Yokosuka B4Y

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B4Y1
Type Torpedo bomber
Manufacturer Yokosuka
Maiden flight 1935
Introduced 1936
Retired 1943
Number built 205

The Yokosuka B4Y1 ("B" for attack , 4th model, "Y" for Yokosuka, "1" for type 1) was a three-seat single engine bi-plane carrier attack airplane employed by the Imperial Japanese Navy Air Service] from 1936 to 1943. The B4Y1 was the last bi-plane carrier-borne attack aircraft used by the Imperial Japanese Navy and replaced the Mitsubishi B2M2. The Allied reporting name was Jean; the Imperial Japanese Navy designation was Navy Type 96 Carrier Attack Plane.

Contents

[edit] Design and development

In 1932 the Imperial Japanese Navy issued a requirement for a new carrier-borne attack aircraft. Aichi, Mitsubishi and Nakajima, responded to this requirement and each built prototype aircraft. However, none of these aircraft were deemed satisfactory, and the service thus issued a 1934 requirement for a more capable aircraft to replace the obsolescent Yokosuka B3Y1. The B4Y1 was designed by Sanae Kawasaki at the First Naval Air Technical Arsenal located in Yokosuka, Japan to meet the new requirements. The B4Y1 was regarded only as an interim type as the Japanese Imperial Navy wanted a torpedo bomber offering greater performance comparable to the Mitsubishi A5M monoplane fighter. The design produced was a bi-plane with fixed landing gear and an all-metal structure covered with either metal or fabric. The wings from the Kawanishi E7K were also used on the B4Y1. The B4Y1 was the first Imperial Japanese Navy carrier attack aircraft to utilize an air cooled engine. The B4Y1 has a crew of three. The pilot sits in an open cockpit while the navigator and the radio operator/gunner are located in an enclosed rear cockpit. Prototype B4Y1 aircraft were manufactured at the First Naval Air Technical Arsenal.

[edit] Operational Service

Although primarily used as a carrier-based aircraft, the B4Y1 was also used as a land-based bomber on occasion. The B4Y1 was operated from the aircraft carriers Akagi, Hōshō, Kaga, Ryūjō, Sōryū, and Unyo; as well as several land based air groups. 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, and flew from the carriers Hōshō and Unyo until 1943. Before its replacement the B4Y1 had flown during the Second Sino-Japanese War and did serve at the Battle of Midway during June 1942, where eight of them were operated from the aircraft carrier Hōshō. It was one of these planes from Hōshō which took photographs of the burning carrier Hiryū on June 5, 1942.

[edit] Variants

  • First Prototype: 750 hp Hiro Type 91 twelve cylinder liquid cooled engine driving a two-bladed propeller.
  • Second and Third Prototypes: Engine 640 hp Nakajima Kotobuki-3 nine-cylinder air-cooled radial driving a two-bladed propeller.
  • Fourth and Fifth Prototype and Production Aircraft: Engine 840 hp Nakajima Hikari-2 nine-cylinder air-cooled radial driving a two-blade propeller.

[edit] Production

  • 205 Total
  • Dai-Ichi Kaigun Koku Gijitsusho, Yokosuka: 5 prototypes (1935-36).
  • Nakajima Hikoki K. K.: 37 production aircraft (1937-38).
  • Mitsubishi Jukogyo K. K., Nagoya: 135 production aircraft (1937-38).
  • Dai-Juichi Kaigun Kokusho, Hiro: 28 production aircraft (1938).

[edit] Operators

Flag of Japan Japan

[edit] Specifications

General characteristics

  • Crew: 3 (pilot, navigator, radio operator/gunner)
  • Length: 10.15 m (33.3 ft)
  • Wingspan: 15.0 m (14.2 ft)
  • Height: 4.36 m (14.3 ft)
  • Wing area: 50 m² (548 ft²)
  • Empty weight: 2,000 kg (4,400 lb)
  • Max takeoff weight: 3,600 kg (7,900 lb)
  • Powerplant:Nakajima Hikari-2 9-cylinder radial engine, 626 kW (840 hp)

Performance

Armament 1 x 7.7 mm (0.303 in) flexible rear-firing Type 92 machine gun 1x800 kg torpedo, or 500 kg of bombs.

[edit] References

  • Francillon, R. Japanese Aircraft of the Pacific War. Naval Institute Press, 1987.
  • English Translation of Kojinsha No. 6 Warships of the Imperial Japanese Navy.

Related lists List of military aircraft of Japan