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Curtiss 81 / 87 / P-40 Warhawk / Kittyhawk / Tomahawk

 

curtissp-40

 

In July 1937 Curtiss installed an 1160-hp supercharged Allison V-1710-19 V-type engine in the 10th production P-36A, designated XP-40 (Model 75P).


The XP-40, flown for the first time on October 14, 1938, and evaluated by the USAAC in the spring of 1939, brought Curtiss a $13 million contract for 524 production aircraft, fitted with 1040-hp Allison V-1710-33 engines, in April of that year. The first three of these were used as prototypes, the first flight by a production P-40 (Curtiss Model 81-A) being made on April 4, 1940.
In April 1939 the US Army Air Corps awarded what was at that time the service’s largest ever fighter contract, covering 524 examples of the P-40. Deliveries of the P-40 order, which had meanwhile been reduced to 200, began in May 1940. Two 0.30-in (7.62-mm) guns were installed above the nose, in the upper engine cowling. The USAAC (or USAAF, as it became in June 1941) gave the name Warhawk to all variants of the P-40.


France, already a major customer for the radial-engined Hawk 75A, ordered 140 Model 81-Als (similar to the P-40), but France had fallen before these could be delivered. They went instead to the RAF, operational with No 2 Squadron in August 1941. These aircraft were given the RAF name of Tomahawk I/IA/IB, equipped with four 0.303-in (7.7-mm) Browning machine-guns (two in the cowling, one in each wing), and used for low-level tactical reconnaissance. The next US production version was the P-40B, of which 131 were built for the USAAF, having the same powerplant as the P-40 but with an additional 0.30-in (7.62-mm) gun in each wing, the calibre of the two nose guns increased to 0.3-in (12.7-mm), and armour protection for the pilot. The RAF received the 110 similar Model 81-A2s of this type intended for France, naming them Tomahawk IIAs. Variant P-40C followed, being similar to the P-40B but with a further 0.30-in (7.62-mm) gun in each wing and improved self-sealing fuel tanks. The first flight took place on April 10, 1941, and 193 were built for the USAAF. Again an order intended for France, for 635 similar Model 81-A3s, went instead to the RAF, these becoming the Tomahawk IIB. A further 295 of this version, supplied to the RAF, were passed on to China (100) and the USSR (195) under the Lend-Lease programme.

In 1941 Curtiss introduced major design changes which earned the Warhawk the new Curtiss Model number 87. The new model was powered by an 1150-hp Allison V-1710-39 engine, equipped with a modified propeller reduction gear which permitted the fuselage, to be shortened by 152 mm (6 in). The undercarriage main-wheel legs were also shortened; the rear fuselage was redesigned, and a deeper nose radiator was fitted. Provi-sion was made for carrying one 227-kg (500 lb) bomb or a 197-litre (43 Imp gal) drop-tank under the fuselage, and smaller bombs could be carried under the wings. Armament was reduced to two 0.5-in (12.7-mm) machine-guns in each wing, the over-nose guns being removed. Most examples of this new fighter-bomber version went to the RAF, which received 560 Model 87-Als as the Kittyhawk 1. Twenty-three similar Model 87-A2s were built for the USAAF as the P-40D, and two were retained by Curtiss for further develop-ment. An increase in armament to six 0.5in (12.7-mm) wing guns led to the Model 87-A3, of which the RAF allocation was 1500 as Kittyhawk 1As, under Lend-Lease, while 820 were delivered to the USAAF as the P-40E.


Meanwhile, one of the two P-40Ds retained by Curtiss became the XP-40F (or Model 87-D) with the installation of a Rolls-Royce Merlin 28 V-type engine; this made its first flight on.June 30, 1941. The Rolls engine offered a far better performance at altitude than the Allison, as a result of which a total of 1311 Merlin-engined P-40Fs were built for the USAAF. Approximately the first 260 of these had the old-style P-40 fuselage, but later models had a 53-cm (20-in) longer, redesigned rear fuselage, which improved low-speed stability. They had the American (Packard)-built version of the Merlin engine, designated V-1650-1 and developing 1300 hp; the air intakes were removed from the top of the engine cowling. These Warhawks were able to carry a 644-litre (142 Imp gal) drop-tank under the fuselage. A consignment of 250 aircraft for the RAF, to have been called Kittyhawk II, were not delivered.


