Keystone B 5

Design and development

Three B-3A (LB-10A) were reengined with Wright R-1750-3 radial engines and were redesignated Y1B-5. The Army Air Corps changed the design of the last 27 LB-10As on order, replacing the Pratt & Whitney R-1690 radial engines with the Wright R-1750-3. The Pratt & Whitney-powered aircraft were designated B-3A, and the Wright-powered aircraft became B-5A. They provided the backbone of the U.S. bomber force from then to 1934.

Operational history

B-5A were first line bombers of the United States for the period between 1930 and 1934. Afterwards, they remained in service primarily as observation aircraft until the early 1940s.

Variants

LB-14

Designed as LB-10 with 575 hp (429 kW) Pratt & Whitney GR-1860 engines; three ordered, but redesigned with 525 hp (392 kW) Wright R-1750-3 engines and delivered as the Y1B-5.

Y1B-5

Three pre-production aircraft redesignated from LB-14 before delivery.

B-5A

Wright R-1750-3 version originally ordered as B-3A, 27 built

Operators

 United States

United States Army Air Corps

Specifications (B-5A)

General characteristics

Crew: 5

Length: 48 ft 10 in (14.9 m)

Wingspan: 74 ft 8 in (22.8 m)

Height: 15 ft 9 in (4.8 m)

Wing area: 1,145 ft² (106.4 m²)

Empty weight: 7,705 lb (3,945 kg)

Loaded weight: 12,952 lb (5,875 kg)

Max. takeoff weight: lb (kg)

Powerplant: 2 × Wright R-1750-3 radial engines, 525 hp (392 kW) each

Performance

Maximum speed: 111 mph (97 kn, 179 km/h)

Cruise speed: 98 mph (86 kn, 160 km/h)

Range: 815 mi (707 nmi, 1,310 km)

Service ceiling: 14,000 ft (4,270 m)

Wing loading: 273.3 lb/f² (52.22 kg/m²)

Power/mass: 0.0810 hp/lb (133 W/kg)

Armament

Guns: 3 × .30 in (7.62 mm) Browning machine guns

Bombs: 2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs