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Curtiss P-40 (Part 3)

By Joseph Baugher

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. 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 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 place.

Even though in 1943 the Warhawk was rapidly becoming obsolescent, the P-40N became the version that was most widely built--5220 examples rolling of the production lines.

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. 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, 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.

The P-40N-15-CU production block aircraft differed in having the battery located forward of the firewall and new landing lights.

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 only in having a revised instrument panel. 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. They were similar to the N-25 except for valve and electrical system changes. The N-30 had modifications to the lubrication system. 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.

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, 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 13,738th P-40 built.

One P-40N was experimentally fitted with a bubble canopy and was unofficially designated XP-40N.

The following spec refers to the P-40N-15-CU:

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 feet.

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.

586 P-4ONs were to be Kittyhawk IVs for 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) FT849/954 FX498/847

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:

P-40N-1-CU A29-415/419

A29-435/442

A29-461/472

A29-503/541

A29-559/563

A29-577/587

P-40N-5-CU A29-542/558

A29-564/576

P-40N-20-CU A29-600/704

P-40N-25-CU A29-800/811

A29-819/828

P-40N-30-CU A29-900/928

P-40N-35-CU A29-1000/1079

P-40N-40-CU A29-1100/1221

These Kittyhawk IVs were primarily operated in the South-West Pacific campaigns as low-altitude fighter and ground attack aircraft. Thew 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:

NZ3120/3179

NZ3182/3270

NZ3272/3293

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

42-104829/105928 Curtiss P-40N-5-CU Warhawk

42-105929/106028 Curtiss P-40N-10-CU Warhawk

42-106029/106405 Curtiss P-40N-15-CU Warhawk

42-106406/106428 Curtiss P-40N-20-CU Warhawk

43-22752/24251 Curtiss P-40N-20-CU Warhawk

43-24252/24751 Curtiss P-40N-25-CU Warhawk

44-7001/7500 Curtiss P-40N-30-CU Warhawk

44-7501/8000 Curtiss P-40N-35-CU Warhawk

44-47749/47968 Curtiss P-40N-40-CU Warhawk

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.

There is a P-40N on display in the Champlin Fighter Museum at Mesa, Arizona. I am unaware of its serial number. It is painted in Chinese Flying Tiger colors.

The P-40Q was an experimental project which attempted to produce a really modern fighter out of the existing P-40. The modifications were in fact so drastic that there was very little in common with earlier P-40 versions. Two P-40Ks (serial numbers 42-9987 and 42-45722) and one P-40N (serial number 43-24571) were extensively modified with revised cooling systems, two-stage superchargers, and structural changes which markedly altered their appearance. The project was assigned the designation XP-40Q.

The first XP-40Q was P-40K-10-CU ser no 42-9987 fitted with a new cooling system, a longer nose, and a four-bladed propeller. The radiators were moved into an under-fuselage position, with intakes between the undercarriage legs.

The most prominent XP-40Q feature, used on 42-45722 and 43-24571, was the cutting down of the rear fuselage and the addition of a bubble canopy as on the "XP-40N". Later the wingtips were clipped. The result was an aircraft which bore almost no resemblance whatsoever to its parent P-40 line. The V-1710-121 engine was fitted with water injection, resulting in a power of 1425 hp. Speed increased to 422 mph at 20,500 feet, making it the fastest of all the P-40s. An altitude of 20,000 feet could be reached in 4.8 minutes, and service ceiling was 39,000 feet. Four 0.5-inch machine guns were carried by the prototypes. Wingspan was 35 feet 3 inches (after clipping), and length was 35 feet 4 inches (2 feet longer than the P-40N).

The proposed production models of the P-40Q were to have carried either six 0.50-inch machine guns or four 20-mm cannon, but the XP-40Q was still inferior to contemporary production Mustangs and Thunderbolts, and development was therefore abandoned. Consequently, the production life of the P-40 ended with the N version.

The second XP-40Q was briefly used for postwar air racing. Registered NX300B, the second XP-40Q was an unauthorized starter in the 1947 Thompson Trophy race. It was in fourth place when it caught fire and had to drop out of the race.

Sources:

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.

Joe Baugher

AT&T Bell Laboratories

2000 North Naperville Road

Naperville, Illinois 60566-7033