US designations continued with the P40G, allocated to 60 of the original P-40s brought up to six-wing-gun standard in late 1940. The P-40H and J were experimental projects, which never left the drawing-board-the lat-ter was to have utilized a turbocharged Alli-son powerplant, but was deemed unneces-sary after the Merlin-engined version appeared.
The next Warhawk to go into production, and the heaviest, was the P-40K. Built in parallel with the P-40F, it had a 1325-hp Allison V-1710-73 engine, the longer fuse-lage of the later F models, and a small dorsal fin. With an all-up weight of 4540 kg (10000 lb), it was nevertheless capable of 579 km/h (360 mph). Twenty-one were delivered to the RAF as Kittyhawk IIIs, and the USAAF received a total of 1279. The K-series P-40s were produced by the Curtiss plant at Buffalo to a total of 1300 units during the latter part of 1942.

curtissp-40k
P-40K


The first sub type, the K-1, appeared in August 1942 and replaced the "E" model on the production line. However the Merlin-engined "F" series was also in full production by this time so the "F" and "K" continued until they were supplanted by the "L" and 'V' models respectively in late 1942. Early "F" and "K" examples had the original "short" fuselage of all previous P-40 models but, from the P-40F-5 onwards and the K-10 onwards a new one foot eight inch section was introduced aft of the existing fuselage. This additional section supported the fin and rudder but the tailplane and tailwheel were left in their original positions.
The "K's" were very similar to the preceeding "E's" (and succeeding M's" for that matter) with the primary difference being the engine; the V-1710-73 (or V-1710 F4R to use the GM-Allison desig-nation) of preceeding P-40E.


The main external differences from the P-40E were the addition to the P-40K-1 and K-5s of a curved dorsal fin (some late "E's" had this) and the introduction of flared or "fishtail" exhaust ports (round on E,F and L). On the P-40K-10 and K-15s the differences were the lengthened rear fuselage with fin and rudder moved aft of tail plane, a strenthened windscreen assembly with extra bracing strut incorporated in port side only of curved side panel, and a radio mast introduced aft of the cockpit.
This version was followed by the P-40L, a lighter-weight, 'stripped' development of the P-40F, often known for that reason as the 'Gipsy Rose Lee'. It had two fewer wing guns, a lower fuel capacity, and no armour protection, but this resulted in only about 113 kg (250 lb) of weight being saved, and production was therefore limited to the 700 delivered to the USAAF. These were a mixture of long- and short-fuselage models, all powered by V-1650-1 Packard-Merlins. Similar to the K, but with the 1200-hp Allison V-1710-81 engine, the P-40M went in the main to the RAF (595 aircraft, also known as Kittyhawk IIIs), only five being delivered to the USAAF.


Other major external changes which followed were the revised cockpit canopy on P-40N-5 and subsequent models and the fitting of smaller diameter mainwheels (from 30 inch down to 27 inch) except on the P-40N-40-CU. On the "N" model also, the old "ring and bead" type gunsight atop the fuselage nose gave way to a single "bead" just aft of the engine; undercarriage position pins (introduced on the P-40M) protruded above the wing just aft of the undercarriage housing billets when the undercarriage was down; and the large external rear view mirror fitted to most P-40E, F, K, L and M on the support port edge of the windscreen rim was replaced by a smaller interior mirror centrally placed.

Numerically, the major production version in the Warhawk series, and the last, was the P-40N of 1943 after an extensive programme of structural weight saving to provide a higher performance. The USAAF received 4634 of this variant, and the RAF 586 as the Kittyhawk IV. They were powered mainly by the 1200-hp Allison V-1710-81 or -99 engine, but the final 220 of the batch had a 1360-hp V-1710-115 powerplant. Armament comprised four 0.5-in (12.7-mm) wing guns on early models, and six of the same calibre on the later ones, which were also equipped to carry a 680-kg (1500-lb) bombload. The aircraft also featured a lengthened fuselage and redesigned canopy. Thirty P-40Ns were converted to two-seat advanced trainers; two Ks and one N were converted (two of them with 'bubble' canopies) to XP-40Q to test engine cooling equipment, wing radiators and a four-blade propeller. Three hundred P-40Fs and Ls were redesignated P-40R1 and R2 respectively when they were refitted with V-1710-81 engines. 


