The Mitsubishi B2M naval attack aircraft was procured as a replacement for the wooden Mitsubishi B1M. Intended for Japanese production, the Imperial Japanese Navy sought to ensure its success by seeking tenders for prototypes from British manufacturers.
Blackburn’s design, the T.7B (Japanese designation 3MR4) was a large, three seat all-metal two-bay biplane, powered by a single 625 hp Mitsubishi-Hispano-Suiza Type 51-12Lbr engine.
The single British-built prototype was completed for final inspection on 29th November 1929 and was flown for the first time on 28th December and it was shipped to Japan, arriving in February 1930.
The three crew (for reconnaissance operations) sat in separate cockpits and comprised pilot, wireless operator / bomb-aimer and observer / gunner.
For torpedo operations, this was reduced to two crew, with the fuel load being limited to 100 gallons.
In addition to the torpedo, armament consisted of a fixed forward-firing Vickers gun on the port side and twin Lewis guns fired from the rear cockpit. An optional fourth gun could be carried, fired through an opening in the floor of the centre cockpit. With full fuel (and no torpedo), two 250 lb bombs could be carried between the undercarriage legs.
Blackburn’s Chief Engineer travelled to Japan to oversee the manufacture and development of the initial production aircraft.
A number of minor issues had to be resolved before the third locally-built version was adjudged to have met the Navy’s requirements. The type was then adopted as the Navy Type 89-1 although it was also known as the Mitsubishi B2M1 when fitted with a 650 hp Mitsubishi-Hispano Type 7 engine.
The Japanese-built aircraft adopted a rounded fin and rudder shape and a retractable coolant radiator.
The Blackburn-built prototype was lost in an accident when it was inadvertently flown without the main engine oil cock having been selected ‘on’.
As initially built, the type suffered from poor serviceability and a series of modifications in 1934 resulted in the B2M2 which was used extensively for bombing attacks against China at the start of the second Sino-Japanese War in 1937.
A total of 205 B2M1 / B2M2 were built in Japan and the B2M2 variant was armed with two guns and could carry an increased bomb load over short ranges. It also featured a triangular fin and rudder, reduced wingspan and revised nose lines.
The type served on Japanese carriers from 1933 until 1937 and was also used in the training role.
Variants & Numbers Built
|Prototypes||One only Blackburn T.7B|
|Production||205 aircraft as B2M1 and B2M2|
|Blackburn T.7B (Recce)||Mitsubishi B2M1||Mitsubishi B2M2|
|Powerplant||One 625 hp Hispano-Suiza Type 51-12L.br engine||One 650 hp Mitsubishi-Hispano Type 7 engine|
|Span||49 ft 3.5 in||49 ft 11 in||49 ft 1 in|
|Maximum Weight||7,500 lb||7,936 lb|
|Capacity & Armament||Three crew; one forward-firing Vickers gun, two rear Lewis guns in rear cockpit, optional gun below centre cockpit; 2 X 250 lb bombs.||Three crew, one fixed Vickers plus one Lewis gun and up to 1,764 lb bomb load|
|Maximum Speed||135 mph at sea level||132 mph at sea level||140 mph at sea level|
|Cruise speed||115 mph||112 mph||119 mph|
|Range||800 miles||1,100 miles||1,090 miles|
No Blackburn T.7B, or Mitsubishi B2M1 or B2M2 aircraft survive.