Kawanishi H6K (Mavis) - 九七式飛行艇:
The 934 Kokutai was formed on November 1, 1942 when it changed its name from 36Ku. It was a seaplane reconnaissance and interceptor unit mostly equipped with Mitsubishi F1M “Pete”, Aichi E13A “Jake” but also with Mitsubishi A6M2-N “Rufe”. On July 4, 1942 the unit advanced to Ambon island in Indonesia and on May 1, 1943 a single Kawanishi H6K “Mavis” was attached to the unit for transport duties. Pilot of this "Mavis" was Kitaide Daita.
During his time in Ambon with the 934Ku Kitaide-san usually flew transport missions with his “Mavis” which was purely a transport flying boat and didn’t carry any offensive equipment; not even bomb racks. So when occasionally enemy submarines were spotted, there was very little for the crew and plane to do. Following a request to the unit commander it was decided for the flying boat to carry one small size, 60kg, bomb during these transport missions with the fuse removed to avoid accidents. In order to “bomb” an enemy target two observers would have to carry the bomb to the tail gunner’s position, install the fuse and drop the bomb when the pilot would give them the sign with a buzzer.
One such occasion was on the 18th of June 1943 when Kitaide-san received orders to transport cargo from Ambon to Surabaya in Java, a route which was not often visited by enemy planes and was a relatively safe one. While enjoying a cup of hot coffee with the auto-pilot having taken over, the crew noticed a beautiful rainbow. At the edge of the rainbow near the Kangean island the waves of a ship were visible. Flying at an altitude of a few thousand meters, Kitaide-san grubbed his binoculars and saw that it was actually an enemy submarine, confirmed by information that no friendly submarines were located in the area. He immediately gave an order for the two observers located in the front of the flying boat to gather and rush to the rear end. His instructions were to prepare the bomb and press the buzzer twice when they were ready, while he would hit the buzzer once to give them the signal to drop the bomb. And to be extra careful how to handle the fuse!
Kitaide-san brought his “Mavis” to a dive with the enemy submarine becoming gradually bigger in the windscreen. The submarine crew suddenly realising the enemy flying boat started for a crash dive the whole situation turning into a contest who would dive faster... At about 300 meters and when the coning tower of the submarine was clearly visible he pressed the buzzer and the rear crew released the bomb. At the same time he swiftly banked to the starboard gaining altitude and getting out of the dive he watched the bomb falling towards the submarine from his side window. The bomb could explode only on impact and exactly when the conning tower was about to get underwater, it hit it. A big explosion with a huge fireball and black smoke were clear indications that it was a direct hit. A few seconds later the dark rear end of the submarine appeared out of the water and slowly the submarine started sinking leaving only the calm emerald waters behind while the "Mavis" crew were wondering if what they had seen was actually true. A dark oil spot was all that was left to indicate the sunk submarine…
Extract from the book: ""Kiseki No Hikotei" (The Miracle Flying Boat)