boeing y1b-9

Maximum speed: 188 mph (302 km/h)
Cruising speed: 165 mph (264 km/h)
Combat Range: 540 miles (868 km)
Service ceiling: 20,750 ft (6,324 m)
Wing loading: lb/ft&sup2; ( kg/m&sup2;)
Power/Mass: 0.0861 hp/lb (0.142 kW/kg)

The Boeing B-9 was the first all-metal monoplane bomber designed for the United States Army Air Corps. The first service model, dubbed the YB-9, was originally tested and developed by Boeing as XB-901. The YB-9 was an enlarged alteration of Boeing's Model 200 Commercial Transport. The Pratt & Whitney R-1830-13 radial engines used on the YB-9 gave it a top speed of 163 mph (262 km/h). The second test model, named the Y1B-9 (Y1B- indicating funding outside normal fiscal year procurement), used liquid-cooled Curtiss V-1570-29 'Conqueror' engines. The increased power from these engines, combined with increased streamlining of the engine nacelles, increased its top speed to 173 mph (278 km/h). With the exception of the B-2 Condor, liquid-cooled engines were never used on production bombers for the US military. The air-cooled radial engine was simpler and more reliable than the liquid-cooled engine, and less vulnerable to enemy damage. The Y1B-9A was an improved version of the YB-9, featuring more powerful engines and a redesigned vertical stabiliser. Utilising two Pratt & Whitney R-1860-11 'Hornets', the plane was faster than any contemporary Pursuit aircraft. The Y1B-9 was the first closed-cockpit plane flown by the Army. Its high speeds made open cockpits extremely impractical.