Tuesday, February 24, 2015

Mitsubishi B2M1 and 2 Navy Type 89 Carrier Attack Aircraft - Part 2

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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