Curtiss built 15,000 fighter aircraft for WWII and the P-40's made up a substantial number of these.

Although not an outstanding fighter, the P-40 was well respected as a sturdy and reliable fighting platform which saw a great deal of service in China.

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Curtiss P-40 (Part 2)

By Joseph Baugher

In 1941, P-40D Ser No 40-360 was fitted with a 1300 hp British-built Rolls-Royce Merlin 28 engine with a single-stage two-speed supercharger. It flew for the first time on June 30, 1941. This experimental P-40D could be distinguished from the P-40E by the absence of the top-mounted carburetor air scoop. The Merlin engine did much to overcome the limitations imposed by the Allison, and a total of 1311 Merlin-powered examples were ordered under the designation P-40F.

The P-40F and later versions were known by the name *Warhawk* in US service. In British and Commonwealth service, they were known as *Kittyhawk*.

The first 699 planes of the P-40F series had no dash numbers. The P-40F-5-CU and later models had their fuselages elongated from 31 feet 2 inches to 33 feet 4 inches in order to improve directional stability. The P-40F-10-CUs had manual instead of electric cowl flap controls. The P-40F-15-CUs had winterizing equipment, and the P-40F-20-CUs had a revised oxygen flow system for the pilot.

The P-40F was powered by a Packard-built Merlin V-1650-1 twelve-cylinder Vee liquid-cooled engine rated at 1300 hp for takeoff and 1120 hp at 18,500 feet. Maximum speed was 320 mph at 5000 feet, 340 mph at 10,000 feet, 352 mph at 15,000 feet, and 364 mph at 10,000 feet. An altitude of 10,000 feet could be attained in 4.5 minutes, and an altitude of 20,000 feet could be reached in 11.6 minutes. Maximum range was 700 miles at 20,000 feet (clean), 875 miles (one 43 Imp gal drop tank), and 1500 miles (141.5 Imp gal drop tank). Service ceiling was 34,400 feet. Weights were 6590 pounds empty, 8500 pounds normal loaded, and 9350 pounds maximum. Dimensions were 37 feet 4 inches wingspan, 33 feet 4 inches length (P-40F-5-CU and later), 10 feet 7 inches high, 236 square feet wing area.

One hundred and fifty P-40Fs were supplied to the RAF under Lend-Lease. The RAF assigned them the name Kittyhawk II. The Kittyhawk IIs were offset from USAAF allocations 41-13697/14599. RAF serials were FL219/448. Unfortunately, P-40Ls were also mixed in with this lot with no mark distinctions, so it is impossible to tell which planes were Fs and which were Ls by merely looking at the RAF serial number. In the event, very few of these aircraft actually served with the RAF. FL273 and FL369-448 were returned to the USAAF for use in North Africa in 1942/43. FL230/232, 235,236, 239/240 were lost at sea before reaching the RAF. FL263,270,276,280,383,305,and 307 were handed over to the Free French, who operated them in North Africa. 100 were transferred to the USSR.

The designation YP-40F was unofficially assigned to P-40F Ser No 41-13602 used for experimental tests of the cooling system and the tail rudder. The coolant system was moved aft in several different configurations, including inside a thickened wing-root section.

USAAF serials of the P-40F were as follows:

41-13600/13695 Curtiss P-40F Warhawk

41-13696 Curtiss P-40F Warhawk (order cancelled)

41-13697/14299 Curtiss P-40F Warhawk

41-14300/14422 Curtiss P-40F-5-CU Warhawk

41-14423/14599 Curtiss P-40F-10-CU Warhawk

41-19733/19932 Curtiss P-40F-15-CU Warhawk

41-19933/20044 Curtiss P-40F-20-CU Warhawk

A number of P-40Fs were selected at random and withdrawn from operational service and relegated to training duties and fitted with Allison V-1710-81 engines in place of their original Merlins. These were redesignated P-40R-1. At least 70 such conversions have been recorded.

The designation P-40G was given to 44 existing P-40s that were fitted

with H81-A2 Tomahawk IIa wings that carried four 0.30-inch machine

guns. These retrofits took place between August and September 1941.

Company records refer to these conversions under the designation Model

81-AG. Serials of P-40s retrofitted were as follows:

39-162,176,181,187,190,191,196,197,204,206,209,217,220,221,226,235,238,248,257,263,267,275,276,279,288 and 40-292,297,299/301,303,309,315,318,320,323,331/333,335/338.

