At a fairly early stage in the development of the Bell P-39 Airacobra, work had been carried out to enhance the per-formance of this aircraft by the introduction of aerodynamic improvements. A line of investigation resulted in a USAAF contract for two “XP-63” prototypes awarded in June 1941. Three experimental aircraft were built, each utilising the basic fuselage of the P-39D, to which were added a new laminar-flow wing with square wingtips and a revised tail unit. In fact, each of the three XP-39Es, as these aircraft were designated, had a different tail unit. It was planned originally to power the prototypes with the Continental Aviation and Engineering Corporation’s IV-1430 12-cylinder inverted-vee piston-engine, which had demonstrated a power output in excess of 1491 kW (2,000 hp). However, Allison V-1710 engines of little more than half of that power output were installed.

As it emerged, the P-63 was similar enough to the P-39Q to be mistaken for it, the P-63A being a low-wing aircraft with tricycle landing gear, mid-mounted Allison engine, car doors on each side of the cockpit, and armament consisting of a 37 millimeter cannon firing through the prop hub, two 12.7 millimeter Brownings on top of the nose, and a single 12.7 millimeter Browning in a fairing under each wing, for a total of five guns.

The P-63 was a generally new design, featuring little parts commonality with the P-39. The P-63 was slightly longer than the P-39, with the most distinctive recognition feature being that the trailing edge of the rudder on the P-63 was straight, while it was rounded on the P-39; the P-63’s tailfin was also taller. Another distinctive recognition feature was a four-bladed prop.

Other changes were subtler. The wingspan and wing area were increased, and the wing featured the new “laminar” airfoil configuration established by NACA. More importantly, the P-63 was powered by an Allison V-1710-93 engine with a second supercharger stage — not a turbocharger, giving it good high altitude performance.

Bell was distracted by producing the P-39 in volume, and the initial XP-63 design turned out to be badly overweight, demanding a redesign. The same basic fuselage design and engine (with two superchargers) was fitted into an enlarged airframe – essentially based on the XP-39E with a laminar flow wing, improved supercharger and new Continental I-1430 engine. Three prototypes were ordered, two with Allison V-1710-47 engines and one with a Packard V-1650 Merlin. The Packard-engined XP-63 was never built. The prototype was powered by an Allison V-1710-93 engine and a four-bladed propeller. Armament remained as the P-39Q model design with a 37mm nose cannons, 12.7mm heavy machine guns in the engine cowl and an additional 2 x 12.7mm heavy machine guns under the wings in pods. The designation was set as Bell Model 33, or P-63 Kingcobra. The first XP-63 (serial number 41-19511) flew on 7 December 1942, though the aircraft was lost in a crash a few weeks later.

The second prototype (serial number 41-19512) took to the air on 5 February 1943, but was lost in a crash in May. Both powered by the 988-kW (1,325-hp) Allison V-1710-47 engine. Fortunately for the program, a third prototype had been ordered in mid-1942. The third prototype, the XP-63A, first flown on 26 April 1943 and powered by a V-1710-93 engine with a war emergency rating of 1119kW (1,500 hp). It was planned subsequently to flight-test this prototype with a Packard-Merlin V-1650-5 engine installed, under the designation XP-63B, but this did not happen.

The type was ordered into production, with the first “P-63A Kingcobra” machines rolled out in October. Some 4,000 aircraft were to be built at Bell’s Marietta, Ohio, facility but were cancelled only three months later.

A total of 50 initial production P-63A-1 machines was built. They were followed by improved subvariants:
The “P-63A-5” was much the same as the P-63A-1 but featured some minor detail changes and new radios. 20 were built.
The “P-63A-6” added a stores attachment under each wing for an external tank or bomb. 130 were built.
The “P-63A-7” was a minor change on the P-63A-6, featuring a modified tailplane with wider span, revised mountings for the nose machine guns, and other fixes. 150 were built.
The “P-63A-8” featured an Allison engine with water-methanol injection, which permitted several minutes of combat power under redline operation, further improving the P-63’s performance. Ammunition supply for the wing guns was cut from 250 to 200 rounds per gun. 200 were built.
The “P-63A-9” was similar to the P-63A-8, but featured more cockpit armour. 445 were built.
The “P-63A-10” replaced the old M4 37 millimeter cannon with the improved M10 model, and also raised the cannon’s ammunition supply from 30 rounds to 58 rounds; the small ammunition supply for the cannon had been a persistent pilot complaint. In addition, the P-63A-10 featured an N-9 lead-computing gunsight. 730 were built.

