The P-40 Curtiss Kittyhawk

The P-40 Kittyhawk – goes well, downhill.

The aircraft type flown by Nicky Barr in RAAF 3 Squadron had a long and colourful history that commenced with its original contract. Worth $12.9 million in 1939, it was the largest American aircraft manufacturing order since 1918. Competitors cried foul, citing better aircraft and bigger production facilities, all to no avail.

This Curtiss Model 87A, was known variously as the P-40, Hawk-75/81, Warhawk, Tomahawk and Kittyhawk. Others called it the Kittybomber, Gosshawk and even Mohawk. In the RAAF it was the A-29.

Cost $55,000 (US)

The P-40 had an average selling price of only $55,000 (US) and served throughout WW II in every major theatre. Curtiss exported the P-40 in large numbers to 28 nations. It fought notably in the Western Desert, New Guinea, Russia and with the “Flying Tigers” American Volunteer Group in China and Burma.

Minor production modifications and export orders resulted in at least ten version suffixes and more than four nicknames. It was designed as a land-based fighter but employed extensively as a fighter-bomber. Some say there was no P-40A. Others claim the P-40A was either an early version destined for France or a photo-reconnaissance version shipped mainly to Russia. The P-40J version was proposed but never built. A P-40H version seems never to have been either proposed or built. All this was compounded by the very large number of P-40s built between 1939 and 1944 (Angellucci p. 226 says 13,753; Jackson p 99 and the Curtiss Wright website say 13,738). Unfortunately, there are less than perfect records detailing exactly how many of what version were despatched and received where. For instance, it is fairly clear that about 2430 P-40s were built for the Soviet Union but maybe only 2097 arrived (Jackson p. 99).

Allison V12 engine

Curtiss’s Don Berlin developed this P-40 fighter from the mid-1930s vintage Curtiss P-36 Hawk. He simply replaced the Hawk’s radial 1200 hp Pratt and Whitney R-1830-17 Twin Wasp engine with an inline Allison V-1710-33 Vee 12. The new engine produced much the same power, but the P-40 was slightly faster because it had a reduced frontal area.

One perennial problem was that the Allison engine was never quite powerful enough for the heavy P-40 airframe. Curtiss claims this was because the engine had a poor supercharger, which severely restricted its performance, particularly at high altitude.

The late-1930s US practice was to employ an exhaust-driven turbo-supercharger, but these devices required tungsten, a metal that was in short supply. Although other manufacturers in the UK and Germany developed highly successful gear-driven centrifugal superchargers, the Allison version never quite matched their performance. On the other hand, when a turbo-supercharger was fitted to the Allison-engined P-38 Lightning it enabled that heavy fighter to perform brilliantly at high altitude.

The Curtiss-Wright website admits the Allison engine could be tricky:The engine could be a chore to start. The pilot primed the engine using a hand pump on the instrument panel, then depressed a floor pedal with his heel to energize an electric motor, spinning up the inertial starter’s flywheel. After thirty seconds the same pedal, pushed forward, coupled the flywheel to the engine. This procedure rotated the big Allison through one or two turns. If everything was just right, the engine started. Too little or too much prime and the engine would stop; too much prime might start an exhaust manifold fire as well. At any rate the procedure would have to be repeated until the engine started. With the engine running, takeoff had to be expeditious or the cooling system would soon boil over, cancelling the flight.

(Ed. note: the Hurricane and Spitfire also had coolant boiling problems. Pilots learned to cope with these idiosyncrasies.)

The first 140 P-40s, designated Hawk 81-A1 by the manufacturer, were earmarked for the French Armee de l’Air but were diverted to the RAF in September 1940 following France’s capitulation. Called the Tomahawk I by the RAF, these aircraft had French instrumentation, cockpit labelling and even “French-fashion” throttles that operated in a reverse manner. They retained the two 0.5-inch machine guns in the nose, but these were supplemented by four wing-mounted 0.303-inch Browning machine guns in place of the 7.5 mm FN-Brownings originally specified by the French.

The P-40 “Mack truck” could absorb an amazing amount of damage.

Lacking armour protection and self-sealing tanks, the RAF reserved these early Tomahawks mainly for training roles in the UK. Tomahawk IIs (P-40B, C and D), with better armour and other self protection, were active in the Middle East from October 1941 onward.

