Mystery Aircraft

Yokosuka Keisei

From Aircraft in Profile Volume 13:

The problems being encountered with the D4Y development also contributed to the decision to abandon another interesting project. In mid-1942 it had been proposed that a modified D4Y1--to be named Keisei--should be built as a special assault aircraft to be used aboard the 18 giant I-400 class submarines then under construction. Instead, the decision was then taken to design and construct a completely new aircraft for this purpose, and in consequence the Aichi M6A Seiran (Mountain Haze) bearing considerably more than a superficial resemblance to the D4Y Suisei in appearance, dimensions and performance, came into being.

From Monogram Close-Up 13:

The original basis for the design [of the M6A Seiran] evolved around the advanced carrier-based dive bomber D4Y1 Suisei (Judy) which had just started rolling off Aichi's Eitoku plant in southwestern Nagoya City that spring [1942]. The hope was that the Suisei, with some modifications, could be adapted for submarine use. In this capacity it was to be named Keisei. The conversion was found to be impractical, however, as was the attempt to have interchangeability of major assemblies between the two aircraft.
Although features of Judy were carried into the basic design of Seiran, a near total redesign became necessary in order to perfect a foldable airplane to fit into the eleven- foot six-inch diameter hangar tube of a submarine. This requirement became the point of departure of the design.

Does anyone have any more information about this aircraft? Presumably it would have been designated Navy Special Attack Bomber Keisei.

Twin-engined Curtiss P-40C

Twin-engine P-40C
Twin-engined Curtiss P-40C

From Domenico sgarlato:

...I received from a friend a picture of an odd-looking Curtis-Wright aircraft, labelled as a twin-engined P-40C; the guy sent me the pic was unable to trace any further information about it. I researched about the idea of a twin-engined P-40 for about 20 years, without any result. Do you know something about it?

24 April 2006
From Stéphane Beaumort:

I've read your request about the twin-engined P-40C mystery, and this is what Peter M. Bowers had to say about it in his Putnam book "Curtiss Aircraft 1907-1947": "Twin-engined P-40-In 1942, P-40C 41-13456 was modified to become the mock-up of an undesignated twin-engined fighter. Packard-Merlin engines and nose cowling from P-40Fs or Kittyhawk IIs were adapted to nacelles fitted to the top of the P-40C wing. No further information is available."

Joe Baugher lists P-40C s/n 41-13456 as being "condemned Feb 27, 1943."

UPDATE 3 April 2011
From Alan Griffith:

A bit of a correction on the information on your site.

The "Twin P-40" is an even greater mystery than is suggested by the emails you've received. Although the serial number on the tail of this aircraft is that of a P-40C, a close examination of the airframe shows it is that of the P-40D/E on in terms of structure. All this really does is add more questions, not less. What happened to the P-40C to which the serial number was assisgned? Is the fuselage an actual fuselage or a mockup along with the rest of the aircraft? And finally, what madman came up with an idea like this? On the basis of visibility alone it would have been like flying a box with no windows. Hardly fighter material.

I hope this helps to confuse the issue even further!


  1. Mikesh, Robert C. Monogram Close-Up 13: Aichi M6A1 Seiran: Japan's Submarine-Launched Panama Canal Bomber. Monogram Aviation Publications, Boylston, Massachusetts, 1975. ISBN 0-914144-13-8.
  2. Richards, M. C. and Donald S. Smith. "Aichi D3A ('Val') & Yokosuka D4Y ('Judy') Carrier Bombers of the IJNAF." Aircraft in Profile Volume 13. Ed. Charles W. Cain. Doubleday & Company, Inc., New York, 1974. ISBN 0-385-096712.
  3. Domenico sgarlato:
  4. Stéphane Beaumort:
  5. Alan Griffith:

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© 1997-2013, Robert Beechy
Originally posted 4 December 2005
Modified: 02/03/2013