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Nakajima B5N

Nakajima · Torpedo Bomber · Japan · Interwar (1919–1938)

The Nakajima B5N (Allied reporting name Kate) was an Imperial Japanese Navy three-seat torpedo bomber — the principal IJN torpedo bomber of WWII through 1943 + the aircraft that delivered most of the torpedo strikes that sank Pearl Harbor's battleships on 7 December 1941. Katsuji Nakamura designed the B5N at Nakajima in 1935-1937; the prototype first flew in January 1937. About 1,150 B5Ns were built between 1937 and 1942 at Nakajima Ota + Aichi + Hiro Naval Arsenal. The aircraft served IJN carrier + land-based torpedo squadrons 1937-1944.

The B5N2 (most-numerous variant) used a Nakajima Sakae 11 14-cylinder radial engine (1,000 hp). Maximum speed 378 km/h, range 1,990 km, service ceiling 8,260 m. Armament: 1 × Type 91 800 kg torpedo or 800 kg of bombs + 1 × 7.7 mm rear machine gun. Crew: 3 (pilot + observer/bombardier + radio operator/gunner). The aircraft's range + payload were notably better than contemporary Allied torpedo bombers (Devastator, Swordfish) at WWII outbreak — Pearl Harbor B5Ns flew 360 km from carriers + delivered devastating torpedo attacks that sank battleships USS Arizona + Oklahoma + others.

B5N service was central to early-war IJN successes. Pearl Harbor (December 1941) — 40 B5Ns delivered torpedo strikes sinking 5 battleships. Coral Sea + Midway + Eastern Solomons + Santa Cruz battles 1942 — B5Ns engaged USN carriers + sank USS Lexington, Yorktown, Hornet. By 1943 the type was outclassed by USN Hellcat fighters + replaced by the Nakajima B6N Tenzan. Surviving B5Ns served as ASW patrol + training aircraft 1944-1945. About 0 B5N airframes survive complete.

For Kids — a shorter, friendlier version

The Nakajima B5N Kate was Japan's main torpedo bomber at the start of World War II. The B5N first flew in 1937 and entered service in 1939. It became famous for attacking Pearl Harbor on December 7, 1941 — about 40 B5N torpedo bombers helped sink American battleships in Pearl Harbor.

The B5N is about 34 feet long — slightly bigger than a school bus. One Nakajima Sakae radial engine. Top speed only 235 mph — slow even by 1939 standards. Three crew members: pilot, observer/bombardier, gunner. The B5N carried one large torpedo or 1,800 pounds of bombs.

Allied pilots called the B5N "Kate." It fought in many battles besides Pearl Harbor: the Battle of Midway, the Coral Sea, and the Philippines. B5Ns sank American aircraft carriers Lexington (at Coral Sea, May 1942) and Hornet (at Santa Cruz, October 1942) plus many other ships.

About 1,150 B5Ns were built between 1937 and 1942. By 1943, Japan replaced the B5N with the faster B6N. After WWII, very few B5Ns survived because Japan had to destroy its airplanes under the Allied occupation. Only 1 nearly-complete B5N exists today — recovered from a sunken Japanese carrier at the bottom of the Pacific Ocean.

Fun Facts

Allied pilots called the B5N "Kate."
About 40 B5N torpedo bombers attacked Pearl Harbor on December 7, 1941.
B5Ns sank American aircraft carriers Lexington (May 1942) and Hornet (October 1942).
About 1,150 B5Ns were built between 1937 and 1942.
Three crew members: pilot, observer/bombardier, gunner.
The B5N carried one large torpedo or 1,800 pounds of bombs.
Only 1 nearly-complete B5N survives today — recovered from a sunken Japanese carrier.

Kids’ Questions

How does a torpedo bomber work?

A torpedo bomber flies low (about 50-100 feet above the water) and slow (about 130 mph) toward an enemy ship. At just the right moment, the pilot releases a heavy torpedo that drops into the water. The torpedo's own engine then propels it underwater toward the enemy ship. When the torpedo hits the ship's hull, it explodes — usually below the waterline, where the damage is worst. Torpedo bombers were dangerous to fly (slow + low + close to the target = easy to shoot down). But in WWII, before radar-guided missiles, torpedo bombers were the most effective way to sink large warships from the air.

Why use girls' names for Japanese airplanes?

During WWII, the Allied military created a naming system for Japanese aircraft to avoid confusion. Japanese names (like "Nakajima B5N" or "Mitsubishi A6M") were complicated to memorize and pronounce. So Allied intelligence assigned simple American-style nicknames. Female names were used for bombers and transports (Betty, Kate, Mavis, Sally). Male names were used for fighters (Zeke for Zero, Oscar for Ki-43, Tony for Ki-61, Frank for Ki-84). The names made radio communication easier — "there are six Bettys at 10,000 feet" was clearer than the Japanese designation. The system worked well throughout the Pacific war.

Variants

B5N1 (early): Initial production. About 200 built.
B5N2 (refined): Improved Sakae-11-engined variant. About 950 built.

Notable Operators

Imperial Japanese Navy (1937-1944): Principal user. Carrier + land-based torpedo squadrons across Pacific theatre.

Frequently Asked Questions

Did B5Ns attack Pearl Harbor?

Yes — 40 B5Ns delivered torpedo strikes during the 7 December 1941 Pearl Harbor attack. They sank USS Arizona (with bombs hits, not torpedoes for that ship) + USS Oklahoma + USS West Virginia + USS California + damaged USS Nevada. The B5N's torpedo attacks were responsible for most of the day's battleship damage; the bomb attacks (B5Ns also carried 800 kg bombs in some configurations) caused additional destruction. The Pearl Harbor attack remains the most-large single B5N combat operation.

How many B5Ns were built?

About 1,150 airframes 1937-1942 across Nakajima Ota + Aichi + Hiro Naval Arsenal. Production ended 1942 when the more-capable Nakajima B6N Tenzan entered IJN service. By 1943 most B5Ns had been transferred to ASW patrol + training roles.

Sources

Wikipedia — Nakajima B5N