Aviation of World War II

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S1A Denko

Aichi S1A
  • Night Fighter
  • Aichi

S1A Denko. In the early years of the Pacific War, the command of the Imperial Navy Air Force did not feel the need for a specialized night fighter, so it showed no interest in developing such an aircraft. It was only in 1943 that the night flights of American B-17 and B-24 bombers against Japanese naval bases located in various areas of the Pacific theater of operations, and especially the strikes of B-29 heavy strategic bombers against targets on the territory of the Japanese islands, forced Kaigun Koku Hombu to take appropriate steps. . At first, they tried to adapt existing types of aircraft for use as night fighters. This is how special modifications of the D4Y2-S aircraft appeared. C6N1-S, P1Y1-S and J1N1-S. The latter achieved the greatest success in the role of night fighters, and it was these successes that prompted the military to develop, at the end of 1943, the design requirements of the 18-Xi Hei for a night fighter that would be able to effectively deal with B-29 bombers flying at high altitudes. To do this, a new aircraft equipped with a radar had to develop a speed of 685 km / h at an altitude of 9000 m and climb 6000 m in 8 minutes. In addition, he had to have powerful weapons, at least two 30-mm cannons. The maximum flight duration was 5 hours.

To implement the above requirements, Aichi was chosen, which at that time was not as heavily loaded with urgent orders as other aircraft manufacturers. The project, which received the factory designation AM-25 and the military S1A1 "Denko" (Ray of Light), was a twin-engine cantilever low-wing all-metal structure. The crew of the aircraft consisted of two people, with the pilot sitting in the front cockpit, closed with a teardrop-shaped lantern, and the workplace of the radar operator and gunner in one person was located inside the fuselage between the cockpit and the remotely controlled shooting tower. The small arms of the night fighter were very powerful and consisted of four cannons mounted in the front of the fuselage, and two mounted in a remote-controlled dorsal rifle turret of circular rotation. Interestingly, the latter were supposed to be used not for defense, but primarily for the destruction of enemy bombers flying above the fighter. This solution had a great advantage over the traditional method of installing guns for night fighters (stationary in the central part of the fuselage at an upward angle), since it did not require the pilot to aim the entire aircraft at the target and thus provided greater freedom of action when intercepting. The same purpose was served by the method of installing two 20-mm guns Type 99 Model 2 in the forward fuselage. They were mounted on a mobile machine and could be aimed upwards at an angle of up to 30 ° to the horizontal, which made it possible to fire at higher flying aircraft. Two more guns (Type 5 caliber 30 mm) were fixed in the nose of the aircraft. Additionally, the S1A1 could carry one 250 kg bomb or four 60 kg phosphorus bombs on its fuselage. Instead of bombs, it was possible to hang two additional drop fuel tanks with a capacity of 700 liters each.

It was originally supposed to use two radial engines Nakajima NK9K-S Homare 22 as a power plant, but it turned out that they do not develop their design power at high altitudes. This made it possible to achieve a top speed of just 589 km/h, much less than the 18-Ci Hei specification required. Only the use of improved Homare 24 engines equipped with turbochargers made it possible to hope for a speed of 679 km / h. But it was not possible to verify the correctness of the calculations in practice. Two prototypes commissioned by Kaigun Koku Hombu were destroyed in two American bombing raids on Nagoya, during which the Aichi plant at Eitoku was also damaged. The first of the prototypes by this time was 70% ready, the second - 90%. Therefore, it is very difficult to assess the possible combat effectiveness of the S1A1, the first and only night fighter of Japan's naval aviation, originally designed for use in this role. Its design, of course, is very interesting and is characterized by a number of innovative solutions, but it would be possible to bring them “to mind” is a big question.

Aichi S1A1
Crew 2
Wing span, m 17.50
Wing area, m² 47.00
Length, m 15.10
Height, m 4.61
2 × PE Nakajima NК9К-S Homare-22
power, hp 2×2000
Weights, kg
Empty weight 7,320
Loaded weight 10,180
Gross weight 11,510
Maximum speed, km/h 580
Cruise speed, km/h 440
Rate of climb, m/min 610
Service ceiling, m 12,000
Servicre range, km 1,700
Ferry range, km 2500

Armament. Two 30 mm "type 5" cannons and two 20 mm "type 99 model 2" cannons forward and two 20 mm "type 99 model 2" cannons in the upper turret.

Construction. The low-lying all-metal wing of the S1A consisted of a center section and trapezoidal consoles with rounded tips. Cantilever tail of classical design.

The S1A fuselage had an all-metal construction and was characterized by a small cross-sectional area. Hemispherical canopy of the gunner's cockpit, who was also the radar operator. Four cannons were installed in the forward fuselage: two 30 mm Type 5 - fixed and two 20 mm Type 99 Model 2 - on a mobile machine, which allowed them to be directed upwards at an angle of up to 30 °.

The main landing gear in flight retracted into the engine nacelles, the tail strut retracted into the fuselage.

Nakajima SK9K-SHomare 22 18-cylinder air-cooled engines with 2000 hp. rotated four-blade variable-pitch propellers with a diameter of 3.45 m.

Photo Description
Aichi S1A

Drawing Aichi S1A


  • Japan float aircraft /Evgeniy Aranov/
  • "Japan Aircraft of World War II." /Oleg Doroshkevich/
  • Aviation of Japan /Andrey Firsov/