# Mitsubishi Ki-51

The Mitsubishi Ki-51 (Army designation "Type 99 Assault Plane"; Allied reporting name Sonia) was a light bomber/dive bomber in service with the Imperial Japanese Army during World War II. It first flew in mid-1939. Initially deployed against Chinese forces, it proved to be too slow to hold up against the fighter aircraft of the other Allied powers. However, it 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, the Japanese began using them in kamikaze attacks. Total production was around 2,385.
On the day Hiroshima was destroyed by an atomic bomb, a Ki-51 was responsible for the last Japanese sinking of a US warship, sinking the submarine USS Bullhead with all hands.

## Variants

* Prototypes: two built
* Service trials: 11 built
* Ki-51: 2,372 built (Manufacturers: Mitsubishi (1,462), Tachikawa Army Air Arsenal (913)) until March 1944
* Ki-51A: reconnaissance version.
* Ki-51B: assault version with armor and bomb racks to carry 200 kg (441 lb) of bombs. It could also be fitted with an aerial camera.
* Mansyu Ki-71: three prototypes built by Mansyu with retractable landing gear, did not enter production.

## Operators
### Japan

* Imperial Japanese Army Air Force

### China

* Communist Chinese (captured): The last 4 of around 100 Ki-51s were retired in 1953.

### France

* French Air Force - At least two Ki-51 was used by French Air Force in Indochina during First Indochina War.

### Indonesia

* Indonesian Air Force - In late 1945, the Indonesian People's Security Army (TKR) captured some aircraft at former Japanese bases, including Bugis Air Base in Malang. Most aircraft were destroyed during the Indonesian National Revolution of 1945–1949. Two Yokosuka K5Y "Cureng" and a Ki-51 "Guntei" carried out a bombing operation against the Dutch on 29 July 1947.

### Democratic People's Republic of Korea

* Following independence, transferred from the Soviet Union.

### Republic of Korea

* Used by South Korean Airforce during Korean War

## Surviving aircraft

The only complete survivor of Ki-51 is part of the collection of the Dirgantara Mandala Museum in Indonesia. The aircraft was found abandoned at the Babo Airfield in West Papua province. The aircraft was likely stripped for spare parts and later abandoned. Before the aircraft was recovered, its propeller blade was cut off, with its engine cowling and cockpit canopy was missing. The aircraft was recovered from Babo airfield in 1987, was restored and then displayed with Indonesian Air Force markings at the Dirgantara Mandala Museum.

## Specifications (Ki-51)

Data from Japanese Aircraft of the Pacific War
General characteristics
* Crew: 2
* Length: 9.21 m (30 ft 3 in)
* Wingspan: 12.1 m (39 ft 8 in)
* Height: 2.73 m (8 ft 11 in)
* Wing area: 24 m$^2$ (260 sq ft)
* Empty weight: 1,873 kg (4,129 lb)
* Gross weight: 2,798 kg (6,169 lb)
* Max takeoff weight: 2,920 kg (6,437 lb)
* Powerplant: 1 × Mitsubishi Ha-26-II 14-cylinder air-cooled radial piston engine, 710 kW (950 hp)
* Propellers: 3-bladed variable-pitch propeller
Performance
* Maximum speed: 424 km/h (263 mph, 229 kn) at 3,000 m (9,800 ft)
* Range: 1,060 km (660 mi, 570 nmi)
* Service ceiling: 8,270 m (27,130 ft)
* Time to altitude: 5,000 m (16,000 ft) in 9 minutes 55 seconds
* Wing loading: 117 kg/m$^2$ (24 lb/sq ft)
* Power/mass: 0.24 kW/kg (0.15 hp/lb)
Armament
* Guns:
** 2 × fixed, forward-firing 7.7 mm (.303 in) Type 89 machine guns (replaced with 2 × 12.7 mm (.5 in) Ho-103 machine guns in later models)
** 1 × 7.7 mm (.303 in) Te-4 Machine gun rearward-firing machine gun.
* Bombs: 200 kg (440 lb) bombs (normal operations); 250 kg (550 lb) for suicide operations