Warhawk, Kittyhawk IV
By the summer of 1943, the performance
of the P-40 Warhawk was leaving much to be desired, especially
in comparison to the later types such as the P-38, P-47, and
P-51 which were beginning to come into service. The P-40N version
(company designation Model 87V, 87W) was introduced at this
time in an effort to improve the capabilities of the basic design
and thus avoid interrupting Curtiss production lines by having
the company introduce an entirely new type. The first 1500 examples
of this new Warhawk line were to have been delivered as P-40Ps
powered by Merlin engines, but shortages of the Packard-built
Merlin caused this order to be cancelled and the P-40N with
the 1200 hp Allison V-1710-81 engine to be substituted in its
A new lightweight structure
was introduced, two of the six wing-mounted guns were removed,
smaller and lighter undercarriage wheels were installed, head
armor was reintroduced, and aluminum radiators and oil coolers
were installed. The resulting reduction in the weight, along
with the use of the same V-1710-81 engine as used in the P-40M,
made the P-40N the fastest of the P-40 series, reaching a speed
of 378 mph at 10,500 feet. Even though by 1943 standards the
Warhawk was rapidly becoming obsolescent, the P-40N became the
version that was most widely built--5220 examples rolling off
the Curtiss lines before production finally ceased.
There were several production
blocks of the P-40N, which differed from each other as follows:
The first production block was
the P-40N-1-CU. It appeared in March of 1943, still powered
by the Allison V-1710-81 engine, but with 122 gallons of internal
fuel and a generally lighter structure than its predecessors.
With weight reduced to 6000 pounds empty, 7400 pounds gross,
and 8850 pounds maximum, the N-1 was the fastest P-40 service
variant and was intended for high altitude combat. Maximum speed
was 378 mph at 10,500 feet and service ceiling was 38,000 feet.
An altitude of 15,000 feet could be attained in 6.7 minutes.
Armament consisted of four 0.50-inch machine guns in the wings.
Four hundred P-40N-1-CUs were built.
The P-40N-5-CU variant introduced
a modified cockpit canopy with a frameless sliding hood and
a deeper, squared-off rectangular aft transparent section to
improve the rearward view. This cockpit canopy was retained
for all the rest of the production blocks of the N version.
The N-5 version restored the full six-gun wing armament, since
pilots had complained that four guns were insufficient. Underwing
racks were fitted for bombs or drop tanks, increasing external
stores capacity to 1500 pounds. The new heavier gross weight
of 8350 pounds limited top speed to 350 mph at 16,400 feet and
service ceiling to 31,000 feet. An altitude of 14,000 feet could
be attained in 7.3 minutes. Range was 340 miles with a 500-pound
bomb underneath the fuselage. Three drop tanks promised a ferry
range of up to 3100 miles at 198 mph.
The P-40N-6-CU was the designation
given to N-5s modified in the field and fitted with reconnaissance
cameras in the fuselage.
The P-40N-10-CU production block
aircraft were winterized aircraft. It had a faster climb rate,
made possible by the removal of two wing guns.
The P-40N-15-CU production block
aircraft differed in having the battery located forward of the
firewall and new landing lights. The full six wing guns were
installed, and larger capacity wing tanks were fitted.
The P-40N-20-CU introduced the
V-1710-99 engine, which was simply an -81 powerplant with an
automatic engine control unit.
The P-40N-25-CU differed from
the N-20 only in having a revised instrument panel and in having
non-metal self sealing fuel tanks.
The P-40N-26-CU was the designation
given to N-5s fitted with reconnaissance cameras in the fuselage.
Three P-40N-25-CUs were converted
as two-seat trainers under the designation RP-40N-26-CU.
On February 14, 1944, another
thousand Warhawks were ordered, broken down into a batch of
500 N-30s and 500 N-35s.
The N-30 was similar to the
N-25 except for valve and electrical system changes.
Twenty-two N-30s were converted
to two-seat trainers as P-40N-31-CU. Seventy were converted
to P-40R-1 trainers in 1944.
The P-40N-35-CU featured changes
in the carburetor, the instruments, and the lighting. . The
N-35 had modifications to the lubrication system, and featured
updated electrical systems, and a new radio and ADF equipment.
As late as June 30, 1944, when
the front-line equipment of all major air forces had far outpaced
the potential of the P-40 series, an order for yet ANOTHER 1000
Warhawks was placed. This was the P-40N-40-CU production block.
However, this order was later cut back to 220 aircraft. The
N-40 was powered by the V-1710-115 engine of 1360 hp and featured
metal-covered ailerons. The N-40 variant dispensed with the
camouflage finish starting with 44-47860. It included improved
non-metallic self-sealing fuel tanks, automatic propeller control,
new radio and oxygen equipment, and flame-damping exhausts.