Curtiss say they optimised the P-40 for low and medium levels. This led to claims that it was marginally better than the Hurricane and even contemporary German Me 109s at low level. As a fighter it could never match the Spitfire at any altitude or the Me109 above 14,000 feet.

Indeed, one German ace in North Africa, Hans-Joachim Marseille (in a Bf109F-4/Trop), claimed no less than 15 P-40s (and two Spitfires) shot down in three sorties on one busy day, 1 September 1941 (The Luftwaffe p. 125).

The Kittyhawk was no match for this Bf109F-4/Trop flown by a capable pilot.

The P-40N of 1943 was the final Kittyhawk version to be constructed in large numbers (Angelucci p 226 says the total was 5219; others claim 5520). This version had a 1360 hp Allison V1710-81 engine and incorporated a number of weight-saving and other modifications. All the later P-40Ns had six 0.5-inch wing-mounted guns, three bomb racks and an optional 52-gallon external centreline fuel tank.

SAAF and RNZAF

Other Commonwealth nations to fly the P-40 included Australia, South Africa and New Zealand. Allison engines powered most P-40s, but a Packard-built 1300 hp Rolls Royce Merlin engine was installed in some machines, most of which seem to have been exported either to Russia or Britain. The Packard-Merlin engine was in short supply because most of that production line was earmarked for the highly successful private venture North American P-51 Mustang. The USN had better fighters, like the Grumman F6F Hellcat and the Vought F4U Corsair, so the P-40 was never fitted with an arrestor hook for carrier work. However, it was not unusual for USAAC P-40s to be ferried to an operational area and flown ashore from an aircraft carrier.

The ability of the Tomahawk/Kittyhawk to absorb an incredible amount of punishment and repeated high G forces became almost legendary, but its carburettor air filter in the desert and its electrical system in the wet tropics presented some problems. Australia used the P-40 as its chief light ground attack aircraft in the Western Desert with Numbers 3 and 450 RAAF Squadrons operating the P-40E (Kittyhawk II A29-1 to A29-163) alongside RAF and South African Air Force P-40s.

RAAF additional purchases

The RAAF acquired another 838 P-40M and P-40N Kittyhawks for the Pacific Theatre, but it was chiefly the P-40E fighter-bombers in RAAF 75 and 76 Squadrons that, for the first time in history, contributed to defeating a 2000-strong Japanese invasion in August-September 1942 at Milne Bay. Flying in atrocious conditions that included low ceilings, heavy rain, mountainous terrain and boggy airfields under direct enemy fire, the rugged RAAF P-40Es performed brilliantly. Sometimes their pilots opened fire on Japanese targets before fully retracting their wheels after takeoff.

RAAF 75 Squadron Kittyhawk pilots B. Watson (left) C. Norman, R. Ridell, B. Hall and Nat Gould return from a Milne Bay sortie.

The P-40 had its limitations as a fighter in the Pacific, particularly against the Japanese Mitsubishi A6M Zero. LCDR Kofukuda, Flight Commander of the Japanese 6th Air Corps at Guadalcanal, accurately recorded at the time that the manoeuvrability of the American P-40 was markedly inferior to the Zero:

While the Tomahawk (sic) possessed the same maximum speed as the (Zero), it lacked the rate of climb of our fighter and could not hope to match it in close combat. The Tomahawk pilots therefore took advantage of their superior diving speed, and almost invariably resorted to ‘shoot and retreat’ tactics. Thus, they usually refused combat unless they possessed the advantage of altitude, which enabled them to dive into the (Zero) formations with blazing guns and race away at a diving speed beyond that possible with a (Zero). (Okumiya and Horikoshi pp 181-82).

Bruce Brown, an ex-75 Squadron pilot, whose beautifully restored P-40 “Polly” sits in the Australian War Memorial, Canberra, agrees:

Well, it was not as manoeuvrable as a Zero or any of the Japanese aircraft. It was not as manoeuvrable as a Spitfire either. It was a much heavier aircraft than a Spitfire (and) a Zero. It was really slightly underpowered in my opinion for its weight! But its one attribute was being so heavy and being so strongly constructed that provided you had height and, say, as an example, 15,000 feet and enemy Zeros got onto your tail, if you pushed everything onto one corner as we used to say, rudder and control column, and headed straight for the deck, you would get away from them because being heavier than they were and going down hill, you’d pick up speed much quicker and consequently you could get away. So, the other attribute was its firepower. It was a beautiful firepower both from the point of view of combat “aerial combat” and also ground support work where you were operating against the enemy with the army (www.ww2australia.gov.au).

