Copyright 2007 by Brandon Cope
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Aichi M6A Seiran
The M6A was undoubtedly the best plane ever carried aboard a submarine.
Specifically designed for the STo (I-400) class submersible carriers,
the M6A was a well-streamlined design with good performance and payload
(a 1,760-lb torpedo or a similar weight of bombs). Despite claims to
the contrary, the floats could not be jettisoned in flight for kamikaze
missions. There are also claims that the planes were not supposed to be
recovered, but were to be ditched instead. However, since the floats
weren’t necessary for launch and the submarine had a crane to recover a
floatplane in the water, this is a dubious claim. Only 20 M6A2’s were
built starting in late 1944 and none saw combat. As the Seiran
(“Mountain Haze”) appeared in small numbers so late in the war, it
never received an Allied code name.
The M6A2 had a crew of two: pilot (who dropped any bombs or torpedo)
and observer/gunner (who manned the Type 2 HMG). The M6A2 uses 47
gallons of aviation gas at routine usage.
Subassemblies: Waterproofed Light Fighter-Bomber chassis with
good streamlining +3, Medium Fighter
Wings with STOL and Folding options +3, 2¥sealed Medium AFV
pontoons +2, two skids +1
P&P: 1,044-kW aerial HP gas engines with 1,044-kW prop and
312-gallon
standard tanks [Body]
Occ: 2 CS Cargo: 2 Body
| Armor |
F |
R/L |
B |
T |
U |
| All |
2/2 |
2/2 |
2/2 |
2/2 |
2/2 |
Armament
Medium Aircraft HMG/13mm Type 2 [Body:B] (500 rounds)
1,760-lb torpedo [Body:U]
Equipment
Body: Long range radio transmitter and receiver, navigation
instruments, autopilot, 1,760-lb hardpoint. Wings: 2¥551-lb
hardpoints.
Statistics
| Size: 30'x40'x15' |
Payload: 1.33 tons |
Lwt: 4.9 tons |
Volume: 156
|
Maint.: 56 hours |
Price: $12,600 |
<>HT: 9.
HPs: 165 Body, 105 each Wing, 200 each Pontoon, 23 each Skid.
| aSpeed: 295 |
aAccel: 6
|
aDecel: 15 |
aMR: 3.75 |
aSR: 2 |
|
| Stall: 69 mph |
|
|
|
|
|
| wSpeed: 28 |
wAccel: 7
|
wDecel: 10 |
wMR: 0.1 |
wSR: 2 |
Draft: 1.4' |
Design Notes
The historical wing area of 291 sf has been used. Design speed was 324
mph. Design flotation rating was 3.7 tons. Performance numbers do not
include loaded hardpoints.
The weight (and cost and HPs) of the pontoons were divided by two to
better match historical weight. Even with that, design weight had to be
reduced by 8% to match maximum takeoff weight (maximum weight assumes a
carried torpedo or approximately 1,800 lbs of bombs).
The floats (and, indeed, the pylons that attached the to the wings)
were detachable. The floats and pylons were not attached until the
plane was moved out of the hangar on the submarine, shortly before
launch. Officially, the I-400 could launch all three of it’s M6A2’s
within 15 minutes of surfacing.
The Seiran requires a 14 mph headwind in order to take off from water.
However, since it was intended to be catapult launched from submarines,
this is not a significant problem.
The skids are located on the underside of the floats.
Variants
The six M6A1 (1943) used a different engine of similar power.
Two M6A2-K trainers (1945) were built, using fixed wheeled landing gear
rather than pontoons.
Had the war gone differently for Japan, additional variations might
have appeared. One possible variant would add two
Ho-103’s (Medium Aircraft HMG) in the nose with 300 rounds per gun, to
serve as flak suppression when attacking.