The last production Warhawk
was a P-40N-40-CU which left the assembly line on November 30,
1944, being the 13,739th P-40 built.
One P-40N was experimentally
fitted with a bubble canopy and was unofficially designated
The following spec refers to
One 1200 hp Allison V-1710-81
twelve-cylinder liquid-cooled engine. Maximum speed 208 mph
at 5000 feet, 325 mph at 10,000 feet, 343 mph at 15,000 feet.
Maximum climb rate was 2120 feet per minute at 5000 feet, 2230
feet per minute at 10,000 feet. An altitude of 10,00 feet could
be attained in 4.7 minutes, 20,000 feet in 8.8 minutes. Service
ceiling was 31,000 feet. Range was 750 miles at 10,000 feet
(clean). With one 62.4 Imp gal drop tank, range was 1080 miles.
Weights were 6200 pounds empty, 8350 pounds loaded, 11,400 pounds
maximum. Dimensions were wingspan 37 feet 4 inches, length 33
feet 4 inches, height 10 feet 7 inches, wing area 236 square
Many of the P-40Ns were shipped
to Allied air forces under Lend-Lease, and comprised the majority
of the 1097 P-40s sent to the USSR. Most of their operational
flying took place in the Pacific in fighter-bomber or escort
roles, most of them flown by RAF, RAAF, and RNZAF pilots. In
USAAF service, the P-40N was relegated largely to training roles,
as later types such as the P-51 Mustang or the P-47 Thunderbolt
became increasingly available in quantity.
The P-40N was known as Kittyhawk
IV in RAF service. 586 P-4ONs were to be delivered to Britain,
but the first 130 were diverted to the USSR. The RAF Kittyhawk
IV serials were as follows:
FS270/399 (all diverted to the USSR)
Although the RAF evaluated the
P-40Ns in the United Kingdom, they were employed solely abroad.
Most of the RAF Kittyhawk IVs were phased out of service early
in 1945, but one RAF squadron continued to operate the Kittyhawk
IV until the end of hostilities. RAF squadrons equipped with
the P-40N included Nos 112, 250, and 450.
468 P-40Ns were sent to Australia.
There serials were as follows:
These Kittyhawk IVs were primarily
operated in the South-West Pacific campaigns as low-altitude
fighter and ground attack aircraft. They were progressively
replaced by Mustangs and Spitfires during the last year of the
war, but the Kittyhawks continued to serve with RAAF Squadrons
75, 78, and 80 until the end of hostilities.
172 P-40Ns were supplied to
New Zealand. Their serials were as follows:
35 P-40Ns were supplied to Canada.
Their serials were 846/880.
41 P-40Ns were supplied to Brazil,
where some served until 1958. They were serialled in 1945 in
the range 4020/4100. One of them still survives there as a monument
(USAAF serial 44-7700, Brazilian serial 4064).
An unspecified number were delivered
to the Royal Netherlands East Indies Air Corps. They flew them
against the Japanese in the latter stages of the war, then against
the nationalist rebels in Indonesia until February of 1949.
A large proportion of the 2097
P-40s supplied to the Soviet Union were of the P-40N variety,
but they were not very popular with the Russians, who considered
them incapable of absorbing as much battle damage as the P-39
Airacobra. The USAAF serials of the P-40N production blocks
were as follows:
42-104429/104828 Curtiss P-40N-1-CU Warhawk c/n 38191/28590
42-104829/105928 Curtiss P-40N-5-CU Warhawk c/n 28591/29690
42-105929/106028 Curtiss P-40N-10-CU Warhawk c/n 29691/29790
42-106029/106405 Curtiss P-40N-15-CU Warhawk c/n 29791/30167
42-106406/106428 Curtiss P-40N-20-CU Warhawk c/n 30168/30190
43-22752/24251 Curtiss P-40N-20-CU Warhawk c/n 30691/32190
43-24252/24751 Curtiss P-40N-25-CU Warhawk c/n 32191/32690
44-7001/7500 Curtiss P-40N-30-CU Warhawk c/n 32741/33240
44-7501/8000 Curtiss P-40N-35-CU Warhawk c/n 33241/33740
44-47749/47968 Curtiss P-40N-40-CU Warhawk c/n 33741/33960
44-47969/48748 Curtiss P-40N-40-CU Warhawk contract cancelled.
Those few P-40Ns still in service
in 1948 with the USAAF were redesignated ZF-40N.
War Planes of the Second World
War, Fighters, Volume Four, William Green, Doubleday, 1964.
The American Fighter, Enzo Angelucci and Peter Bowers, Orion
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
The Curtiss P-40 Tomahawk, Ray Wagner, Aircraft in Profile,
Volume 2, Doubleday, 1965
Hawk Dynasty: The Curtiss Hawk Monoplanes, Ken Wixey, Air Enthusiast
No 72 (1997).