Prior to the final termination of P-40 development, some effort was expended in combining aerodynamic refinement with increased power to produce a higher-performance model. A P-40K airframe was fitted with an Allison V-1710-121 engine rated at 1,425hp for take-off and 1,100hp at 7620m. Semi-flush low-drag radiators were incorporated in the wing centre section and a four-bladed propeller was fitted, the designation XP-40Q being assigned. A second, similarly re-engined P-40K for the P-40Q programme reintroduced the nose radiator scoop, but featured an all-round vision bubble-type canopy (previously tested on a P-40N). The definitive XP-40Q (converted from a P-40N-25 airframe) had clipped wing tips, the cut-down aft fuselage with bubble canopy and coolant radiators faired into the wing leading edges. Four 12.7mm guns were carried but proposed production models were to have carried, either six 12.7mm or four 20mm weapons. No production was undertaken.

curtissp-40q
P-40Q


When Warhawk production ended in November 1944, Curtiss had built, in addition to the XP-40, a total of 1704 Model 81s and 12 034 Model 87s; annual output being at its highest in 1942 (4453 built) and 1943 (4258), with the greatest number in any one month occurring in August 1943, when 463 were delivered. In addition to widespread use by the USAAF in Europe, North Africa and the Pacific theatres of war, aircraft from the Lend-Lease and ex-French allocations to the RAF (1180 Tomahawks and 3262 Kitty-hawks) were also employed by the Royal Canadian, South African, Australian and New Zealand Air Forces; these too served in the Far East, the Western Desert and Italy as well as in the European theatre. China and the USSR also received P-40s under Lend-Lease, the USSR receiving a total of 2097 aircraft. Their chief role was as close-support low-level attack aircraft.

 

A total of 301 P-40 were allocated to the RNZAF.


The principal versions were P-40 and, in British service, Tomahawk Mk 1(339 aircraft with the 1,160-hp/865-kW V-1710-19 engine), P-40B and Tomahawk Mk IIA (241 aircraft with heavier armament), P-40C and Tomahawk Mk IIB (1,123 aircraft with a revised fuel system), P-40D and Kittyhawk Mk 1(582 aircraft of a P-40C version with 1,150-hp/857-kW V-1710-39, shorter fuselage and shorter landing gear legs), and P-40E and Kittyhawk Mk IA (3,820 aircraft with two additional wing guns).
A total of 13,783 were built, making it the third most numerous American fighter of the war.

 

Gallery

 

 
 
 
Replicas:
Loehle P-40
Jurca MJ-12 P-40
Rowley P-40
Grady Curtiss P-40

 

XP-40 / Model 75P
Engine: 1160-hp supercharged Allison V-1710-19

P-40 Warhawk / Model 81-A
Engine: 1040-hp Allison V-1710-33
Armament: Two 0.30-in (7.62-mm) guns

Model 81-Al / Tomahawk I/IA/IB
Engine: 1,160-hp/865-kW V-1710-19
Armament: four 0.303-in (7.7-mm) Browning machine-guns

P-40B / Model 81-A2 / Tomahawk IIA

Engine: 1040-hp Allison V-1710-33
Armament: 4 x 0.30-in (7.62-mm) guns

P40C / Model 81-A3 / Tomahawk IIB

Span: 11.38 m (37 ft 4 in)
Length:9.68 m (31 ft 9 in)
Gross weight: 3655 kg (8058 1b)
Maximum speed: 547 km/h (340 mph)
Armament: 6 x 0.30-in (7.62-mm) guns

Model 87 / P-40D
Engine: 1150-hp/857-kW Allison V-1710--39
External load: one 227-kg (500 lb) bomb or 197-litre (43 Imp gal) drop-tank + small bombs
Hardpoints: 3
Armament: 4 x 0.5-in (12.7-mm) machine-guns

