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Aichi S1A Denko

The Aichi S1A was designed as a Japanese night fighter to replace the Nakajima J1N1-S Gekkou.

Similar to the Gekkou, it was planned to have radar capabilities to defend against B-29 air raids over Japan.

However, due to challenges in addressing design flaws, such as the underpowered Nakajima Homare engines requested by the Navy, the development of the S1A took longer than expected, and no aircraft were finished before the end of the war.

The Denko’s service weight exceeded ten thousand kilograms due to the presence of special equipment such as oxygen injection.

However, the turbocharger’s distant placement from the engine led to numerous issues.

As the initial prototypes’ engines failed to meet Navy standards, only two aircraft were produced.

There were plans for two more aircraft, but they were ultimately cancelled.

These additional planes would have been equipped with the more potent Mitsubishi HI MK9A Ru or MK10A Ru engines.

Furthermore, in December 1944, the Tōnankai earthquake caused significant damage to the aircraft factories and prototypes.

Subsequently, on June 9, 1945, airstrikes targeted Aichi Kokuki and Aichi Tokei Denki Seizo Co. Ltd., resulting in the explosion of the S1A first prototype.

This incident compelled the relocation of the second prototype to the large Sadakazu factory in Gifu for assembly.

However, on July 9, another airstrike demolished the second prototype.





49 ft 6.5 in (15.1 m)


57 ft 5 in (17.5 m)


15 ft 1.5 in (4.61 m)

Wing area

505.902 sq ft (47.0 m2)

Empty weight

16,138 lb (7,320 kg)

Gross weight

22,443 lb (10,180 kg)

Max take-off weight

25,375 lb (11,510 kg)


2 × Nakajima NK9K-S,

2,000 hp (1,500 kW) each at take-off




Maximum speed

360 mph (580 km/h, 318 kn)

Cruise speed

273 mph (440 km/h, 240 kn)


1,054 mi (1,697 km, 916 nmi)

Ferry range

1,553 mi (2,500 km, 1,373 nmi)

Service ceiling

39,370 ft (12,000 m)

Wing loading

44.4 lb/sq ft (126.6 kg/m2)



2× fuselage mounted forward firing 30mm Type 5 cannon

2× fuselage mounted forward firing 20mm Type 99 model 1 cannon

2× dorsal turret mounted 20mm Type 99 model 2 cannon.


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