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Ki-51 “Sonia”, Japanese Light Bomber


Photograph of Ki-51 "Sonia"

Wikipedia Commons

3-view diagram of Ki-51 "Sonia"

U.S. Army. Via ibiblio.org


Mitsubishi Ki-51 "Sonia"


Specifications:


Crew

2 in tandem cockpit

Dimensions

39'8" by 30'3" by 8'11"
12.09m by 9.22m by 2.72m
Wing area 259 square feet
24 square meters

Weight

4129-6415 lbs
18873-2910 kg

Maximum speed      

263 mph at 9845 feet
423 km/h at 3000 meters

Climb rate

28 feet per second
8.5 meters per second

Ceiling

27,130 feet
8270 meters

Power plant

One 940 hp (700 kW) Type 99 Model 2 (Mitsubishi Ha-26-II) 14-cylinder radial engine driving a variable-pitch 3-bladed metal propeller

Armament

2 12.7mm Type 1 machine guns (wings)
7.7mm Type 89 machine gun (rear cockpit)

External stores     

441 lbs (200 kg) of bombs normal
551 lbs (250 kg) of bombs as kamikaze

Range

660 miles
1060 km

Production

A total of 2385 aircraft as follows:
  Mitsubishi Jukogyo K.K. (Nagoya):

 

12 prototypes and service trial aircraft by December 1939
1459 production aircraft from January 1940 to March 1944


Tachikawa Dai-Ichi Rikugun Kokusho:


913 production aircraft from July 1941 to July 1945


"Sonia" was a more successful design than "Helen", serving throughout the Pacific. Though somewhat slow, it was unusually well protected for a Japanese design, was easily maintained, and was well-liked by its crews. It had a good rough-field capability.

The design originated in December 1937 with a specification issued to Mitsubishi for a ground attack aircraft based on the Ki-30 "Ann". The Japanese Army wanted a smaller aircraft capable of operating on short airstrips close to the front. The design team shortened the cockpit and gave the rear cockpit a limited set of instruments and controls. The bomb bay was eliminated and the wings were lowered to permit a sturdier undercarriage. A prototype was completed in June 1939 and, with modifications to improve handling and the addition of 6 mm armor plating around the cockpit and engine, the design went into production in January 1940.

The aircraft was designed so that the rear cockpit instruments and controls could be replaced with camera equipment for photoreconnaissance.

"Sonia" was so well liked by its crews that a new production line was set up as late as 1944 at Tachikawa First Air Arsenal (Tachikawa Dai-Ichi Rikugun Kokusho). The aircraft was assigned to kamikaze missions in the final months of the war, and a few relic aircraft were used by the Indonesian Air Force against Dutch forces postwar. An attempt to produce a more powerful version with retractable landing gear in Manchuria came to naught, but was discovered by Allied intelligence, who assigned the new aircraft the code name "Edna".

References

Francillon (1979)


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