View source for Yokosuka B4Y

{{Short description|Japanese carrier-borne torpedo bomber}}
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{{Infobox aircraft
 |name= B4Y1
 |image=96siki-kankou.jpg
 |caption=
 |type= [[Torpedo bomber]]
 |manufacturer= [[Yokosuka Naval Air Technical Arsenal|Yokosuka]]
 |designer=
 |first_flight= [[1935 in aviation|1935]]
 |introduction= [[1936 in aviation|1936]]
 |retired= [[1943 in aviation|1943]]
 |status= 
 |more_users=
 |produced=
 |number_built= 205
 |unit cost=
 |variants=
}}

The '''Yokosuka B4Y''' (Navy Type 96 Carrier Attack Bomber) was a [[Aircraft carrier|carrier]]-borne [[torpedo bomber]] used by the [[Imperial Japanese Navy Air Service]] from 1936 to 1943. The B4Y replaced the [[Mitsubishi B2M|Mitsubishi B2M2]] and the [[Yokosuka B3Y]], and was the last [[biplane]] [[bomber]] used operationally by the [[Imperial Japanese Navy]]. The [[World War II Allied names for Japanese aircraft|Allied reporting name]] was "'''Jean'''". This aircraft was mistakenly identified by the British as the Nakajima Navy G-96.{{Sfn | Lawrence | 1945 | p =  194}}

==Design and development==
In 1932, the [[Imperial Japanese Navy]] issued a requirement for a new carrier-borne attack aircraft. [[Aichi Kokuki|Aichi]], [[Mitsubishi]] and [[Nakajima Aircraft Company|Nakajima]] responded to this requirement and each built a [[prototype]]. None of these aircraft were deemed satisfactory, and the service thus issued in 1934 a new requirement, 9-''Shi'', for a more capable aircraft to replace the obsolescent [[Yokosuka B3Y]].

[[File:Yokosuka B4Y.jpg|thumb|left]]
The B4Y was designed by [[Sanae Kawasaki]] at the [[Yokosuka Naval Air Technical Arsenal|First Naval Air Technical Arsenal]] at Yokosuka. Regarded only as an interim type, the Navy wanted a [[torpedo bomber]] offering performance comparable to the [[Mitsubishi A5M]] [[monoplane]] [[Fighter aircraft|fighter]]. The result was a biplane with fixed [[landing gear]] and an all-metal structure with metal or fabric skin. To speed development and production, the B4Y utilised the wings from the [[Kawanishi E7K]]. The B4Y1 was also the first Navy carrier attack aircraft to utilize an air-cooled engine, as the prototype that was equipped with the [[Nakajima Hikari]] 2 radial engine performed better than its competitors.<ref>{{Harvnb|Francillon|1979|pp=449–450}}</ref>

The crew of three occupied two [[cockpit]]s. The pilot in the open front cockpit and the other two crewmen, (navigator and radio operator/gunner), in the enclosed rear cockpit.

==Operational service==
[[File:Kaga China Incident.jpg|thumb|right|A Navy Type 96 Carrier Attack Bomber flies near the aircraft carrier [[Japanese aircraft carrier Kaga|''Kaga'']] off China in 1937 or 1938.]]
On 12 December 1937 3 B4Y1s were involved in the [[Panay incident]] during a Japanese attack on the [[United States Navy]] [[gunboat]] ''[[USS Panay (PR-5)|Panay]]'' while she was anchored in the [[Yangtze River]] outside of [[Nanjing]].

Although primarily used as a carrier-based aircraft, the B4Y1 was also used as a land-based [[bomber]] on occasion. In 1940, the [[Nakajima B5N]] replaced the B4Y1 as the primary carrier attack aircraft, though the B4Y1 did remain in service as an advanced [[Trainer (aircraft)|trainer]], and flew from {{Ship|Japanese aircraft carrier|Hōshō||2}} and {{Ship|Japanese aircraft carrier|Unyō||2}} until 1943.

Before its replacement, the B4Y1 had flown during the [[Second Sino-Japanese War]] and served at the [[Battle of Midway]] during June 1942, where eight of them were operated from ''Hōshō''.<ref name="Sword p453">{{Harvnb|Parshall|Tully|2005|p=453.}}</ref> It was one of these planes from ''Hōshō'' which took photographs of the burning {{Ship|Japanese aircraft carrier|Hiryū||2}} on 5 June 1942.<ref name="Sword p356">{{Harvnb|Parshall|Tully|2005|p=356.}}</ref>

==Variants==
;First prototype: {{cvt|559|kW|0}} [[Hiro Type 91 520 hp water-cooled W-12]] driving a two-bladed  propeller.
;Second and third prototypes: {{cvt|477|kW|0}} [[Nakajima Kotobuki 3]] nine-cylinder air-cooled radial driving a two-bladed propeller.
;Fourth and fifth prototype and production aircraft: {{cvt|636|kW|0}} [[Nakajima Hikari 2]] nine-cylinder air-cooled radial driving a two-bladed propeller.

