For reconnaissance duties the crew consisted of pilot, wireless
operator/bomb-aimer and observer/gunner sitting in three separate
cockpits and placed close together for ease of intercommunication,
either verbally or by hand-written notes. An aperture in the floor
of the centre cockpit served the dual-purpose of course-setting
bomb-sight mounting and optional fourth gun position, the Lewis
being carried on rails in the floor and stowed under it when not in
use. For torpedo-carrying the crew was reduced to two and the fuel
to 454 litres (100 Imp gal).
The prototype Blackburn T.7B, or 3MR4, was completed at the end
of November 1929 and first flown at Brough without markings by A M
Blake on 28 December 1929 that year. Test flights were made with
and without torpedo but no time was lost, for records show that it
was packed form shipment to Japan on 3 January 1930, arriving there
the following month. Accompanying the aircraft was its chief
British designer, G E Petty and a Blackburn working party, who were
to assemble the aircraft on arrival and to supervise the building
of additional aircraft.
On arrival it was painted up with the Japanese Rising Sun disc
insignia and closely examined by Mitsubishi engineers who
immediately began tooling-up the factory and making ready for
production. There examination was, if anything too searching, for
the handle of the starting magneto was placed in the cockpit in
such a position that it could not rotate (and therefore the engine
could not start), unless the main oil cock was turned on; failing
to see the wisdom of this arrangement, the Japanese repositioned
the handle without reference to the designer, with the inevitable
result that one of their pilots took-off without turning on the
main oil supply and the aircraft crashed upside down in a paddy
field when the engine seized. A second prototype, completed on 31
October, 1930, was powered by a 650 hp Mitsubishi Type Hi engine,
but was lost due to a pilot error. The third prototype, completed
on 2 February, 1931, was delivered to the Navy but suffered from
shortcomings, such as engine oil overheating, difficulty in making
a three-point landing which is so essential for carrier operations,
and poor stability. The fourth prototype, with modifications to
overcome the failings of its predecessors, performed well and was
officially accepted as the Navy Type 89-1 Model 1 Carrier Attack
Aircraft (short designation B2M1) in March 1932 and put into
production. Unlike those of Blackburn's prototype, the fin and
rudder were a rounded shape and the elevator horn balances were
reduced in size. The nose was made slimmer by deleting the
shuttered chin compartment and fitting a retractable radiator, and
the tailplanes of late production machines had rounded ends and
unbalanced elevators.
As the new aircraft entered service, engine problems and other
shortcomings were discovered and frequently encountered during this
transitional period. In addition, it was said to have had poor
performance and poor operating cost. To correct these deficiencies,
engineers Ohgi and Masufuji made changes in the materials used and
manufacturing technique. As a result, this aircraft became the Navy
Type 89-2 Carrier Attack Aircraft (B2M2), which remained in
production until 1935. This variant of the Type 89 was armed with
two instead of four machine-guns and able to carry 800 kg (1,764
lb) of bombs over short distances. This aircraft also featured
wings of reduced span, a triangular fin and rudder and an even
slimmer nose. Even allowing for 50 per cent greater tankage, both
variants came out much overweight compared with the Blackburn
T.7B.
In spite of high expectations for the new aircraft as a
replacement for the Mitsubishi Type 13 Carrier Attack Aircraft, the
Type 89 had a bad reputation with operational units even after the
improvements which resulted in the Type 89-2. However, with the
structure of steel and aluminium, the excellent characteristics of
the Blackburn B-9 aerofoil, and use of Handley Page slots were
valuable for future designs.
Although total production of the B2M1 and B2M2 amounted to 205
aircraft, it is said not to have been a worthwhile undertaking by
Mitsubishi, who found the new constructional techniques very
costly, compared with the machine's wooden predecessor, and the
manufacturing licence for the Handley Page slots expensive. In
addition, the unreliability of Japanese-built engines is believed
to have led to a number of fatal accidents. Both variants served
aboard the carriers Ryujo, Akagi and Kaga from 1933 until the
Sino-Japanese war of 1937. Small numbers of Type 89 Attack Aircraft
participated in campaigns during the Shanghai Incident, as did
earlier Type 13 Carrier Attack Aircraft. Others were operational on
the Japanese mainland with the Tateyama Air Corps and as carrier
trainers with Omura Air Corps. Some of the Type 89s were donated to
the Navy through the Hokoku-go programme, and, later the Type 89
design was released by the Navy as a civilian conversion, the
Mitsubishi Type 89 General Purpose Aircraft.
Technical Data
Manufacturer: (1st prototype) Blackburn Aeroplane and Motor Car
Co Ltd,
Mitsubishi Kokuki KK (Mitsubishi Aircraft Co Ltd).
Type: Single-engined carrier-borne attack aircraft.
Crew (2-3): (Reconnaissance) Pilot, wireless operator/bomb-aimer
and observer/gunner or (torpedo-bomber) pilot and observer/gunner
in tandem open cockpits.
Powerplant: One 650 hp Mitsubishi-built Type Hi (Hispano Suiza)
twelve-cylinder vee water-cooled engine, driving a two-blade wooden
propeller.
Armament: One (B2M1) fixed forward-firing 7.7 mm (0.303 in)
Vickers machine-gun fitted along the port side of the fuselage, one
flexible twin-mounted 7.7 mm (0,303 in) Lewis machine-guns on a
double rotating mounting over the observer's cockpit, and optional
7.7 mm (0.303 in) Lewis machine-gun firing from ventral aperture in
the floor of the central cockpit, (B2M2) one fixed forward-firing
7.7 mm (0.303 in) machine-gun and one flexible mounted 7.7 mm
(0.303 in) machine-gun in observer's cockpit. Bomb load: One 907 kg
(2,000 lb) Type 90 or Type 94 torpedo or two 113 kg (250 lb) bombs,
or (B2M2) one 800 kg (1,764 lb) bomb.
Dimensions: Span (B2M1) 15.22 m (49 ft 11 1/4 in), (B2M2) 14.98
m (49 ft 1 3/4 in); length (B2M1) 10.27 m (33 ft 8 1/2 in), (B2M2)
10.18 m (33 ft 4 3/4 in); height (B2M1) 3.712 m (12 ft 2 in),
(B2M2) 3.60 m (11 ft 9 1/2 in); wing area (B2M1) 55 sq m (592.034
sq ft), (B2M2) 49 sq m (527.448 sq ft).
Weights: Empty (B2M1) 2,260 kg (4,982 lb), (B2M2) 2,180 kg
(4,806 lb); loaded 3,600 kg (7,936 lb); wing loading (B2M1) 65.5
kg/sq m (13.34 lb/sq ft), (B2M2) 73.5 kg/sq m (15 lb/sq ft); power
loading (B2M1)4.87 kg/hp (10.7 lb/hp), (B2M2) 4.55 kg/hp (10
lb/hp).
Performance: Maximum speed (B2M1) 115 kt (132 mph), (B2M2) 123
kt (142 mph); climb to 3,000 m (9,843 ft) in (B2M1) 18 min, (B2M2)
12 min; range (B2M1) 960 nm (1,105 miles), (B2M2) 950 nm (1,094
miles).
Production: A total of 205 Type 89 aircraft (including 3
prototypes) were built by Mitsubishi Kokuki KK between October 1930
and 1935.
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