See Restored WWII Japanese Fighter Featuring Liquid Cooling Technology

A Different Fighter Design

The Kawasaki Ki-61 Hien was a Japanese fighter plane used during World War II. Unlike most Japanese aircraft of that time, which were lightweight and used radial engines, the Ki-61 used a liquid-cooled inline V12 engine. This engine was based on a German design, the Daimler-Benz DB 601, and gave the aircraft a sleek and narrow shape.

Built by the Kawasaki Aircraft Company, the Ki-61 first flew in late 1941. Its design caused confusion among Allied pilots when it appeared in combat. Because of its European look, some believed it was a German or Italian plane. This led to its Allied code name—Tony.

Performance in Combat

The Ki-61 stood out in battle. It had better armor protection and self-sealing fuel tanks, which made it more durable than other Japanese fighters like the Zero. It could fight faster planes such as the P-38 Lightning, P-40 Warhawk, and even the P-51 Mustang. The Ki-61 also had strong diving ability and good speed for its time.

Its versatility allowed it to be used in many roles. It served as a bomber escort, interceptor, and near the end of the war, even in suicide missions. Early versions had four machine guns, while later models carried 20 mm cannons, making them better suited to attack heavy bombers.

Notable Units and Engine Problems

Pilots of the 244th Sentai, including Major Teruhiko Kobayashi, used the Ki-61 to defend Japan during American bombing raids. Kobayashi became known for his bravery in facing large groups of bombers.

Despite its strengths, the Ki-61 had problems. Its engine often broke down in hot climates, and spare parts were hard to find. Some versions were later changed to use radial engines, creating a new type called the Ki-100.

Role in Late-War Defenses

Toward the end of the war, the Ki-61 was one of the few planes able to reach the high altitude of American B-29 bombers. While not ideal for such missions, it was used anyway. These late missions were often dangerous and showed how critical Japan’s situation had become.

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