In May 1941, the production
lines at Curtiss were busy with a new P-40 model--the P-40D
The P-40D introduced a new engine,
the Allison V-1710-39 of 1150 hp. This engine had originally
been proposed for the experimental XP-46 fighter, but the USAAC
had decided not to interrupt the P-40 production lines for a
new type and decided instead to adapt the new engine to the
existing P-40. Substitution of the modified P-40 for the experimental
P-46 was proposed on June 10, 1940, and Curtiss agreed to adapt
the basic P-40 to the new engine. The designation P-40D was
assigned to the new project. The P-40D was considered sufficiently
different from previous P-40 versions that it was allocated
a new company designation by Curtiss--Model 87.
The P-40D introduced a new shorter
nose design that was retained by all subsequent P-40s. The 1150
hp V-1710-39 engine had spur gear reduction that raised the
thrust line by six inches, giving a completely different nose
geometry. The overall length was reduced by six inches, the
cross section of the fuselage was reduced, and the undercarriage
was shortened. The radiator was increased in size and moved
forward. Some 175 pounds of armor were added. The fuselage guns
were deleted, and two 0.50-inch machine guns with new hydraulic
chargers were installed in each wing. There were additional
provisions in the wings for two 20-mm cannon, but these were
never actually used. Shackles were added under the belly to
accommodate a 51-gallon auxiliary fuel tank or a 500-pound bomb.
Wing rack attachment points were provided for six 20-pound bombs.
Gross weight of the D model was increased to 8670 pounds. The
climb rate and ceiling consequently continued to remain poor.
Even before the first P-40D
had been built, the United Kingdom ordered 560 examples for
the RAF in May of 1940. The airframe and engine changes justified
a new name--Kittyhawk I. An unspecified number of Model 87s
had also been ordered by France, but were never delivered. They
were designated Model 87-A1 by the company, but this designation
was cancelled after France fell. The following is a list of
RAF serials for the Kittyhawk I:
AK571/AK870 c/n 14952/55251
AK871/AK950 c/n 15342/15421
AK951/AK999 c/n 18695/18743
AL100/AL230 c/n 18744/18874
Bruce Robertson says that 24
of these were diverted to the Royal Canadian Air Force. However,
Bowers lists Canadian serials 1028/1099 as being assigned to
these Kittyhawks, which comprises 72 aircraft. AK601, AK636,
AK680, AK726,AK778, AK882, AK931, AK939, AK960, AK971, AK992,
AK995, AL102, AL178, AL186, AL188, and AL203 were diverted to
The USAAF did not actually order
the P-40D into production until September of 1940, nearly 5
months after the RAF had ordered the equivalent Kittyhawk I.
The US Army serials were 40-359/381 (c/ns 13234/13256).
War Planes of the Second World
War, Fighters, Volume Four, William Green, Doubleday, 1964.
The American Fighter, Enzo Anguluci
and Peter Bowers, Orion Books, 1987.
United States Military Aircraft
since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian
Institution Press, 1989.
Curtiss Aircraft, 1907-1947,
Peter M. Bowers, Naval Institute Press, 1979.
The Curtiss P-40 Tomahawk, Ray
Wagner, Aircraft in Profile, Volume 2, Doubleday, 1965.
ritish Military Aircraft Serials
1912-1969, Bruce Robertson, Ian Allen, 1969