==Production==
* [[Yokosuka Naval Air Technical Arsenal|First Naval Air Technical Arsenal, Yokosuka]]: 5 prototypes (1935–36)
* [[Nakajima Aircraft Company]]: 37 production aircraft (1937–38)
* [[Mitsubishi Heavy Industries]], Nagoya: 135 production aircraft (1937–38)
* [[Hiro Naval Arsenal|11th Naval Air Arsenal]], Hiro: 28 production aircraft (1938)
* Total: 205 aircraft <ref name="Francillon1979p451"/>

==Operators==
;{{JPN}}
* [[Imperial Japanese Navy Air Service]]
The B4Y1 was operated from the aircraft carriers {{Ship|Japanese aircraft carrier|Akagi||2}}, {{Ship|Japanese aircraft carrier |Hōshō||2}}, {{Ship|Japanese aircraft carrier|Kaga||2}}, {{Ship|Japanese aircraft carrier|Ryūjō||2}}, {{Ship|Japanese aircraft carrier|Sōryū||2}}, and ''Unyō'', as well as the 13th and 15th [[Kōkūtai]] (Air Groups).<ref name="Francillon1979p451"/>

==Specifications (B4Y1)==
{{Aircraft specs
|ref=''Japanese Aircraft of the Pacific War'' <ref name="Francillon1979p451">{{Harvnb|Francillon|1979|p=451.}}</ref>
|prime units?=met
<!--
        General characteristics
-->
|crew= 3 (pilot, navigator, radio operator/gunner) 
|length m=10.15
|length note=
|span m=15
|span note=
|height m=4.36
|height note=
|wing area sqm=50
|wing area note=
|aspect ratio=<!-- sailplanes -->
|airfoil=
|empty weight kg=2000
|empty weight note=
|gross weight kg=3600
|gross weight note=
|max takeoff weight kg=
|max takeoff weight note=
|fuel capacity=
|more general=
<!--
        Powerplant
-->
|eng1 number=1
|eng1 name=[[Nakajima Hikari 2]]
|eng1 type=9-cylinder air-cooled radial piston engine
|eng1 kw=<!-- prop engines -->
|eng1 hp=840
|eng1 note=for take-off
::::{{cvt|700|hp|0|order=flip}} at {{cvt|1200|m}}

|prop blade number=2
|prop name=fixed-pitch propeller
|prop dia m=<!-- propeller aircraft -->
|prop dia note=
<!--
        Performance
-->
|max speed kmh=278
|max speed note=
|cruise speed kmh=
|cruise speed note=
|stall speed kmh=
|stall speed note=
|never exceed speed kmh=
|never exceed speed note=
|range km=1573
|range note=
|combat range km=
|combat range note=
|ferry range km=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling m=6000
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ms=
|climb rate note=
|time to altitude={{cvt|3000|m}}
|wing loading kg/m2=72
|wing loading note=
|fuel consumption kg/km=
|power/mass={{cvt|0.1064|hp/lb|order=flip}}
|more performance=
<!--
        Armament
-->
|guns= 1× flexibly mounted, rearward-firing 7.7 mm (0.303 in) [[Type 92 machine gun]] 
|bombs= 1× 800 kg (1,764 lb) torpedo, or 500 kg (1,102 lb) of bombs
}}

==See also==
* [[List of military aircraft of Japan]]

==References==
{{commons category|Yokosuka B4Y}}
;Notes
{{Reflist}}

==Bibliography==
{{refbegin}}
* {{cite book | author=Francillon | title=Japanese aircraft of the Pacific War | publisher=Putnam | publication-place=London | year=1979 | isbn=0-370-30251-6 | oclc=6124909}}
* ''English Translation of Kojinsha No. 6 Warships of the Imperial Japanese Navy.''
* {{cite book |last = Lawrence |first = Joseph |title = The Observer's Book Of Airplanes |location = London and New York |publisher = Frederick Warne & Co |year = 1945}}
* {{cite book | last=Parshall | first=Jonathan | last2=Tully | first2=Anthony | title=Shattered sword : the untold story of the Battle of Midway | publisher=Potomac Books | publication-place=Washington, D.C. | year=2005 | isbn=1-57488-923-0 | oclc=60373935}}
{{refend}}

{{Yokosuka aircraft}}
{{Japanese Navy short aircraft designations}}
{{Allied reporting names}}

[[Category:Yokosuka aircraft|B4Y]]
[[Category:1930s Japanese bomber aircraft|B4Y, Yokosuka]]
[[Category:Single-engined tractor aircraft]]
[[Category:Biplanes]]
[[Category:Carrier-based aircraft]]
[[Category:Aircraft first flown in 1935]]