Keystone B-3

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

Design and development
It 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 its safety, it was far superior to its oldest predecessors.

Operational history
The B-3A was the last biplane 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.

Variants

 * 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 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, both wingspan and fuselage. a total of 63 were ordered (S/N 30-281/343). It was re-designated as the B-3A before any deliveries were made, and the final 27 were built as B-5A.


 * B-3A
 * 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).

Operators

 * 🇺🇸 United States
 * United States Army Air Corps
 * 2d Bombardment Group, Langley Field, Virginia
 * 20th Bomb Squadron - operated B-3A and B-5A 1931-1932
 * 49th Bomb Squadron - operated B-3A and B-5A 1931-1932
 * 96th Bomb Squadron - operated B-3A and B-5A 1931-1932
 * 4th Composite Group, Nichols Field, Luzon, Philippines
 * 28th Bomb Squadron - operated B-3A 1932-1937
 * 2nd Observation Squadron- operated B-3A 1938-1940
 * 5th Composite Group, Luke Field, Territory of Hawaii
 * 23d Bomb Squadron - operated B-5A 1932-1937
 * 72d Bomb Squadron - operated B-5A 1932-1936
 * 6th Composite Group, France Field, Panama Canal Zone
 * 25th Bomb Squadron - operated B-3A 1932-1936
 * 7th Bombardment Group, March Field, California
 * 9th Bomb Squadron - operated B-3A 1931-1934
 * 11th Bomb Squadron - operated B-3A 1931-1934
 * 31st Bomb Squadron - operated B-3A 1931-1934
 * 19th Bombardment Group, Rockwell Field, California
 * 30th Bomb Squadron - operated B-3A 1932-1936
 * 32d Bomb Squadron - operated B-3A 1932-1935
 * Air Corps Advanced Flying School, Kelly Field, Texas
 * 42d Bomb Squadron - operated B-3A and B-5A 1935-1936
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 * Philippine Army Air Corps
 * 10th Bombardment Squadron