Ki-51 / Type99 Assault Plane

Hasegawa Ki-55

The ”Mitsubishi Ki-51 / Type 99 Assault Plane  (Allied Designation: “Sonia”) was a light bomber /dive bomber / attacker and tactical reconnaissance plane  in service with the Imperial Japanese Army before and during World War II. It was primarily used in China and Southeast Asia where enemy fighter resistance was limited. It was well-regarded as a rugged and versatile aircraft capable of taking off from rough or unpaved runways with a number of bomb configurations up to 300 kg. It had two forward-firing machine guns in its wings and a flexible machine gun manned by a rear-facing gunner.

Why? The Ki-51 is a versatile land-based attacker and recon plane similar to the carrier-based Aichi D3A1, but with some better performance characteristics such as a much lower empty weight and better top speed.

In game scenarios: The Ki-51 could be used in a unique tactical recon mission, utilizing the side and bottom square window ports for taking camera images of enemy locations (you will find the small camera part and clear windows in model kits such as in the Hasegawa 1/72 model), then being equipped to bomb whatever important targets it discovers. With a decent forward and rear armament, the tactical recon plane was capable of fending off the hodge-podge of older foreign-sourced planes from the Chinese air force, for example, and the player could make a desperate battle to fend off such forces while attempting to return safely to base with intelligence images. Games that are based in historical maps deep in inland in China or Southeast Asia should use the Ki-51 (or Ki-30) instead of the D3A1 or other carrier-based planes.


Despite dating back to 1939, the Ki-51 proved its versatility on land and even at sea during WW2. In 1945, two depth charge-equipped Ki-51 planes performing sub-hunting duties over water were credited with the last successful sinking of a U.S. submarine by Japan.

A Ki-71 prototype with a more powerful engine, two 20mm cannons, and retractable landing gear could utilize the same basic in-game model design, offering a potential upgraded model, saving game developers time.


  • Crew: Two
  • Length: 9.21 m (30 ft 2⅝ in)
  • Wingspan: 12.1 m (39 ft 8⅜ in)
  • Height: 2.73 m (8 ft 11½ in)
  • Wing area: 24.0 m² (259 ft²)
  • Empty weight: 1,873 kg (4,129 lb)
  • Loaded weight: 2,798 kg (6,169 lb)
  • Max. takeoff weight: 2,920 kg (6,415 lb)
  • Powerplant: 1 × Mitsubishi Ha-26 II 14 cylinder air cooled radial engine, 709 kW (950 hp)


  • Maximum speed: 424 km/h at 3 000 m (229 kn, 263 mph at 9,840 ft)
  • Range: 1,060 km (574 nmi, 660 mi)
  • Service ceiling: 8,270 m (27,130 ft)
  • Wing loading: 117 kg/m² (23.8 lb/ft²)
  • Power/mass: 0.24 kW/kg (0.15 hp/lb)
  • Climb to 5,000 m (16,400 ft): 9 min 55 sec


  • Guns:
  • Bombs: 200-300 kg (441 – 661 lb) bombs (normal operations); 250 kg (551 lb) for suicide operations[2]

The Ki-51:

In February 1938 the Mitsubishi Corporation of Japan received an order for a new aircraft to attack enemy ground units. It was designed to be faster and more maneuverable than existing bomber aircraft. Great emphasis was placed on maneuverability, protection for the crew and the capability of operating from emergency airfields located near combat areas. Specifications called for a maximum speed of no less than 260 mph (420 km/h) at 6,578 ft (2000 m), take-off weight was to be 5,960 lbs (2700 kg) and it was to have a bomb load of at least 440 lbs (200 kg) and defensive armament consisting of three machine guns, one which was on a moveable rear-facing mount. In December of 1938 Mitsubishi modified the plane for additional use for recon missions as an armed Tactical Recon plane. It was completed in June 1939 as the Type 99 Attacker / Tactical Reconnaissance Plane. It first flew in mid-1939

Initially deployed against Chinese ground forces, the Ki-51 light bomber later proved to be too slow for utilization in the Pacific where newer fighter aircraft of the Allied powers could outfly and outgun it. In this way it was similar to the German Stuka bombers that while once very effective in stand alone operations later required fighter escorts for protection.  The Ki-51 was still useful in areas of Asia where it was not threatened in the sky by newer fighters and performed a useful ground-attack role in the China Burma India Theater, notably from airfields too rough for many other aircraft. As the war drew to a close, they began to be used in so-called ”kamikaze” attacks. Total production was around 2,385 units.

On the day of the Atomic bombings of Hiroshima and Nagasaki, two Ki-51s scored the last Japanese victory against US submarines, and of which is confirmed as the 52nd USN submarine lost during the war. Two depth charges hit the USS Bullhead, SS-332, which sank with all hands.

The Ki-71 was an attempt made in 1941 to develop an advanced version of the Ki-51 by the Manshū Aircraft Company in Japan occupied Manchuria (Manchukuo). This experimental design featured a more powerful engine, two 20mm cannons, and retractable landing gear (in place of the Ki-51’s fixed gear). Despite the enhancements, however, maximum speed was only 292 mph, and the design was not accepted for production. Only three examples were built, but the project was known to the Allies and the design was given the codename “Edna”.

Ki-51 with tactical windows behind and beneath cockpit

Ki-51 with tactical recon window slots behind and beneath cockpit


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