Lockheed XP-49 Lightning
Produced in competition with Grumman's land-based XP-50
version of the Skyrocket, the XP-49 was "Kelly" Johnson's to develop a
much more powerful version of the P-38,
itself a very "hot" ship. The
key to this extra capability was to be the substitution pf Pratt &
Whitney X-1800 engines in place of the Lightning's V-1710s. The X-1800
would have produced up to 2,200hp but development stalled after a
single test engine had been built. This led to the use of Continental
XI-1340s instead.
USAF photo
XP-49 flight testing began in November, 1942 but the Continental
engines did not give the new aircraft enough of a performance advantage
to merit disrupting the established P-38 production effort.