For some reason, P-40 Ser no 39-221 was unofficially designated XP-40G (company Model 81-AG).

Some sources have at least some of these P-40Gs being assigned new Army serial numbers after these modifications were completed. These new serial numbers included:

42-14261/14274 Curtiss P-40G Warhawk

42-14277/14278 Curtiss P-40G Warhawk

42-14281 Curtiss P-40G Warhawk

However, these numbers conflict with those assigned to an order for P-40L-30-CUs which was cancelled.

Sixteen of these P-40Gs were shipped to the USSR starting in October 1941. All those examples remaining in the USA were redesignated RP-40G in October 1942, where the R meant "restricted from combat use".

39-221 was shipped to the USSR in 1943.

For some reason, the designation P-40H was never assigned. The designation P-40I was never assigned in any case, lest the letter "I" be confused with the number one.

The designation P-40J was given to a projected version of the P-40E which was to have a turbosupercharged engine. This study was abandoned in May 1942 without anything ever being built.

Despite the success of the Merlin engine in the Warhawk, parallel production of the Allison-powered version continued owing to the limited supplies of the license-built British engine. The P-40K series marked the introduction of the more powerful Allison V-1710-73 (F4R) engine rated at 1325 hp for takeoff and 1150 hp at 11,800 feet. On October 28, 1941, 600 P-40Ks were ordered for Lend-Lease supply to China. It was envisaged that this would be the last P-40 model to be built in quantity, the P-60 replacing the P-40 on the Curtiss production lines thereafter. However, delays in the P-60 program caused the order for P-40Ks to be increased to a total of 1300 aircraft on June 15, 1942.

The first P-40K model rolled off the production line in August 1942. For some odd reason, the company model number used for the P-40K is unknown.

The P-40K-1-CU and P-40K-5-CU were generally similar to late-production P-40Es except for the more powerful engine with an auto manifold pressure regulator. The K-5 added rotary valve cooling. The K-1 and K-5 retained the short fuselage of the P-40E, but with the extra power there was a tendency to swing during takeoff and a dorsal fin was added to correct this problem. The P-40K-10s and later production blocks had the longer fuselage introduced on the P-40F-5-CU. The P-40K-15-CU was winterized.

The maximum speed of the P-40K was 320 mph at 5000 feet and 362 mph at 15,000 feet. A climb to 15,000 feet took 7.5 minutes. Range was 350 miles with a 500-pound bomb attached. Ferry range was 1600 miles. Weights were 6400 pounds empty, 8400 pounds gross, and 10,000 pounds maximum.

Most of the P-40Ks served with the US forces in Asia and the Pacific and under Lend-Lease with the Chinese Air Force. 192 P-40K-1-CUs were diverted to England under Lend-Lease as Kittyhawk III. RAF serials were FL875/905, FR111/115, FR210/361, and FL710/713. Forty-two P-40Ks served with the RAAF under serials A-29-164/202 (P-40K-10-CU) and A-29-203/205 (P-40K-15-CU). P-40Ks servicing with the RNZAF were NZ3045/3065, NZ3090, and NZ3099. Nine P-40K-1-CUs served with the RCAF under US Army serial numbers 42-45921, 45944, 45945, 45951, 45952, 45954, 45977, 46003, and 46004.

The serials for the P-40Ks were as follows:

42-9730/9929 Curtiss P-40K-5-CU Warhawk

42-9930/10264 Curtiss P-40K-10-CU Warhawk

42-10265/10429 Curtiss P-40K-15-CU Warhawk

42-45722/46321 Curtiss P-40K-1-CU Warhawk

The P-40K-1 had originally been assigned serials 42-65902/66501. The P-40K-5 thru -15 were originally assigned serials 42-64502/65201. These were all cancelled and reassigned as shown above.

One P-40K-10-CU, 42-10219, was fitted with an Allison V-1710-43 and used to develop P-40 improvements under the designation XP-40K. Experiments with cowling and relocated cooling systems altered the appearance from time to time. One such modification produced an aircraft with radiators in a swollen wing center section and a slim, pointed nose.

