Keystone B-4

Infobox Aircraft
name=B-4


caption=Keystone Y1B-4 (S/N 30-281).
type=Light bomber
manufacturer=Keystone
designer=
first flight=
introduced=
retired=
status=
primary user=United States Army Air Corps
more users=
produced=
number built= 5 Y1B-4
25 B-4A
unit cost=
developed from=Keystone B-3
variants with their own articles=

The Keystone B-4 was a biplane bomber produced 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 that funds for the design did not come from the normal annual funds.)

The first B-3A (S/N 30-281) was converted to Y1B-4 configuration with the addition of 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, but the only difference between the two planes were their engines. On April 28, 1931, 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 (along with 39 B-6As, dientical in all respects except their make of engine), and the B-4As, delivered between January and April of 1932, were the last biplane bombers delivered to the Air Corps.

Operational history

B-4 was the last of the Keystone biplane bombers 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 went into operational service. 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

;flag|United States|1912
*United States Army Air Corps

pecifications (B-4A)

aircraft specifications

plane or copter?=plane
jet or prop?=prop

crew=5
length main=48 ft 10 in
length alt=14.9 m
span main=74 ft 8 in
span alt=22.8 m
height main=15 ft 9 in
height alt=4.8 m
area main=1,145 ft²
area alt=106.4 m²
empty weight main=7,951 lb
empty weight alt=3,607 kg
loaded weight main=12,952 lb
loaded weight alt=5,875 kg
max takeoff weight main= lb
max takeoff weight alt= kg

number of props=2
engine (prop)=Pratt & Whitney R-1860-7
type of prop=radial engines
power main=575 hp
power alt=429 kW

max speed main=130 mph
max speed alt=110 kn, 210 km/h
cruise speed main=103 mph
cruise speed alt=90 kn, 167 km/h
range main=850 mi
range alt=760 NM, 1,400 km
ceiling main=14,000 ft
ceiling alt=4,300 m
climb rate main=580 ft/min
climb rate alt=30 m/s
loading main=11.31 lb/ft²
loading alt=55.22 kg/m²
power/mass main=0.0888 hp/lb
power/mass alt=146 W/kg

guns=3× .30-calibre (7.62 mm) Browning machine guns
bombs=2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs

References and external links

* [http://home.att.net/~jbaugher2/b4.html Encyclopedia of American Aircraft]
* [http://www.aerofiles.com/keys-b4a.jpgPhotograph]
* [http://www.wpafb.af.mil/museum/research/bombers/b1-45.htm USAF Museum article on B-4]
* [http://www.wpafb.af.mil/museum/research/bombers/b1-33.htm USAF Museum article on LB-13]

ee also

aircontent

related=
* Keystone B-3
* Keystone B-5
* Keystone B-6

similar aircraft=

lists=
* List of bomber aircraft
* List of military aircraft of the United States