Mitsubishi Ki-51 Type 99 “Sonia”

In December 1937 the Japanese Army requested that Mitsubishi work on a development of their Ki-30 light bomber, with an emphasis on creating a new light bomber that could operate from advanced airfields very close to the fighting front. The idea was to create an aircraft that could co-operate very closely with ground troops during combat operations. The result was the Ki-51 Type 99 Assault Plane.

The Ki-51 bore a strong resemblance to the parent Ki-30 design from which it was derived. The cockpit was rearranged to allow closer co-operation between the two crew members, and the bomb bay was deleted with a lighter bomb load carried externally. This change also allowed the wing to be redesigned and the landing gear shortened, although the fixed undercarriage was retained.

Ki-51s were assigned to China-based units during 1940, and the aircraft proved useful in its intended role. It was, however, exceedingly vulnerable to enemy fighters and so was only useful in areas where the Japanese enjoyed complete control of the air. In the initial stages of the Pacific War air supremacy allowed the Ki-51 to operate successfully over Malaya, Java and Burma.

Later in the war as the Allies began to regain control of the air the Ki-51 began to suffer as a consequence. Soon it was withdrawn from front line roles and relegated to rear areas, where like most obsolete Japanese aircraft it was assigned to the kamikaze role.

In 1942 the Ki-51 was assigned the Allied reporting name “Sonia”. An updated version, the Ki-71, was never put into production but nevertheless assigned its own reporting name, “Edna”.