Keystone B-4
{{short description|American bomber aircraft}}
{{Infobox aircraft
|name=B-4
|image=Keystone Y1B-4 (SN 30-281).jpg
|caption=Keystone Y1B-4 (S/N 30-281)
|type=Light bomber
|manufacturer=Keystone Aircraft
|designer=
|first_flight=
|introduction=
|retired=
|status= Retired
|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=
}}
The Keystone B-4 was a biplane bomber, built by the Keystone Aircraft company 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 was 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, identical in all respects except their make of engine), and the B-4As, delivered between January and April 1932, were the last biplane bombers delivered to the Air Corps.
Operational history
The 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 575 hp (429 kW) Pratt & Whitney R-1860-7 engines.
;B-4A
:Production version of the Y1B-4, 25 built.
Operators
;{{flag|United States|1912}}
Specifications (B-4A)
File:28th Bombardment Squadron Keystone B-4A in in the Philippines.jpg
{{Aircraft specs
|ref =
|prime units? = imp
|crew = 5
|capacity =
|length m = 14.9
|length ft = 48
|length in = 10
|span m = 22.8
|span ft = 74
|span in = 8
|height m = 4.8
|height ft = 15
|height in = 9
|wing area sqm = 106.4
|wing area sqft = 1145
|aspect ratio =
|airfoil =
|empty weight kg = 3607
|empty weight lb = 7951
|gross weight kg = 5875
|gross weight lb = 12952
|max takeoff weight kg =
|max takeoff weight lb =
|more general =
|eng1 number = 2
|eng1 name = Pratt & Whitney R-1860-7
|eng1 type = radial engines
|eng1 kw = 429
|eng1 hp = 575
|eng1 shp =
|eng1 kn =
|eng1 lbf =
|power original =
|thrust original =
|eng1 kn-ab =
|eng1 lbf-ab =
|more power =
|prop name =
|prop dia m =
|prop dia ft =
|prop dia in =
|rot dia m =
|rot dia ft =
|rot dia in =
|rot area sqm =
|rot area sqft =
|rot number =
|max speed kmh = 210
|max speed mph = 130
|max speed kts = 110
|max speed note =
|max speed mach =
|cruise speed kmh = 167
|cruise speed mph = 103
|cruise speed kts = 90
|cruise speed note =
|stall speed kmh =
|stall speed mph =
|stall speed kts =
|stall speed note =
|never exceed speed kmh =
|never exceed speed mph =
|never exceed speed kts =
|range km = 1400
|range miles = 850
|range nmi = 760
|range note =
|combat range km =
|combat range miles =
|combat range nmi =
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|ferry range km =
|ferry range miles =
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|endurance =
|ceiling m = 4300
|ceiling ft = 14000
|ceiling note =
|climb rate ms = 30
|climb rate ftmin = 580
|climb rate note =
|sink rate ms =
|sink rate ftmin =
|sink rate note =
|wing loading kg/m2 = 55.22
|wing loading lb/sqft = 11.31
|disk loading kg/m2 =
|disk loading lb/sqft =
|power/mass = 0.0888 hp/lb (146 W/kg)
|thrust/weight =
|more performance =
|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
|rockets =
|missiles =
|hardpoints =
|hardpoint capacity =
|hardpoint rockets =
|hardpoint missiles =
|hardpoint bombs =
|hardpoint other =
|avionics = }}
See also
{{Aircontent
|related=
|similar aircraft=
|lists=
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External links
{{commons category|Keystone B-4}}
- [https://web.archive.org/web/20050301053131/http://home.att.net/~jbaugher2/b4.html Encyclopedia of American Aircraft]
- [http://www.aerofiles.com/keys-b4a.jpg Photograph]
- [https://web.archive.org/web/20040804111311/http://www.wpafb.af.mil/museum/research/bombers/b1-45.htm USAF Museum article on B-4]
- [https://web.archive.org/web/20040813193626/http://www.wpafb.af.mil/museum/research/bombers/b1-33.htm USAF Museum article on LB-13]
{{Keystone aircraft}}
{{USAF bomber aircraft}}