Boeing B-9

The Boeing B-9 was the first all-metal monoplane bomber aircraft designed for the United States Army Air Corps. The first service model, dubbed the YB-9, was originally tested and developed by the United States aircraft manufacturing company Boeing as XB-901 and first flew on April 29, 1931. The YB-9 was an enlarged alteration of the Boeing 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 United States military. The air-cooled radial engine was lighter and more reliable than the liquid-cooled engine, and less vulnerable to enemy damage. 

The Y1B-9 was an improved version of the YB-9, featuring more powerful engines and a redesigned vertical stabilizer. Utilising two Pratt & Whitney R-1860-11 Hornet engines, the plane was faster than any contemporary fighter aircraft. The Y1B-9 was the first enclosed-cockpit plane flown by the Army. Its high speeds made open cockpits extremely impractical. Five were ordered by the Army in September 1931.

Boeing B-9
Class Aircraft
Type Bomber
Manufacturer Messerschmitt-Bolkow-Blohm (MBB)
Origin United States of America
Country Name Origin Year
United States of America 1931
ManufacturerName Production From Production To Quantity
Messerschmitt-Bolkow-Blohm (MBB) 1967 View

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 ft (88.6 m)
  • Empty weight: 8,941 lb (4,056 kg)
  • Loaded weight: 13,932 lb (6,320 kg)
  • Max takeoff weight: 14,320 lb (6,500 kg)
  • Powerplant: 2 x Pratt & Whitney R-1860-11 "Hornet" radial engine, 600 hp (450 kW) each


  • Maximum speed: 188 mph (163 knots, 302 km/h)
  • Cruise speed: 165 mph (143 knots, 265 km/h)
  • Range: 540 mi (470 nm, 870 km)
  • Service ceiling 20,750 ft (6,325 m)
  • Wing loading: 14.6 lb/ft (71.3 kg/m)
  • Power/mass: 0.0861 hp/lb (142 W/kg)


  • Guns: 2 x .30 in (7.26 mm) machine guns
  • Bombs: 2,200 lb (1,000 kg) bombs

End notes