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Keystone B-4

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B-4
Keystone Y1B-4 (S/N 30-281).
Type Light bomber
Manufacturer Keystone
Primary user United States Army Air Corps
Number built 5 Y1B-4 + 25 B-4A
Developed from Keystone B-3

The Keystone B-4 was a biplane bomber developed for the United States Army Air Corps.

Design and development

Originally ordered by the United States Army Air Corps as the LB-13 (light bomber), when the LB- designation was dropped in 1930, the first five planes were redesignated Y1B-4. (The Y1B- designation indicates funding outside the the normal annual appropriation.)

The first B-3A (S/N 30-281) was converted to Y1B-4 configuration with the addition of more powerful R-1860-7 radial engines and low pressure tires. Because of more powerful engines, the performance of the Y1B-4 was a slight improvement on the B-3. In 1932, the army ordered 25 improved Y1B-4s as the Keystone B-4A. This production version was part of the last biplane bomber order made by the Army Air Corps.

Operational history

The B-4 was the last Keystone model ordered by the U.S. Army in late 1931. These aircraft were used primarily as observation and reconnaissance aircraft as early as 1934 when the Martin B-10B became operational. Some remained in service into the early 1940s.

Variants

LB-13
Seven aircraft ordered but delivered as the Y1B-4 and Y1B-6 with different engine installations.
Y1B-4
Five pre-production aircraft, as the LB-10 but with two 575hp (429kW) R-1860-7 engines.
B-4A
Production version of the Y1B-4, 25 built.

Operators

Template:Country data United States

Specifications (B-4A)

File:060421-F-1234P-010.jpg
Keystone B-4A in flight in the Philippines

General characteristics

Performance

Armament

  • Guns: 3× .30 (7.62 mm) Browning machineguns
  • Bombs: 2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs


References and external links

See also

Related development

Related lists

Template:USAF bomber aircraft


This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Keystone B-4".