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The Aichi S1A Denko (Bolt of Light) was a Japanese Navy night fighter that was at an advanced stage of development before US bombing destroyed the two prototypes, effectively ending the programme.
The Japanese Navy issued a specification for a night fighter late in 1943. This called for an aircraft with a top speed of 426mph at 29,530ft, a rate of climb of 8 minutes to 19,685 and an endurance of 5 hours. The new aircraft was to be armed with two 30mm cannon and it was to carry airborne radar.
Aichi responded with a twin-engined two-man aircraft with the designation Navy Experimental 18-Shi Night Fighter Denko (Bolt of Light). The basic layout was fairly conventional. The thick tapered wings were low mounted. The engines were carried below the wings, with the retractable landing gear sharing the nacelles.
More advanced features were built into the wings, which had drooping ailerons that could act as extra landing flaps and air breaks to prevent the fighter from overshooting its target.
The S1A was to be armed with two 30mm Type 5 and two 20mm Type 99 Model 2 cannon carried in the lower forward fuselage and two rearward firing 20mm Type 99 Model 2 cannon in a remotely controlled turret between the radar operator and the tail.
The crew of two were given separate cockpits. The pilot had a long canopy over the wing leading edge. The radar operator/ rear gunner was at the trailing edge, with a small dome over his position.
Aichi and the Japanese Navy disagreed over the correct engine to use. The Navy favoured the Nakajima Homare engine, but this didn't perform well at altitude. Top speed with two 2,000 NK9K-2 Homare 22 twin-row radial engines was estimated at 391mph early in the design process, then dropped to 366mph. If turbosupercharged Homare 24 engines had been available, a top speed of 422mpg was estimated.
Two prototypes were under construction, and both reached quite an advanced stage before being destroyed in Allied bombing raids. The first prototype was 70% complete and the second 90% complete. No replacement prototypes were produced and the type never flew.
Performance estimates
Engine: Two Nakajima NK9K-S Homare 22 eighteen cylinder air-cooled radial engines
Power: 2,000hp each at take-off, 1,885hp each at 5,740ft, 1,620hp each at 21,000ft
Crew: 2
Span: 57ft 31/32in
Length: 49ft 6 1/2in
Height: 15ft 1 1/2in
Empty weight: 16,138lb
Loaded weight: 22,443lb
Maximum take-off weight: 25,375ft
Max speed: 366mpg at 26,245ft
Climb Rate: 14min 45sec to 29,530ft
Service ceiling: 39,370ft
Normal range: 1,054 miles
Maximum range: 1,580 miles
Armament: Two forward firing 30mm cannon, two forward firing 20mm cannon and two rear firing 20mm cannon
Bomb load: 551lb