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Japan's Imperial Army flag

Japan's Mitsubishi Ki-51 ground attack; Army Type 99
Allied code name: Sonia

Photos

  • Mitsubishi Ki-51 Sonia ground attack

Design

The Mitsubishi Ki-51 met a 1937 requirement for an aircraft that could take off from short strips near the front lines. The Ki-51 was designed by Kawano, Ohki, and Mizuno.

Requirements:

  • Speed: 260 mph at 6,500', 261 mph at 6,560', 420 kph at 2,000 m
  • Weight: 5,952 lb, ~6,000 lb, 2,700 kg
  • Bombs: 440 lbs , twelve 33 lb / 15 kg or four 110 lb / 50 kg
  • Armament: three machine guns, two MG in wings, one MG in rear cockpit
  • Engine: Mitsubishi Ha-26-II radial

The Ki-51 was of all metal construction.

Wings

The wings were mounted low in the fuselage.

Main Armament

The early production aircraft had 7.7 mm MG in the wings and these were later replaced by 12.7 mm MGs. At the same time additional fuel tanks were added to the wing leading edges.

Landing Gear

The landing gear on the Ki-51 were fixed.

Cockpit

The pilot and navigator/bombardier were located in an all glass cockpit. The were placed close together to allow for better communication.

Field Modifications

In the field the Ki-51 could be modified for either ground attack or reconnaissance.

Prototype

In June and August 1939 the two prototypes were first flown.

Production

Mitsubishi produced Ki-51s until March 1944 and Tachikawa until July 1945.

  • Prototypes: 2
    • Production: June - August 1939
  • Service trials: 11
    • Production: September - December 1939
  • Mitsubishi Ki-51: 2,372
    • Manufacturers: Mitsubishi (1,459, 1,462), Tachikawa Army Air Arsenal (913)
    • Production: June 1940 - March 1944 (Mitsubishi), July 1941 - July 1945 (Tachikawa)
  • Total: 2,385
    • Manufacturer: Mitsubishi Jukogyo K.K. at Nagoya, Tachikawa Dai-Ichi Rikugun Kokusho (Tachikawa Army Air Force Arsenal) at Tachikawa
    • Production: 1940 - July 1945
  • Mitsubishi Ki-71 Prototypes: 3
    • Manufacturer: Tachikawa Army Air Arsenal

Variants

  • Mitsubishi Ki-51:
  • Mitsubishi Ki-51a, Army Type 99 Tactical Reconnaissance: Service trial aircraft with cameras for reconnaissance.
  • Mitsubishi Ki-71, "Edna": Prototype. Reconnaissance. Undercarriage was retractable. Had a Mitsubishi Ha-112-II engine (1,500 HP). Was to have two 20 mm Ho-5 cannons in the wings.

Usage

Even though the Ki-51 never excelled in its classification it was well liked for its ability to withstand punishment, reliability, and manauverability.

Units

  • Sentais: 6th, 27th, 32nd, 44th, 65th, 66th, 67th, 83rd
  • Kokuritsu Hiko Chutais: 41st, 45th, 47th, 48th, 49th, 52nd, 53rd, 71st, 73rd, 83rd, 89th, 90th, 91st
  • 4th Kokugun Shireibu Hikodan
  • Koku Shikan Gakko (Army Air Academy)

Sino-Japanese War

The Ki-51 was first used in China.

Suicide

Towards the end, the Ki-51 was used as a suicide plane.

Dutch Post World War II

The Dutch confiscated some abandoned Ki-51s and used them in the Indonesian Air Force.

Specifications

  Mitsubishi Ki-51
Type Attack, Ground attack, Reconnaissance
Crew 2
Engine (Type) Mitsubishi Ha-26-II
Cylinders Radial, Radial 14
Cooling Air
Net HP 940, 950
Propeller blades 3, 3 metal variable pitch
Dimensions  
Span 39' 8", 39' 8.375", 39' 8.4", 39' 8.5"
12.1 m
Length 30' 2", 30' 2.2", 30' 2.5", 30' 2.59"
9.2 m, 9.21 m
Height 8' 11", 8' 11.5"
2.73 m
Wing area 258.548 sq ft, 258.56 sq ft
24.02 sq m
Weight  
Empty 4,129 lb
1,873 kg
Loaded 6,169 lb
2,798 kg
Maximum loaded 6,415 lb, 6,437 lb
2,910 kg, 2,920 kg
Performance  
Speed at 9,845' / 3,000 m 263 mph, 264 mph
423 kph, 424 kph, 425 kph
Climb to 16,405' / 5,000 m 9.9 minutes, 9 minutes 55 seconds
Service ceiling 27,130'
8,270 m
Range 659 miles, 660 miles
1,060 km, 1,062 km
Armament 3: MG
Wings - early aircraft 2: 7.7 mm Type 89 MG
Wings - later aircraft 2: 12.7 mm Type 1 MG
Rear cockpit 1: 7.7 mm Type 89 MG
Bombs 440 lb, 441 lb
200 kg
Bombs - suicide mission 551 lb
250 kg

Sources:

  1. Aircraft of WWII, Stewart Wilson, 1998
  2. World War II Airplanes Volume 2, Enzo Angelucci, Paolo Matricardi, 1976
  3. The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
  4. Japanese Aircraft of the Pacific War, René J Francillon, 1970
20th Century American Military History Crucial Site