M6A Seiran, Japanese Light Bomber

Photograph of M6A Seiran submarine seaplane
U.S. Navy. Via Wikipedia Commons

Aichi M6A Seiran ("Mountain Haze")


Crew Two in tandem cockpit
Dimensions 40'3" by 38'2" by 15'0"
12.26m by 11.64m by 4.58m
Wing area 291 square feet
27 square meters
Weight 7277-9800 lbs
3301-4445 kg
Speed 295 mph at 17,060 feet
475 km/h at 5200 meters
Cruising speed       184 mph at 9.845 feet
296 km/h at 3000 meters
Climb rate 28 feet per second
8.6 meters per second
Ceiling 32,480 feet
9900 meters
Power plant One 1400hp (1044 kW) Aichi AE1P Atsuta 30 12-cylinder inverted-V liquid cooled engine driving a constant speed three-blade metal propeller.
Armament One flexible 13mm Type 2 machine gun in the rear cockpit
Bomb load
2 250 kg (551 lb) bombs or 1 850 kg (1874 lb) bomb or 1 800 kg (1760 lb) torpedo
Range 642 nautical miles (1190 km)
Production A total of 28 A6Ms were built at Aichi Kokuki K.K., Eitoku:
  6 M6A1 prototypes (1943-10 to 1944-10)
  20 M6A1 production aircraft (1944-10 to 1945-7)
  2 M6A1-K trainer prototypes (1945)
The M6A1-K was a trainer with retractable landing gear.

The M6A Seiran was built specifically for use on the Sen-toku class aircraft carrying submarines. The original specifications called for a fast aircraft without an undercarriage, but the design was revised to use twin detachable floats. The wings and tail surfaces could be tightly folded for stowage and, in spite of their complexity, the aircraft could be prepared for flight in less than 7 minutes. Its performance was comparable with land-based light bombers and it might well have been able to penetrate the defenses of its intended target, the Panama Canal.

A squadron of these aircraft were to be launched from south of the Panama Canal, fly east and north of the canal at low altitude to evade radar, then turn back south to attack the gates of the Gatun Locks on the Atlantic side with torpedoes. The Japanese estimated that destruction of the gates would disable the canal for six months. Due to a lack of skilled torpedo pilots, the attack plan was subsequently changed so that only two aircraft would use torpedoes and the rest would make a glide bombing attack. In 1945 the plan was further changed to a kamikaze attack.

However, by the time the aircraft and submarines were ready, the fortunes of war had turned so badly against the Japanese that attacks on either the Panama Canal or the U.S. West Coast were ruled out as useless gestures. The mother submarines with their aircraft were deployed instead against Ulithi Atoll, the principal American carrier base in the western Pacific. However, the surrender order was received just before the attacks were launched, and the submarines were surrendered to the Americans while en route to Japan.

Only many decades later was it revealed that the Seiran had been painted in American colors for their final suicide attack. The aircraft were all ditched at sea before the Americans intercepted the submarines to avoid possible charges of violating the laws and customs of war.


Francillon (1979)

Sakaida et al. (2006)

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