Development and Service Record
Development and Service Record
The Kawanishi H6K 'Mavis' was a long range flying boat that demonstrated that Kawanishi could complete with the best in the world, and that despite its lack of protection remained in front line service throughout the Second World War.
The H6K was designed as a result of a 8-Shi specification for a large flying boat issued by the Japanese navy in 1933. Kawanishi proposed two designs in response to this aircraft, the Type Q and Type R. Neither satisfied the Navy, and in 1934 a modified 9-Shi specification was issued. The new aircraft was to have a range of 2,500 nautical miles and a cruising speed of 120 knots.
Kawanishi responded with their Type S, a parasol wing four engined flying boat. The Kawanishi H6K had a remarkable resemblance to the Sikorsky S-42. Both shared the same basic layout, with a parasol wing carrying four engines, similar arrangements of wing struts and similar twin vertical tails. The wings were also similar, with straight centre sections and tapering tips. The differences were in the details - the H6K had a rather smaller tail than the S-42, its wings had a slight dihedral, and the fine details of wing shape and tail shape were different. The H6K was also a much larger aircraft, eighteen feet longer, with a thirteen foot wider wingspan, and was significantly faster, with a top speed of 239mph, fifty miles faster than the S-42. During the Second World War the Allies considered the H6K to be a copy of the Sikorsky aircraft, but other than the basic shape the aircraft were different.
The first prototype made its maiden flight on 14 July 1936, powered by four 840hp Nakajima Hikari 2 nine-cylinder air cooled radial engines. The original design had a number of flaws, most notable with the water handling and a lack of engine power. The first was solved by moving the forward step back by 50cm, and the second by installing 1,000hp Mitsubishi Kinsei 43 engines on the first, third and fourth prototypes. The modified aircraft was accepted for service as the H6K1 Navy Type 97 Flying Boat and entered production as the H6K2 Navy Type 97 Flying Boat Model 2.
The H6K made its combat debut during the war in China. Sixty six were in use with first line units at the start of the Pacific War. As well as its original long range reconnaissance role, the H6K was used for very long range bombing missions, attacking targets in the Dutch East Indies and on Rabaul. This second role soon had to be abandoned in the face of more capable Allied fighters, which could take advantage of the aircraft's lack of armour or self sealing fuel tanks, but it was still able to operate as a maritime reconnaissance aircraft, operating over the vast expanses of the Pacific in areas free from Allied fighters.
H6K1 Navy Type 97 Flying-Boat Model 1
This designation was given to the first, third and fourth prototypes after they were re-engined with the 1,000hp Mitsubishi Kinsei 43 fourteen-cylinder air cooled radials. The H6K1 entered service in January 1938.
H6K2 Navy Type 97 Flying-Boat Model 2 (Model 11 from April 1941)
This designation was given to the first ten production aircraft. They were virtually identical to the H6K1s, but with minor equipment changes.
The H6K3 was the designation given to two aircraft built as staff transports.
H6K4 Navy Type 97 Flying-Boat Model 2-2
The H6K4 was the first major production version. It used the same engines as the H6K2, but the fuel capacity was almost doubled, from 1,708 gallons up to 2,950 gallons. It was armed with one hand operated 20mm cannon in the tail turret and 7.7mm machine guns in the two beam positions, and the open bow and dorsal positions. In August 1941 the engine was changed to the Kinsei 46 and the designation became the H6K4 Model 2-3. Later both versions were redesignated as the Model 22. A total of 127 H6K4s were built between 1939 and 1942.
H6K2-L Navy Type 97 Transport Flying Boat ('Tillie')
The H6K2-L was a transport aircraft based on early production H6K4s. All guns were removed, and the fuselage was modified to carry a small amount of cargo and two passenger compartments - one with ten seats and one with eight seats or four beds. Sixteen H6K2-Ls were built, along with two earlier conversions of the H6K2.
H6K4-L Navy Type 97 Transport Flying Boat
The H6K4-L was a second transport version, this time powered by the Kinsei 46 engine. The H6K4-L was otherwise similar to the H6K2-L, but with extra cabin windows. Twenty were built and two converted from existing H6K4s.
The H6K5 was the final production version, and was developed to safeguard against any problems with the new Kawanishi H8K1. The H6K5 was powered by four 1,300hp Mitsubishi Kinsei 51 or 53 radial engines, and was given a nose turret in place of the original open gun position on earlier versions.
Engine: Four Mitsubishi Kinsei 43 or 46
Power (Kinsei 43): 1,000hp at sea level, 990hp at 9,185ft
Power (Kinsei 46): 930hp at sea level, 1,070hp at 13,780ft
Wing span: 131ft 2 23/32in
Length: 84ft 0 27/32in
Height: 20ft 6 27.32
Empty Weight: 25,810lb
Loaded Weight: 37,479lb
Max Speed: 211mph at 13,125ft
Cruising Speed: 138mph at 13,125ft
Service Ceiling: 31,530ft
Range: 2,981 miles
Armament: One 20mm cannon in tail, 7.7mm machine guns in bow, dorsal and two beam positions
Bomb-load: Two 1,764lb torpedoes or 2,205lb of bombs