Il bombardiere strategico Kawasaki Aircraft Industries Ki-91

Il Ki-91 era un bombardiere giapponese sviluppato dalla Kawasaki Aircraft Industries durante gli ultimi anni della seconda guerra mondiale.

Sviluppo

All'inizio del 1943, in seguito alla cancellazione del Nakajima Ki-68 e del Kawanishi Ki-85 a causa del fallimento della Nakajima G5N, Kawasaki  rispose al requisito dell'esercito imperiale giapponese per un bombardiere a lungo raggio di dimensioni e prestazioni simili alla B-29 Superfortress con il Ki-91. Come il G5N, il Ki-68 e il Ki-85, il Ki-91 doveva essere in grado di lanciare attacchi contro gli Stati Uniti continentali dal Giappone. Nell'aprile del 1944 fu costruito un modello in legno per lo sviluppo e, a maggio, fu ordinata la produzione del primo prototipo. La costruzione del prototipo iniziò a giugno, ed i primi raid di B-29 sul Giappone erano in corso a partire da quel mese. Nel febbraio del 1945, il primo prototipo del Ki-91 fu completato al 60% quando un raid aereo di B-29 danneggiò la struttura nella prefettura di Gifu dove il prototipo Ki-91 era in costruzione, portando il programma a una battuta d’arresto.

Design

Il Ki-91 era un progetto per un bombardiere pesante simile per dimensioni e carico di bombe alla B-29 Superfortress ed al Convair B-32. Aveva un'apertura alare ed una fusoliera più grandi rispetto ai B-29 e B-32 e presentava una cabina pressurizzata per consentire i voli ad alta quota. Tuttavia, al prototipo mancava una cabina pressurizzata, ma gli aerei di produzione sarebbero stati costruiti con la cabina pressurizzata. 

Specifiche

Caratteristiche generali:

• Equipaggio: 8
• Lunghezza: 32,97 m (108 ft 2 in)
• Apertura alare: 47,9 m (157 ft 2 in)
• Altezza: 9,99 m (32 ft 9 in)
• Superficie alare: 223,99 m 2 (2.411,0 piedi quadrati)
• Peso a vuoto: 33.999 kg (74.955 libbre)
• Peso lordo: 57.999 kg (127.866 libbre)
• Motopropulsore: 4 motori a pistoni radiali raffreddati ad aria Mitsubishi Ha-214 Ru da 18 cilindri, 1.900 kW (2.500 CV) ciascuno.
• Eliche: elica a 4 pale a velocità costante.

Prestazioni:

• Velocità massima: 580 km / h (360 mph, 310 kn) a 9.808 m (32.178 piedi)
• Autonomia: 9.000–10.000 km (5.600–6.200 mi, 4.900–5.400 nmi)
• Massimale di servizio: 13.500 m (44.300 piedi)
• Tempo all'altitudine: 8.000 m (26.000 piedi) in 20 minuti e 30 secondi.

Armamento:

• Guns:
• Mitragliatrici 12x 20 mm (0.787 in)
• Bombe: fino a 4.000 kg (8.800 libbre) di bombe.

ENGLISH

The Kawasaki Ki-91 represented a rare four-engine heavy bomber initiative of the middle-to-late war years for the Japanese Empire. The Ki-91 gained steam at a time when the Japanese military was reeling from consistent losses in-the-field and air supremacy was being lost on a month-to-month basis. It would seem prudent that fighters and interceptors would be the call of the day as it became in Germany but this four-engined "heavy" was still pushed through by Kawasaki.

The design was to feature a wingspan reaching 157.4 feet with a length of 108.2 feet - dimensionally larger than even the famous American Boeing B-29 "Superfortress" (141.2 foot wingspan, 99 foot length). Loaded weight was estimated at 127,870 pounds. The bombload was to be in the 8,820 lb range (decidedly less than the Superfortress' 20,000lb load limit) and the aircraft defensed by no fewer than 12 x 20mm cannons - two fitted to a nose turret, two in a dorsal turret, four across two ventral turrets (one forward, the other aft), and four to complete a turret at the tail - one of the best-armed bombers of the war to say the least. The large aircraft would be powered by 4 x Mitsubishi Ha-214 "Ru" engines developing upwards of 2,500 horsepower each and estimated performance specs included a maximum speed of 360 miles per hour with a ferry range out to 6,215 miles (the B-29 managed a speed of 360mph with a ferry range out to 5,600 miles).

 Outwardly, the aircraft was to be given a stepped cockpit approach meaning the flight deck sat out from the fuselage contours and held its own window panels (unlike the streamlined form of the B-29). The fuselage would be a rounded rectangle in profile with slab sides, the shape broken up some by the placement of several observation bubbles about her design. Glazing would be featured at the nose and around the cockpit with vision ports located throughout the rest of the fuselage and at gun positions. Mid-mounted monoplane wings were used, each featuring a pair of engine nacelles along their leading edges. The tail unit would consist of a single, rounded vertical fin coupled to a pair of low-mounted horizontal planes - these surfaces seated ahead of the tail turret. A tricycle undercarriage would be employed which was a departure of the "Tail dragger" configuration of old.

Design work on the aircraft began in May of 1943 and progress was such that by the end of 1944 the first prototype was being built while Kawasaki lines were gearing up for serial production. However, an Allied bombing raid during February 1945 destroyed much of what was to make the Ki-91 possible, forcing the program to be halted and ultimately abandoned in favor of fighters and interceptors to contend with the American B-29 presence over the Japanese homeland.

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