TYPE: Night fighter
ACCOMMODATION: Crew of two
POWER PLANT: Two Nakajima NK9K-s radial engines, rated at 2,000 hp each
PERFORMANCE: 360 mph
COMMENT: The Aichi S1A “Denko” (“Bolt of Light”) was a Japanese night fighter, intended to replace the Nakajima J1N1-S “Gekko” (“Moonlight”, Allied code name “Irving”). It was to be, like the “Gekko”, equipped with radar to counter the B-29 air raids over the Japan. Development time increased while trying to overcome design shortcomings, such as the insufficient power of the Navy’s requested Nakajima “Homare” engines, resulting in no aircraft being completed before the war ended.
Because it was full of special equipment the “Denko’s” service weight exceeded ten thousand kilograms. Some of this specialized equipment included oxygen injection but the turbocharger’s remote location from the engine caused many problems. Because the initial prototypes’ engines did not pass Navy standards only two were ever manufactured. Two more had been planned before cancellation that would have used the more powerful Mitsubishi HI MK9A Ru or MK10A Ru engines.
Additionally, Tonokai earthquake occurred in December 1944 and the aircraft factories and prototypes were badly damaged. On 1945 June 9 the airstrikes on Aichi Kokuki KK and Aichi Tokei Denki Seizo Co, Ltd blew up the first prototype and forced movement of the second to the Gifu large Sadakazu factory to be assembled. But on July 9 of that year another airstrike destroyed the second prototype. At that time Aichi S1A “Denko” was the most massive fighter developed in Japan’s naval history (Ref.: 24).