Which significant WWII combat aircraft where designed after the war started?

[Karnak]

How many, and which, significant WWII combat aircraft began their design process after the war started and were designed based on combat experience?  Not upgrades of older airframes, but entirely new designs.

F4U?
Ki-84?
B-29?
Me262?
Mosquito?

[Bosco123]

B-29 I would say. It was the B-36 and now the B-52.

[Anaxogoras]

Spanish civil war count?

[Saxman]

F4U began development before the war started, although lessons learned in the BoB were applied to her design (particularly armament).

[Stoney]

F6F and P-61 I think are the only two for American fighters if you don't count the F7F and F8F.  F4U and P-51 designs started before the war started.

SB2C and A-26 for American attack aircraft?

B-29 for American bombers?

[Karnak]

Spanish civil war count?

No.  I'd count from Sept., '39 for Britain and Germany, June, '41 for the USSR and Dec., 1941 for the US and Japan.

[Cthulhu]

F4U began development before the war started, although lessons learned in the BoB were applied to her design (particularly armament).

Beat me to it. 

 Believe it or not, the same can be said for the F6F. Was on the boards prior to Pearl Harbor, although I'm sure the captured Zero prompted some needed design changes.

[Stoney]

Believe it or not, the same can be said for the F6F. Was on the boards prior to Pearl Harbor

I didn't know that.  I didn't think they started designing it until after the war had started.  Of course, with a first flight in summer of 1942, that would have been a quick turn around.

[Cthulhu]

I didn't know that.  I didn't think they started designing it until after the war had started.  Of course, with a first flight in summer of 1942, that would have been a quick turn around.

Yeah, but frankly given the way aircraft designs go from conceptual to preliminary design, with significant (sometimes major) changes along the way, it could be debatable when something we'd all agree on as being say, an F6F, was actually born. It would be interesting to see how many pertubations Grumman's G-50 went thru before it settled into something we'd recognize as a Hellcat.

[eddiek]

Me262 was on the drawing board before the war started, wasn't it?  I read somewhere the plans were laid out in April of 1939?

[Greebo]

The Mustang was designed in 1940 after its intended user (the RAF) entered the war and using their combat experience.

[Lusche]

Me 163 (though it had some pre-war roots)
He 162

Ju 188/388, (depending if you see them as independend designs or merely advanced Ju 88 variants)

He 219

Ar 234


Transports, not really "combat" aircraft:

Ju 252 and 352 (minor production only, about 60 planes delivered)

Me 323 (and 321)

Ar 232

[steely07]

Not significant, but the CAC Boomerang was designed and built after the outbreak of hostilities.

Development

The Wirraway trainer provided a starting point for the Boomerang's airframe. CAC general manager (and former chief designer) Lawrence Wackett and chief designer Fred David began detailed design work at the CAC factory in Fishermans Bend, Melbourne on 21 December 1941. David was a Jewish refugee from Austria, who had worked on aircraft designs for Heinkel in pre-Nazi Germany, as well as for Mitsubishi and Aichi in Japan.[2][3] As a result, he had a comprehensive knowledge of advanced contemporary fighter designs, including the Heinkel He 112 and A6M Zero.

The RAAF ordered 105 CA-12 (Mark I) Boomerangs on 2 February 1942, before the prototype first flew on 29 May 1942.

[Stoney]

The Mustang was designed in 1940 after its intended user (the RAF) entered the war and using their combat experience.

Good point

[Ack-Ack]

No.  I'd count from Sept., '39 for Britain and Germany, June, '41 for the USSR and Dec., 1941 for the US and Japan.

The war didn't start for Japan in 1941, unless you're not counting their invasion and occupation of China prior to war with the US.


ack-ack