In order to improve the Warhawk's performance in short-range combat, the P-40L version was created. It was basically a "stripped" version of the Merlin-powered P-40F-5-CU, in which 250 pounds of weight was saved by the partial removal of fuel, armament, and other equipment. The P-40L (Model 87-B3) was otherwise virtually identical to the Merlin-powered P-40F-5-CU. Some of the P-40L production blocks featured planes with reduced armament and smaller capacity fuel tanks in order to obtain reduced weight and better performance. The L-model was sometimes known as the "Gipsy Rose Lee", after the famous strip-tease dancer of the time.

The P-40L-1-CU had the same fuel and armament as the P-40F.

The P-40L-5-CU and and subsequent P-40Ls had two wing guns removed to reduce the total armament to four 0.50-inch machine guns with 201 rounds per gun. Internal fuel was reduced by 31 Imp gal.

The P-40L-10-CU had electrical aileron trim tabs and engine control changes.

The P-40L-15-CU had revised carburetor air filters and inter-aircraft signal lights.

The P-40L-20-CU had radio and electrical changes and provisions for an incendiary (destruct) grenade.

Despite the weight savings, the maximum speed of the P-40L was a mere 4 mph greater than that of the P-40F at rated altitude.

One hundred P-40Ls were sent to Britain as Kittyhawk IIs with no mark distinctions from the P-40Fs. The RAF serials for the P-40Ls were FS400/499. 160 other P-40Ls reached the RAF as Kittyhawk IIIs. Their serials were FL714/730, FR116/140, FR385/392, and FR413/521.

The P-40Ls were originally assigned the serial numbers 42-65202/65901. These numbers were cancelled and were replaced as follows:

42-10430/10479 Curtiss P-40L-1-CU Warhawk

42-10480/10699 Curtiss P-40L-5-CU Warhawk

42-10700/10847 Curtiss P-40L-10-CU Warhawk

42-10848/10959 Curtiss P-40L-15-CU Warhawk

42-10960/11129 Curtiss P-40L-20-CU Warhawk

42-11130/11676 Curtiss P-40L-25-CU Warhawk - contract cancelled

42-14237/14296 Curtiss P-40L-30-CU Warhawk -- contract cancelled.

A certain number of P-40Ls were selected at random and were withdrawn from operational service and modified with the adoption of the 1360 hp Allison V-1710-81 engine in place of the original Merlin. They were used as advanced trainers. They were redesignated P-40R-2. At least 53 P-40L-->P-40R conversions took place which can be identified by serial number, but there were probably many more.

In 1943, the scarcity of Packard Merlin engines necessitated that the Allison engine be reintroduced into the P-40 production line. The result was the P-40M version. The P-40M was essentially similar to the P-40K-20-CU, apart from the use of the Allison V-1710-18 engine rated at 1200 hp for takeoff and 1125 hp at 17,300 feet. The P-40M could be distinguished by the introduction of a cooling grill forward of the exhaust stubs.

The P-40M was built solely for Lend-Lease, the contract being approved on August 24, 1942. The first P-40M appeared in November, 1942. Most of them went to the RAF, the RAAF, and the RNZAF as the Kittyhawk III. The type served with British Commonwealth forces in the Far East. A number were operated in Italy by No. 5 Squadron of the South African Air Force.

The differences between the production blocks were as follows:

The P-40M-1-CU had reinforced ailerons.

The P-40M-5-CU had improved carburetor air filters and further aileron improvements.

The P-40M-10-CU had revised undercarriage warning systems and fuel system changes

Serials of the P-40M were as follows:

43-5403/5462 Curtiss P-40M-1-CU Warhawk

43-5463/5722 Curtiss P-40M-5-CU Warhawk

43-5723/6002 Curtiss P-40M-10-CU Warhawk

The RAF serials for the 264 P-40Ms supplied to the RAF as Kittyhawk IIIs were FR779/872 and FS100/269. 168 P-40Ms were supplied to Australia as Kittyhawk IIIs under the serial numbers A29-300/389, A29-400/414, A29-420/434, A29-442/460, and A29-473/502. 34 P-40Ms went to New Zealand as serial numbers NZ3066/3073, NZ3075/3089, NZ3109/3119, and NZ3180. The P-40M equipped the No. 5 Squadron of the South African Air Force serving in Italy. 19 P-40Ms were transferred to Brazil.