Boeing 214 Y1B-9
Boeing 215 XB-901 YB-9
Boeing 246 Y1B-9A
In 1930 Boeing began the private-venture development of a bomber aircraft based on the Model 200 Monomail. The resulting prototypes and service evaluation bombers were scaled-up versions of this aircraft. They differed by having twin-engines, installed in nacelles at the wing leading edge, and by adaptation of the fuselage to cater for the crew and weapons.
To provide the crew accommodation, the fuselage was extended forward of the wing. A bomb-aimer/gunner was accommodated in the nose and immediately behind him, within the fuselage, was a radio operator's position. Aft of the radio operator were two cockpits in tandem, for pilot and co-pilot, with a fourth open cockpit, just aft of the wing trailing edge, for the rear gunner. A bombload totalling 1025kg could be divided between an internal bomb bay and underwing racks.
First flying, on 13 April 1931, was the Boeing Model 215, powered by two 429kW Pratt & Whitney R-1860-13 Hornet radials. This was tested by the USAAC under the initial designation XB-901 (Experimental Bomber), and satisfactory conclusion of testing resulted in the procurement of this aircraft under the designation YB-9. At the same time the then incomplete Boeing Model 214 was contracted under the designation Y1B-9, plus five additional service test aircraft with the designation Y1B-9A (Model 246).
The Model 214, powered by 447kW Curtiss V-1570-29 Conqueror inline engines, was flown for the first time on 5 November 1931, and following further tests, the Model 214 was re-engined with a supercharged version of the Pratt & Whitney Hornet. This power-plant was chosen also for the Y1B-9As, the first of which was flown on 14 July 1932. The Y1B-9A differed externally from the earlier prototypes in having modified vertical tail surfaces, and had internally a number of equipment and structural changes to meet service requirements.
Subsequent testing, and evaluation against the Martin Model 123, resulted in the Martin aircraft entering service as the B-10. This came as a great disappointment to the Boeing company, which had produced this bomber with performance superior to most contemporary fighter aircraft.
Boeing 215 / XB-901 / YB-9
Engines: 2 x Pratt & Whitney R-1860-13 Hornet radials, 429kW
Boeing 214 / Y1B-9
Engines: 2 x Curtiss V-1570-29 Conqueror inline, 447kW
re-engined with 2 x 447kW Pratt & Whitney SR-1860-11 Hornetsupercharged radial piston
Boeing 246 / Y1B-9A
Engine: 2 x Pratt & Whitney SR-1860-11 Hornet, 447kW / 600 hp
Take-off weight: 6495 kg / 14319 lb
Empty weight: 4056 kg / 8942 lb
Wingspan: 23.42 m / 76 ft 10 in
Length: 15.77 m / 51 ft 9 in
Height: 3.66 m / 12 ft 0 in
Wing area: 88.63 sq.m / 954.00 sq ft
Max. speed: 299 km/h / 186 mph / 163kt
Cruise speed: 266 km/h / 165 mph
Ceiling: 6325 m / 20750 ft
Rate-of-Climb: 900ft/min (274m/min)
Range: 869 km / 540 miles
Armament: 2-4 x 0.30 caliber machine guns
Accommodation: 4 or 5