In 1938 a requirement was given for a four engine reconnaissance flying boat superior than the United Kingdom's Short Sunderland. To many, the H8K was the best flying boat used in World War II.
Specifications for the H8K called for an aircraft that could fly 5,000 miles at 210 mph and have a maximum speed of 280 mph.
The original design had retractable floats and a dorsal turret.
A mission for the H8K could last up to 24 hours.
The crew was protected by armor.
The wings were made from a metal frame and covering. There was a slight dihedral for better stability on long flights.
There were eight small fuel tanks located in the wings.
There were six fuel tanks that were located in the hull and were self sealing with carbon dioxide fire supression. The fuel was about 1/3 the total weight at takeoff.