Model 87-Al / Kittyhawk 1

Engine: 1150-hp/857-kW Allison V-1710--39
External load: one 227-kg (500 lb) bomb or 197-litre (43 Imp gal) drop-tank + small bombs
Hardpoints: 3
Armament: 4 x 0.5-in (12.7-mm) machine-guns

Model 87-A2 / P-40D
Engine: 1150-hp Allison V-1710-39
External load: one 227-kg (500 lb) bomb or 197-litre (43 Imp gal) drop-tank + small bombs
Hardpoints: 3
Armament: 4 x 0.5-in (12.7-mm) machine-guns

Model 87-A3 / Kittyhawk 1A / P-40E Warhawk
Engine: one Allison V-1710-39, 1,150-hp (857-kW).
Maximum speed 335 mph (539 kp h) at 5,000 ft (1,525 m)
Climb to 10,000 ft (3,050 m) in 4 minutes 48 seconds
Service ceiling 29,000 ft (8,840 m)
Range 850 miles (1,368 km).
Empty weight: 6,350 lb (2,880 kg)
Maximum take-off weight: 9,200 lb (4,173 kg).
Wing span 37 ft 4 in (11.38 m)
Length 31 ft 2 in (9.50 m)
Height 10 ft 7 in (3.22 m)
Wing area: 236.0 sq ft (21.92 sq.m).
Armament: six 0.5-in (12.7-mm) machine guns, up to 700 lb (318 kg) of bombs.

Model 87-D / XP-40F
Engine: Rolls-Royce Merlin 28 V-type

P-40F Warhawk / Kittyhawk II

Engine: Packard-Merlin V-1650-1, 1300 hp
Span: 11.38 m (37 ft 4 in)
Length: 10. 16 m (33 ft 4 in)
Gross weight: 4477 kg (9870 1b)
Drop--tank capacity: 644-litre (142 Imp gal)
Maximum speed: 587 km/h (365 mph)

P40G Warhawk
Armament: six-wing-gun

P-40K / Kittyhawk III

Engine: 1325-hp Allison V-1710-73 / V-1710 F4R
All-up weight: 4540 kg (10000 lb)
Max speed: 579 km/h (360 mph)
Vne: 478 mph (415 kt)

P-40K-1

Engine: 1325-hp Allison V-1710-73 / V-1710 F4R

P-40K-10
Engine: 1325-hp Allison V-1710-73 / V-1710 F4R

P-40L
Engine: V-1650-1 Packard-Merlins

P-40M / Kittyhawk III

Engine: 1200-hp Allison V-1710-81

Curtiss P-40N / Kittyhawk IV

Engine: 1 x Allison V-1710-81 or –99, 1,360hp / or 1360-hp V-1710-115
Length: 33 ft 4 in (10.2m)
Wingspan: 37 ft 4 i n (11.42m)
Wing area: 235.947 sq.ft / 21.92 sq.m
Height: 12.37ft (3.77m)
Empty Weight: 6,005lbs (2,724kg)
Maximum Take-Off Weight: 8,858lbs (4,018kg)
Wing load: 37.52 lb/sq.ft / 183.0 kg/sq.m
Maximum Speed: 378mph (609kmh; 329kts) at 3210m
Range: 240miles (386km)
Maximum range: 938 nm / 1738 km
Rate-of-Climb: 2,143ft/min (653m/min)
Service Ceiling: 38,156ft (11,630m)
Armament:
6 x 12.7mm M2 Browning air-cooled machine guns
2,000lbs of external ordnance
Accommodation: 1
Hardpoints: 3 (centre fuselage and two underwing)

P-40N-1
Engine: 1200 hp Allison V1710-81.
Span: 37 ft 4in (11.42m).
Length: 33 ft 4in (10.2m).
Max wt: 8850 lbs (4018 kg).
Max speed: 378mph (609 kph).

XP-40Q
Engine: Allison V-1710-121, 1,425hp take-off /1,100hp at 7620m
Propeller: four-bladed
Armament: Four 12.7mm guns

P-40Q
Wingspan: 10.75 m / 35 ft 3 in
Length: 10.16 m / 33 ft 4 in
Max. speed: 679 km/h / 422 mph

P-40R1
Engine: V-1710-81

P-40R2
Engine: V-1710-81

 

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Curtiss P-40Q

 


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