Editing Keystone B-4

{{short description|American bomber aircraft}}
<!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. -->
{{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<br />25 B-4A
 |unit cost=
 |developed_from=[[Keystone B-3]]
 |variants=
}}

The '''Keystone B-4''' was a [[biplane]] [[bomber aircraft|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 [[Keystone B-3|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-10|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 [[Keystone B-6|Y1B-6]] with different engine installations.
;Y1B-4
:Five pre-production aircraft, as the [[Keystone B-3|LB-10]] but with two 575&nbsp;hp (429&nbsp;kW) [[Pratt & Whitney R-1860-7]] engines.
;B-4A
:Production version of the Y1B-4, 25 built.

==Operators==
;{{flag|United States|1912}}
*[[United States Army Air Corps]]

==Specifications (B-4A)==
[[File:28th Bombardment Squadron Keystone B-4A in in the Philippines.jpg|thumb|right|Keystone B-4A in flight in the Philippines]]
{{Aircraft specs
    |ref                        = <!-- reference --> 
    |prime units?               = imp
    <!-- imp or kts first for US aircraft, and UK aircraft pre-metrification, 
    met(ric) first for all others. You MUST choose a format, or no specifications will show -->
    <!--General characteristics-->
    |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           = 
    <!--Powerplant-->
    |eng1 number            = 2
    |eng1 name              = [[Pratt & Whitney R-1860]]-7
    |eng1 type              = [[radial engine]]s
    |eng1 kw                = <!-- prop engines --> 429
    |eng1 hp                = <!-- prop engines --> 575
    |eng1 shp               = <!-- prop engines --> 
    |eng1 kn                = <!-- jet/rocket engines --> 
    |eng1 lbf               = <!-- jet/rocket engines --> 
    |power original         = 
    |thrust original        = 
    |eng1 kn-ab             = 
    |eng1 lbf-ab            = 
    |more power             = 
    |prop name              = 
    |prop dia m             = <!-- propeller aircraft --> 
    |prop dia ft            = <!-- propeller aircraft --> 
    |prop dia in            = <!-- propeller aircraft --> 
    |rot dia m              = <!-- helicopters --> 
    |rot dia ft             = <!-- helicopters --> 
    |rot dia in             = <!-- helicopters --> 
    |rot area sqm           = <!-- helicopters --> 
    |rot area sqft          = <!-- helicopters --> 
    |rot number             = 
    <!--Performance-->
    |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       = 
    |combat range note      = 
    |ferry range km         = 
    |ferry range miles      = 
    |ferry range nmi        = 
    |ferry range note       = 
    |endurance              = <!-- if range unknown --> 
    |ceiling m              = 4300
    |ceiling ft             = 14000
    |ceiling note           = 
    |climb rate ms          = 30
    |climb rate ftmin       = 580
    |climb rate note        = 
    |sink rate ms           = <!-- sailplanes --> 
    |sink rate ftmin        = <!-- sailplanes --> 
    |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       = 
    <!--Armament-->
    
    |guns                   = 3 × .30 in (7.62 mm) [[Browning Arms Company|Browning]] [[machine gun]]s
    |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=
* [[Keystone B-3]]
* [[Keystone B-5]]
* [[Keystone B-6]]
|similar aircraft=
|lists=
* [[List of bomber aircraft]]
* [[List of military aircraft of the United States]]
}}

==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}}

[[Category:Keystone aircraft|B-4]]
[[Category:Light bombers]]
[[Category:1930s United States bomber aircraft|Keystone B-04]]
[[Category:Biplanes]]
[[Category:Twin piston-engined tractor aircraft]]
[[Category:Aircraft with fixed conventional landing gear]]