Aichi M6A1 “Seiran”
Japanese World War II Navy Special Attack Bomber

Archive Photos ¹

[Aichi M6A1 “Seiran” (Clear Sky Storm), National Air and Space Museum Steven F. Udvar-Hazy Center, Chantilly, Virginia, 02-16-2004, Photos by Jim Hough ¹]

[Aichi M6A1 “Seiran” (Clear Sky Storm) Historic Photos from Wikipedia ²]

Overview ²

  • Aichi M6A1 “Seiran” (Clear Sky Storm)
  • Role: Submarine-launched dive bomber
  • Manufacturer: Aichi Kokuki KK
  • First flight: 1943
  • Introduced: 1945
  • Retired: 1945
  • Primary user: IJN Air Service
  • Produced: 1943-1945
  • Number built: 28

The Aichi M6A “Seiran” (Clear Sky Storm) was a submarine-launched attack floatplane designed for the Imperial Japanese Navy. It was intended to be used with the I-400 class submarine, a 4,082 tonne (4,500 ton) submarine aircraft carrier. Two or three of the craft would be stowed aboard in disassembled form, and launched by catapult. The twin floats could be jettisoned, and the aircraft was essentially meant to be ditched at sea upon completion of its mission. The Type AM submarine was also intended to carry two of these aircraft.

An alternate version with landing gear instead of floats was designated M6A1-K and named Nanzan (Southern Mountain). While generally described as a land-based trainer, some sources indicate that it was designed for the attack role, to be launched from the submarine and then landed. Besides the difference in landing gear, the vertical stabilizer's top portion, which was foldable on the Seiran, was removed.

Operational History ²

The first M6A1 was completed in November 1943, and 28 examples (including M6A1-Ks) were completed by 1945. Admiral Isoroku Yamamoto made plans back in early 1942 to launch a surprise air strike on the Panama Canal using the Seiran. The target was later changed in 1945 to the American aircraft carriers stationed at Ulithi Atoll following Yamamoto's death and reports of an impending attack on the home islands.

This mission was assigned to the 1st Submarine Flotilla, which comprised two submarines, the I-400 and the flagship I-401, each carrying three Seirans. The flotilla departed Japan on 23 July 1945 and proceeded towards Ulithi. However, on 15 August, the flagship I-401 received a radio message from headquarters, informing them of Japan's surrender. They were ordered to return to the nearest port in Japan, ending the flotilla's first and only mission, and preventing the Seiran from ever entering combat. All six Seirans onboard the two submarines were catapulted into the sea with their wings and stabilizers folded to prevent capture by the Americans.

Variants ²

  • M6A1 Prototype: Prototypes powered by Atsuta 30 or 31 1,044 kW (1,400 hp) engine and removable floats, 8 built.
  • M6A1 Seiran: Special Attack Bomber, 18 built.
  • M6A1-K Nanzan: Prototypes of training version, retractable wheeled landing gear, 2 built.
  • M6A2: Prototype, equipped with one 1,163 kW (1,560 hp) Mitsubishi Kinsei MK8P 62 of driving a three-blade, constant-speed metal propeller, 1 built.

Operators ²

  • Japan: Imperial Japanese Navy Air Service

Survivors ²

A single M6A1 has been preserved and resides in the Udvar-Hazy Center of the Smithsonian's National Air and Space Museum. It is located in the Washington, DC suburb of Chantilly, VA near Dulles International Airport.

Aichi M6A1 “Seiran” Specifications and Performance Data ³

General Characteristics

  • Crew: 2
  • Length: 11.64 m (38 ft 2.25 in)
  • Wingspan: 12.26 m (40 ft 2.75 in)
  • Height: 4.58 m (15 ft 0.31 in)
  • Wing area: 27.0 m² (291 ft²)
  • Empty weight: 3,301 kg (7,277 lb)
  • Loaded weight: 4,040 kg (8,907 lb)
  • Max takeoff weight: 4,445 kg (9,800 lb)
  • Powerplant: 1 × Aichi Atsuta Type 31 liquid-cooled, inverted V12 cylinder, 1,044 kW (1,400 hp)


  • Maximum speed: 474 km/h (256 knots, 295 mph) at 5,200 m (17,060 ft)
  • Cruise speed: 296 km/h (160 knots, 184 mph) at 3,000 m (9,850 ft)
  • Range: 1,190 km (642 nm, 739 miles)
  • Service ceiling: 9,900 m (32,500 ft)
  • Climb to 3,000 m (9,850 ft)


  • Guns: 1 × 13 mm cabin-mounted Type 2 machine gun
  • Bombs: 1 × torpedo or 2 × 250 kg (551 lb) or 1 × 850 kg (1,874 lb) bombs


  • Hough, Jim. “Aichi M6A1 “Seiran”,” The Skytamer Archive, Photos by Jim Hough copyright © 2/16/2004 by Skytamer Images. All Rights Reserved
  • Wikipedia, the free encyclopedia. Aichi M6A
  • Gunston, Bill (foreward). “Jane's Fighting Aircraft of World War II (reprint)”, Crescent Books, ISBN 0 517 67964 7, 1995

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