Tuesday, February 24, 2015
Although first conceived as early as 1939, the Tachikawa Ki-74 had not been placed in full production when the Pacific war ended. During those six years its intended role had been changed from that of long-range reconnaissance to that of long-range stratospheric bombing.
Under the guidance of Dr Kimura, the Ki-74 was originally designed in the spring of 1939 to meet the requirements of a specification issued by the Koku Hombu and calling for a long-range reconnaissance aircraft capable of operating west of Lake Baikal from Manchurian bases. The aircraft was to have a range of 5,000 km (3,107 miles) at a cruising speed of at least 450 km/h (280 mph). To meet these performance requirements, Dr Kimura proposed using a pair of 2,400 hp Mitsubishi Ha-214M radials driving six-blade propellers. and fitting a pressure cabin. However, pending development of the pressure cabin system tested on the Tachikawa SS-1 and A-26/Ki-77, the project was temporarily suspended.
Late in 1941 the project was revived as a long-range high-altitude bomber-reconnaissance aircraft capable of bombing the United States mainland. To fit the aircraft for its new role, Tachikawa added bombing equipment, self-sealing fuel tanks and armour to the original design and decided to replace the Ha-214M engines with a pair of Mitsubishi Ha-211-I radials, rated at 2,200 hp for take-off, 2,070 hp at 1,000 m (3,280 ft) and 1,720 hp at 9,500 m (31,170 ft). The design of the aircraft was approved by the Koku Hombu in September 1942 and construction of three prototypes was authorised. The first prototype, completed in March 1944, was followed by two externally identical aircraft which were powered by a pair of turbosupercharged Ha-211-I Ru radials, rated at 2,200 hp for take-off, 2,070 hp at 1,000 m (3,280 ft) and 1,720 hp at 9,500 m (31,170 ft). However, during the flight trial programme both versions of the Mitsubishi Ha-211 suffered from teething troubles and it was decided to replace them on the pre-production aircraft with the lower-powered but more reliable turbosupercharged Mitsubishi Ha-104 Ru radials, rated at 2,000 hp for take-off, 1,900 hp at 2,000 m (6,560 ft) and 1,750 hp at 6,000 m (19,685 ft).
Thirteen Ha-104 Ru powered pre-production aircraft were built and were still undergoing tests when the war ended. All five crew members were seated in a pressure cabin in the forward fuselage, and the aircraft was armed with a single remotely-controlled 12.7 mm (0.5 in) machine-gun in the tail and carried a bomb-load of 1,000 kg (2,205 lb). Plans were made to use the Ki-74s in bombing attacks against B-29 bases at Saipan as soon as sufficient aircraft were available, but the Japanese surrender terminated the project. Although the Ki-74 was never encountered during the war, the Allies were aware of its development, but thinking at first that it was a 'super-range, high-speed fighter' intended for long-range escort duty they accordingly assigned to it a male name: 'Pat'; when the true role of the aircraft was discovered the code-name was changed to 'Patsy'.
The fourth pre-production aircraft (Ki-74 c/n 7) was modified in 1944 to undertake non-stop flights between Japan and Germany, but the Third Reich capitulated before the first of these flights could be made. Other developments included a pure bomber version, the Ki-74-II with the bomb-load increased to 2,000 kg (4,410 lb), and a transport version, but both these projects were abandoned before completion.
Manufacturer: Tachikawa Hikoki KK (Tachikawa Aeroplane Co Ltd).
Type: Twin-engined high-altitude long-range reconnaissance-bomber.
Crew (5): Enclosed in pressure cabin.
Powerplant: (1st prototype) Two Mitsubishi Ha-211-I eighteen-cylinder air-cooled radial engine, driving four-blade metal propellers, (2nd and 3rd prototypes) two Mitsubishi Ha-221-I Ru eighteen-cylinder air-cooled radial engines, driving four-blade metal propellers, (4th-16th aircraft) two Mitsubishi Ha-104 eighteen-cylinder air-cooled radial engines, driving four-blade metal propellers.
Armament: One remotely-controlled 12.7 mm (0.5 in) Type 1 (Ho-103) machine-gun. Bomb-load: 1,000 kg (2,205 lb).
Dimensions: Span 27 m (88 ft 7 in); length 17.65 m (57 ft 10 7/8 in); height 5.1 m (16 ft 8 25/32 in); wing area 80 sq m (861.11 sq ft).
weights: Empty 10,200 kg (22,487 lb); loaded 19,400 kg (42,770 lb); wing loading 242.5 kg/sq m ( 49.7 lb/sq ft); power loading 4.4 kg/hp (9.7 lb/hp).
Performance: maximum speed 570 km/h (354 mph) at 8,500 m (27,890 ft) cruising speed 400 km/h (249 mph) at 8,000 m (26,245 ft); climb to 8,000 m (26,245 ft) in 17 min; service ceiling 12,000 m (39,370 ft); range 8,000 km (4,971 miles).
Production: A total of 16 Ki-74s were built by Tachikawa Hikoki KK between march 1944 and August 1945.