The first production model of the H8K series was the H8K1. It had a crew of ten and four Mitsubishi MK4B Kasei 12 Engines that were capable of propelling the H8K at speeds of up to 433 km/h.
The H8K also had a defensive armament of two 20mm autocannons and four 7.7mm MGs, along with the capability to carry up to 2,000 kg of bombs or two torpedoes. The H8K was about 28 metres long with a wingspan of 38 metres. Total weight was about 15,400 kg. The service ceiling of the Kawanishi was 8,770 metres while the maximum range was 7,200 km.
The H8K was well protected, featuring armor protection that could withstand quite a beating. The fuel was also kept in six separate tanks onboard and there was enough fuel to last up to 20 hours, more than long enough for a standard patrol.
Codenamed "Emily" by Allied forces, The H8K was known as the "Flying Porcupine", especially in the H8K2 variant, because of the large defensive armament. (The Short Sunderland was also known by this nickname for the same reason) Despite the fact that the H8K was a flying boat, it had small wheels that could be deployed for landings on land.
The H8K had several variants, the most produced version being the second variant, the H8K2. The first variant, the H8K1-L, also known as the Seiku (Clear Sky) Transport Flying Boat Model 22, was the transport variant of the series, and could carry up to 64 passengers. It also had Mitsubishi MK4Q Engines and a smaller armament. The next variant, the H8K2, had many modifications that made it the most successful of the series.
The first of these modifications is the fact that it had a total of five 20mm autocannons and three 7.7mm MGs spread throughout the aircraft. It also had four new Mitsubishi MK4Q Kasei 22 Engines that were more powerful than the earlier models. Some H8K2s were even equipped with ASV Radar, making them even deadlier. The next variant of the H8K series was the H8K3 and it had additional armor protection added along with the floats modified to be retractable. The next and final variant of the series was the H8K4 which was fundamentally the H8K3 only it had Kasei 25b Engines installed.
The H8K was developed in 1938/1939 and had its first flight in 1941. The prototype had several problems when landing on water, particularly stability and so it was modified until it finally was ready for service in 1942. The H8Ks first mission was carried out in 1942 and it was known as Operation K. Two H8Ks were to bomb Oahu, Hawaii, but due to bad weather, all the bombs missed their targets, only four actually hitting the island.
However, the attack did renew American fears of Japanese raids. During the war, H8Ks also served in the anti-submarine role and in fact sunk several US submarines. The H8K also engaged in reconnaissance missions and due to heavy armament, long range, and radar, the H8K is considered by many, the best flying boat of WWII.
- Gunston, Bill (Forward). Jane's Fighting Aircraft of World War II. Tiger Books. 1989. ISBN 1-85501-996-5. (Reprint of Jane's All The World's Aircraft 1945/1946. Bridgeman, Leonard (Editor). 1946).
- Lüdeke, Alexander. Weapons of World War II. Parragon Books Ltd. 2007. ISBN 140750195X