Nakajima B6N Tenzan (Jill) Carrier-Borne Torpedo Bomber
The promising Nakajima B6N torpedo bomber of WW2 - codenamed Jill by the Allies - arrived at a time when air superiority for the Japanese had slipped away.
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The torpedo bomber was born in the period preceding World War 1 (1914-1918) and had advanced considerably by the time of World War 2 (1939-1945) - though the basic attack concept remained the same. The type was a dedicated platform, its structure designed for the rigors of over-water flight as well as having the strength to carry and deliver a heavy torpedo payload against enemy surface ships. The biplanes of old had given way to all-metal monoplane winged designs by this time though some of the latter were still in service at the outbreak of the Second World War (as was the case with some of the entries concerning the British Royal Navy). The torpedo bomber gave warplanners the capability to launch coordinated attacks from aircraft carriers against enemy ships from the air - broadening torpedo attacks that once relied on warships outfitted with torpedo tubes or submarines lurking for short periods under the water.
The Nakajima Aircraft Company of Japan had been delivering naval-minded aircraft since 1927 (the A1N) and would produce a slew of designs leading up to, and during, the Grand War. In 1937, the prototype that would become the B5N torpedo and dive bomber (codenamed "Kate" by the Allies) flew for the first time. Service entry came a time later and 1,149 examples of this monoplane were produced. With prewar origins, a successor was developed by Nakajima in what became the B6N "Tenzan" ("Heavenly Mountain") and its own first flight was had during March of 1941 but a lengthy development phase meant that service entry was not until August of 1943. Some 1,268 examples of this design followed and the line was codenamed "Jill" by the Allies. The aircraft led a limited operational existence for air superiority had switched to the Allies as the war progressed towards it conclusion in 1945.
The B6N was designed to shore up the limitations discovered operationally with the earlier B5N series - namely performance and range. This led to the Imperial Japanese Navy (IJN) developing a new specification for a carrier-based attack platform of an all-modern design capable of hauling warloads up to 1,800 pounds out to 1,200 miles at cruising speeds of 230 miles per hour. Maximum speed was near the 300 mile-per-hour mark. The new Nakajima "Mamori 11" series 14-cylinder air-cooled radial engine would power the design which would include an operating crew of three made up of a pilot, radioman/gunner and bombardier (doubling as the flight's navigator). Initially it was expected that the Mitsubishi "Kasei" engine would be used - but Nakajima engineers successfully sold authorities on their in-house development instead.
This led to an aircraft of largely conventional design - a long, slender fuselage was required for the performance and hauling capability expected. A single engine, fitted to the nose, would power the airframe. The crew of three would be seated inline under a long-running, heavily-glazed canopy (greenhouse-style) assembly offering exceptional vision around the aircraft. A defensive position was fitted dorsally at the rear of the canopy section with a sole 7.7mm Type 92 machine gun on a trainable mounting being fitted. The torpedo load would be held externally under fuselage centerline. The wing mainplanes were low-mounted and fitted slightly ahead of midships. The tail unit was conventional with its single vertical fin and low-mounted horizontal planes. The undercarriage was of a "tail-dragger" arrangement with the main legs retractable under the wing elements. Dimensions conformed to the hangar elevators of Japanese carriers of the day and Fowler flaps were used to slow the aircraft's attack run and during landing actions on carrier decks. The Nakajima engine powered a four-bladed propeller unit.