Boeing Y1B-9
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.
Specifications (Y1B-9A) General Characteristics Crew: 4 Length: 51 ft 6 in (15.7 m) Wingspan: 76 ft 10 in (23.4 m) Height: 12 ft 8 in (3.86 m) Wing area: 954 ft² (88.6 m²) Empty: 8,941 lb (4,056 kg) Loaded: 13,932 lb (6,320 kg) Maximum takeoff: 14,320 lb (6,496 kg) Powerplant: 2× Pratt & Whitney R-1860-11 'Hornets' of 600 hp (450 kW) each
Performance 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: 14.6 lb/ft² (71.3 kg/m²) Power/Mass: 0.0861 hp/lb (0.142 kW/kg)
Armament 2× .30-calibre (7.26 mm) Browning machine guns 2,200 lb (1,000 kg) bombs
Links Wagner, Ray (1982). American Combat Planes. New York: Doubleday. ISBN 0930083172. Alain Pelletier (2002) "End of the Dinosaurs: Boeing's B-9, Breaking the Bomber Mold". Air Enthusiast 101. Encyclopedia of American aircraft USAF Museum article on the Y1B-9
Related Content
Comparable aircraft:
Martin B-10 Designation sequence:
B-6 -
Y1B-7 -
XB-8 -
Y1B-9 -
B-10 -
YB-11 -
B-12 Related Lists:
List of military aircraft of the United States -
List of bomber aircraft
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