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Keystone B-3

Bomber aircraft family by Keystone

Wikipedia contributorsAdapted for Fathomly · View authors
2 min read
Source updated August 26, 2026
Image credit is listed at the end of this article.

The Keystone B-3A was a bomber aircraft developed for the United States Army Air Corps by Keystone Aircraft in the late 1920s.

01Design and development

The B-3 was originally ordered as the LB-10A (a single-tail modification of the Keystone LB-6), but the Army dropped the LB- 'light bomber' designation in 1930.

Although the performance of the B-3A was hardly better than that of the bombers flown at the end of World War I, it had come a long way in terms of flight safety.

02Operational history

The B-3A was a member of the last family of biplanes operated by the US Army; it remained in service until 1940. A few years after it was first produced, the introduction of all-metal monoplanes rendered it almost completely obsolete.

03Variants

LB-10
The last of the 17 LB-6s ordered (S/N 29-27) was converted with a re-designed single fin and rudder and two 525 hp Wright R-1750E engines. Delivered to Wright Field on 7 July 1929, it was wrecked on 12 November 1929.
LB-10A
This version used Pratt and Whitney R-1690-3 Hornet engines and was slightly smaller, in both wingspan and length. A total of 63 were ordered (S/N 30-281/343). All were re-designated as the B-3A before any deliveries were made, with the final 27 built as B-5A with Wright engines.
B-3A
Ordered as LB-10A, 36 delivered as B-3A (S/N 30-281/316). The first aircraft was delivered in October 1930.
B-5A
Ordered as B-3A, re-engined with Wright R-1750-3 Cyclone engines, 27 built (S/N 30-317/343).

04Operators

United States
Philippines

05Specifications (B-3A)

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 sq ft (106.4 m2)
  • Empty weight: 7,705 lb (3,495 kg)
  • Gross weight: 12,952 lb (5,875 kg)
  • Powerplant: 2 × Pratt & Whitney R-1690-3 radial engines, 525 hp (392 kW) each

Performance

  • Maximum speed: 114 mph (183 km/h, 98 kn)
  • Cruise speed: 98 mph (158 km/h, 85 kn)
  • Range: 860 mi (1,400 km, 760 nmi)
  • Service ceiling: 12,700 ft (3,870 m)
  • Rate of climb: 530 ft/min (2.7 m/s)
  • Wing loading: 11.31 lb/sq ft (55.42 kg/m2)
  • Power/mass: 0.0811 hp/lb (133 W/kg)

Armament

  • Guns: 3 × .30 in (7.62 mm) machine guns
  • Bombs: 2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs
Watch videos about Keystone B-3Explainers and documentaries on YouTube (opens in a new tab)

Sources and credits

This article is adapted from the Wikipedia article “Keystone B-3”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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