Engineering:Tachikawa Ki-77

Short description: Japanese experimental long-range aircraft

Ki-77
Tachikawa Ki-77 in U.S. markings, 1945
Role	Long-range experimental aircraft
National origin	Japan
Manufacturer	Tachikawa Aircraft Company
First flight	18 November 1942
Retired	1945
Primary user	Imperial Japanese Army Air Service
Number built	2

The Tachikawa Ki-77 was a Japanese very long-range experimental transport and communications aircraft of World War II derived from a design commissioned by a newspaper to break the flight distance record set by a rival. It was a low-wing cabin monoplane with twin piston engines and a tailwheel undercarriage.

Development

The Ki-77 was the Japanese Army Air Force designation for the A-26, a clean, slim low-wing, twin-engine monoplane intended for an endurance flight between New York and Tokyo. The A stood for the name of the sponsor, a newspaper Asahi Shimbun which was vying for records with a rival paper that had sponsored the Mitsubishi Ki-15 Kamikaze flight to the United Kingdom in 1937. 26 was for the 26th century of the Japanese Imperial Dynasty - 1940 was year 2600 in the Japanese calendar.

The Ki-77's overall design was developed under the aegis of Dr. Hidemasa Kimura of the Aeronautical Research Institute of the University of Tokyo, with Tachikawa Aircraft Company being responsible for manufacturing and detail drafting work. The aircraft's layout was finalized in autumn of 1940 with its first flight originally expected in late 1941, but this was canceled with the start of war against the United States and consequent reallocation of priorities. The Ki-77 design included a number of novel features, including a high aspect ratio laminar flow wing for reduced drag, a sealed but unpressurized cabin to reduce the need for oxygen masks at its intended operating altitude, and special low drag cowlings.

Flight from Japan to Germany

In response to a flight made by an Italian Savoia-Marchetti S.M.75GA which flew to Japan in July 1942 with stops in Russia and China, the Japanese decided to forge a link with Europe, but wished to avoid Soviet-controlled airspace. The easiest route was that taken by the Italians, following the great circle route, but General Tojo opposed this because it implied a violation of Soviet airspace. Japan was not at war with the Soviets and Tojo wished to avoid either provoking them or asking their permission. Development work was restarted on the A-26/Ki-77 project, and the first of two prototypes flew on 18 November 1942. The prototype suffered from persistent oil cooling problems which required many changes before being solved, delaying further flights into July 1943; while working on these engineering issues, Tachikawa built a second aircraft.

Colonel Saigo considered the so-named "Seiko" (Success) mission absurd and suicidal, but the crew was aware of the hazards of the mission; they even had a personal dose of poison to kill themselves if forced down in enemy territory. The pilot was Juukou Nagatomo, the co-pilot was Hajime Kawasaki, Kenji Tsukagoshi and Noriyoshi Nagata were flight engineers, and Motohiko Kawashima was the radio operator. Three Army officers were also carried as passengers, two of whom were military attachés. They departed Japan on 30 June 1943 for Singapore, where the airstrip had to be lengthened by 1,000 meters to assure a safe takeoff. Finally, the aircraft took off at 7:10 on 7 July 1943 with eight tons of fuel, ample to reach Europe.

Their intended destination was the German airfield at Sarabus (now Hvardiiske, Crimea, [ ⚑ ] 45.118236°N 33.976564°E / 45.118236; 33.976564.) but they were to disappear over the Indian Ocean. British fighters likely intercepted them as they were aware of the flight and its route (via air grid squares 3420, 2560 and 2510) thanks to the ULTRA analysts at Bletchley Park decoding intercepted German communications to Sarabus warning of their impending arrival. Slow, unarmed, without armour protection and with a substantial amount of fuel on board, the Ki-77 would have been vulnerable to Allied fighters, even had no mechanical problems occurred.

Endurance record flight

Japan carried out a second flight to gain an endurance record and to verify the Ki-77's capabilities. The existing record had been held by Italy's Savoia-Marchetti SM.75GA since 1939. thumb|Captured Ki-77 aboard USS Bogue Even if the usefulness of record breaking flights was overshadowed in 1944 by the necessities of war, the Japanese needed a propaganda coup and the surviving Ki-77 was available. On 2 July it flew 19 circuits over a triangular route off Manchuria, landing 57 hours 9 minutes later and covering 16,435 km (10,212 mi) at an average speed of 288.2 km/h (179.1 mph), 3,499 km (2,174 mi) more than the SM.75's 12,936 km (8,038 mi) record. The Ki-77 landed with 800 liters remaining in the tanks of the 12,200 L (2,700 imp gal; 3,200 US gal) it began with, so the maximum endurance was around 18,000 km (11,000 mi). The Ki-77's endurance record was first exceeded in October 1946 by a Lockheed P2V-1 Neptune in a flight from Perth, Australia to Columbus, Ohio in the American midwest, of over 18,083.6 km (11,236.6 mi).

The distance record Ki-77 aircraft was still in existence when Japan surrendered and was shipped to the United States aboard the United States Navy escort carrier USS Bogue from Yokosuka in December 1945, arriving at Alameda, California on 8 January 1946 for examination before being scrapped.

Operator

Japan

Imperial Japanese Army Air Service

Specifications (Tachikawa Ki-77)

Data from Japanese Aircraft of the Pacific War

General characteristics

• Crew: 5
• Length: 15.3 m (50 ft 2 in)
• Wingspan: 29.438 m (96 ft 7 in)
• Height: 3.85 m (12 ft 8 in)
• Wing area: 79.56 m² (856.4 sq ft)
• Empty weight: 7,237 kg (15,955 lb)
• Gross weight: 16,725 kg (36,872 lb)
• Fuel capacity: 11,155 L (2,454 imp gal)
• Powerplant: 2 × Nakajima Ha-115 14-cyl two-row air-cooled radial piston engines, 870 kW (1,170 hp) each for take-off
  
  • 745.7 kW (1,000 hp) at 4,300 m (14,108 ft)
• Propellers: 3-bladed metal constant speed propellers

Performance

• Maximum speed: 440 km/h (270 mph, 240 kn) at 4,600 m (15,092 ft)
• Cruise speed: 300 km/h (190 mph, 160 kn)
• Range: 18,000 km (11,000 mi, 9,700 nmi)
• Service ceiling: 8,700 m (28,500 ft)
• Time to altitude: 6,000 m (19,685 ft) in 24 minutes
• Wing loading: 210.2 kg/m² (43.1 lb/sq ft)
• Power/mass: 0.104 kW/kg (0.063 hp/lb)

See also

• Messerschmitt Me 261 Adolfine

References

Bibliography

• Flude, Ray (2018). "Berlin or Bust: Japan's Tokyo–Berlin Attempt, 1943". The Aviation Historian (25): 44–53. ISSN 2051-1930. 
• Francillon, René J. Japanese Aircraft of the Pacific War. London: Putnam Aeronautical, 1979. ISBN:0-370-30251-6. (new edition 1987. ISBN:0-85177-801-1.)
• Nakazawa, Akinori and Strippoli, Roberta, '1942-43: Italiani e Giapponesi in volo per rafforzare l'Asse Roma-Tokyo', Rivista Storica magazine Coop Giornalisti Storici, Rome, n.7/94, p. 48-53