Another seven RAAF squadrons, including 120 Squadron, an RAAF unit recruited from Dutch pilots, flew the P-40. RAAF Kittyhawks were employed right to the last day of the war, in the Borneo campaign.

Nat Gould

Naval Officers Club member Nat Gould flew both RAF Hurricanes in Russia and RAAF Kittyhawks in Milne Bay. After his first Kittyhawk flight, he wrote, “Don’t like them: too heavy, no climb, no manoeuvrability.” He changed his mind after Milne Bay when he found this “bulldozer with wings” took and delivered more punishment than even his rugged Hurricane. “One Kittyhawk returned to Milne Bay with a hole just forward of the tail big enough to put your head through. That would have destroyed a Hurricane,” Nat said.

RAAF Kittyhawks at Milne Bay (William Dargie painting, 1969).

His log book records Milne Bay sorties ranging from 2¼ hours to 10 minutes. He might fly standing CAP patrols up to 28,000 feet, Anti-shipping Strikes or Army Close Support. Typically, his Kittyhawk carried two 500 lb bombs on Anti-shipping and some Army Support sorties.

The Coastwatchers were the “radar” for 75 and 76 Squadrons. Alerted early enough, the Kittyhawks clawed for a height advantage over the Zeros, Val (Aichi D3A) dive bombers and twin-engined Bettys (Mitsubishi GM4) that routinely raided Milne Bay.

Learning from the failure of the Spitfires over Darwin, they typically avoided dogfighting with Zeros, but on 22 August there was “a dogfight between 22 Kittyhawks and seven Zeros all over the bloody place above the airfield,” Nat recalls. RAAF Log p. 29 says two Zeros were destroyed and three others probably destroyed in this action, with two each Kittyhawks lost from both 75 and 76 Squadrons.

On 25 August, the day before the Japanese landed at Milne Bay, Nat’s 75 Squadron attacked a convoy of two transports escorted by two cruisers and other warships. The cruisers made life hard by firing salvoes deliberately short. Attacking aircraft not only had to contend with torrential rain and low cloud but also the geysers thrown up by the shells. They failed to stop the transports, but Nat and another pilot sank one of the escorting flak ships.

Japanese Type 95 Ha-Go light tank.

Two Japanese Type 95 Ha-Go light tanks landed in support of the 2000 Japanese Marines who invaded Milne Bay. RAAF Kittyhawks isolated another 300+ marines by destroying their barges on Goodenough Island.

Nat agrees that it was essential to learn the “downhill” evasion tactic when sparring with Zeros. He eventually learned an interesting modification, to put the Kittyhawk into a screaming dive and take his hands and feet off the controls. “The aircraft would roll one way and yaw the other, making it a very difficult target.”

Electrics and the Tropics

As may be expected, the mainly electrical-driven ancillary equipment did not take lightly to the humid tropical climate. “It was a great aircraft but one problem was that all the ancillaries, like aileron trim, were electric and in the wet tropics this all-electric machine could produce surprises,” Nat recalled. “Bluey Truscott’s guns fired once when he turned on his nav lights.”

After the dirt, filth, mud, malaria and dysentery of Milne Bay, it is perhaps little wonder that Nat opted to finish the war with the RN, and then join the RAN.

The P-40Q model Kittyhawk had a bigger engine, a four-bladed propeller and a tear-drop canopy. It was never put into production.

The P-40 was a unique aircraft. It could never match the F6F Hellcat, Spitfire, Me 109 or Zero, especially above 15,000 feet as a fighter, but it was rugged, honest and it performed brilliantly as a fighter-bomber. It operated, sometimes with difficulty, in temperate climes, the tropics, the jungle, the desert and in Arctic conditions. Given an altitude advantage, it could take on any contemporary bomber or fighter. Like all aircraft, it had its idiosyncrasies, but these were mastered and readily forgiven by most of the pilots who flew it in war.

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