplane airliner and utility transport powered by either a Curtiss Challenger or a Wright Whirlwind radial engine and built as an enlargement of the earlier Curtiss Robin. Several were used for record breaking endurance flights by female pilots during the early 1930s including one in which the aircraft stayed aloft for almost ten days. Three 170 hp (130 kW) Curtiss Challenger-engined Curtiss Thrush prototypes (serialled G-1 to G-3) were built at Curtiss' Garden City factory, but these were underpowered and production examples, redesignated Thrush J (serialled 1001 to 1010) with 225 hp (168 kW) Wright Whirlwind engines, were built at the Curtiss-Robertson St Louis factory. All three prototypes were later re-engined with Whirlwinds to make them Thrush Js. The fuselage of the Thrush formed the basis for the twin-engine Curtiss Kingbird which was developed roughly in parallel. The fuselage was built up as a Pratt truss frame formed mainly from Duraluminum tubing and fittings with welded Chrome-moly tubing reinforcing highly stressed areas and covered in fabric. The wing was a fabric covered semi-cantilever braced with steel tube struts, and had solid spruce spars and stamped Alclad ribs with Alclad sheet wrapped over leading edge. A fuel tank is mounted within each wing near the root. Rudder and elevators were welded chrome-moly steel tubing. 116" track undercarriage is fitted with oleo-pneumatic shock obsorbers and Bendix brakes, and is braced to the front struts and lower longerons. Noumber built: 13. Variants Thrush (ATC 159 & 160) - prototypes powered by 170 hp Curtiss Challenger, three built, all converted to Thrush J (ATC 236). Thrush J (ATC 261) - main production variant with 225 hp Wright J-6-7 Whirlwind, 10 built. Thrush Special - one converted from a Thrush J with 240 hp Wright J-6-7 Whirlwind. and a second converted with Wright J-5.
