The Boeing Y1B-9A was an early monoplane bomber originally developed as a private venture in 1930-31 but that failed to gain any production orders.
Work on the aircraft began as a private venture in 1930. Boeing based their new bomber on their Model 200 Monomail, a cantilever wing single-engined semi-monocoque aircraft with a semi-retractable undercarriage and anti-drag cowling. The new bomber was essentially a scaled-up version of the same design. Boeing began work on two prototypes, the Model 214 and Model 215.
The main changes on the new aircraft was the increase in size, the change from one to two engines (with the engines carried in nacelles on the wing leading edge) and an expanded fuselage with space for a crew of five. The prototype was powered by two 575hp Pratt & Whitney R-1860-13 Hornet radial engines. The Model 215 was something of a transitional design, and this was best seen in the crew positions. The radio operator had a cabin within the fuselage but the other four crew members sat in individual open cockpits dotted along the top of the fuselage. The bomb-aimer/ nose gunner was at the front. The radio operator was behind him, inside the fuselage. Next came the pilot and co-pilot in open cockpits above the wing leading edge, and finally the rear gunner behind the wings. The aircraft could carry 2,260lb bombs, split between an internal bomb bay and under-wing racks.
The Model 215 made its maiden flight on 13 April 1931. It was tested by the USAAC as the XB-901, then procured as the YB-9. The Army also placed a contract to buy the incomplete Model 214, as the Y1B-9 and five service test aircraft. These were given the Boeing model number 246 and the Army designation Y1B-9A.
The Model 214 was powered by two 600hp Curtiss V-1570-29 Conqueror inline engines when it made its maiden flight on 5 November 1931. It was then re-engined with supercharged Hornet engines.
The five Y1B-9As got the same supercharged engines. They also had a new vertical tail structure and a number of internal changes. The first Y1B-9A made its maiden flight on 14 July 1932.
The Boeing bomber was then evaluated against the Martin Model 123. Martin won, and their aircraft entered service as the Martin B-10. Boeing did gain valuable experience in the design of bombers from the B-9 programme, some of which became valuable during the development of the B-17 Flying Fortress.
Y1B-9A (Model 246)
Engine: Two Pratt & Whitney SR-1860-11 supercharged radial piston engines
Power: 600hp each
Span: 76ft 10in
Length: 51ft 9in
Height: 12ft 0in
Empty Weight: 8,941lb
Normal Loaded Weight: 13,608lb
Maximum Take-off Weight: 14,320lb
Maximum Speed: 186mph at 6,000ft
Cruising Speed: 165mph
Range: 540 mile radius, 1,250 miles ferry range.
Guns: Two flexibly mounted 0.3in machine guns, one in front cockpit and one in rear cockpit
Bomb load: 2,260lb