The first five of these target aircraft were designated RP-63A-11. Five P-63A-9s were initially built as “RP-63A-11” targets, with armor but no armament. They featured the rear cockpit glazing faired over, a modified carburetor scoop, and were fitted with a light on the prop spinner and on each side coupled to an array of sensors that would cause the lights to flash when the aircraft was hit by special “frangible” ammunition broke up on impact. The primary rationale was to train gunners on bombers to counter fighter attacks.

The 95 RP-63A-12s based on the P-63-10 which followed had increased fuel tankage; the next produc¬tion version, with the V-1710-117 engine, became designated RP-63C (200 built) and the final version was the RP-63G (32 built), this having the V-1710-135 engine. RP-63A/C’s were based on five P-63A completed production models modified for the role while at least 95 other A-models were modified as such while still on the production lines. Although never flown as pilotless drone aircraft, the designations of these three versions were changed subsequently to QF-63A, QF-63C and QF-63G respectively.

The Soviet Union operated the P-39 and, with input from Soviet test pilot Andrey G. Kochetkov, the P-63 Kingcobra was modified for the better and ultimately shipped to the Soviet Union from Nome, Alaska, to be used solely against Japanese forces in the East. Despite this “agreement” on the part of the Soviets, P-63 air groups were set up in the West to battle the Germans. The P-63 excelled in the ground attack role, and as tank busters. Soviet use of the P-63 amounted to over 72% of all Kingcobras produced, making them the primary operator of the aircraft.

Equipment of production batches varied considerably, resulting in many sub-types. The first production P-63A-ls had V-1710-93 engines, a nose-mounted 37-mm M4 cannon and two 12.7-mm (0.5-in) machine-guns in underwing fairings; other sub-types had two additional 12.7-mm (0.5-in) guns mounted in the fuselage nose. P-63A-ls and P63A-5s could accommodate a 284-litre (75-US gal) or 662-litre (175-US gal) drop tank, or a 237-kg (522-lb) bomb beneath the wing centre-section; P-63A-6s had underwing racks for two similar bombs or additional fuel; and P-63A-10s could mount three air-to-surface rockets beneath each wing. The weight of defensive armour, intended primarily to give protection from ground weapons, increased progressively from 39.8 kg (87.7 lb) on the P-63A-1 to 107.2 kg (236.3 lb) on the P-63A-10.

A “P-63B” variant with a Rolls-Royce Merlin engine was considered but never built, and so the next Kingcobra variant was the “P-63C”. The P-63A was succeeded on the production line by the P-63C with the improved V-1710-117 engine, this offering with water injection an emergency war rating of 1342 kW (1,800 hp), wingspan clipped by 25 centimeters (10 inches) and, after early production at least, a prominent ventral fin to improve yaw stability; it is unclear if the fin helped reduce the aircraft’s propensity to spin.

The “P-63C-1” was the initial production subvariant, with 215 built; they were followed by 1,012 “P-63C-5” machines with minor improvements. 200 more P-63C-1 machines were manufactured as “RP-63C-2” Pinball targets, for a total of 215 + 1,012 + 200 = 1,427 P-63C machines built.

Only one “P-63D” – technically a “P-63D-1” – was built. It was similar to the P-63A-10, with no ventral fin, but featured a bubble canopy and the carburetor intake moved back, presumably to allow the canopy to be slid back to open. The wingspan was increased over that of the P-63A, to 11.94 meters (39 feet 2 inches); the P-63D was powered by an Allison V-1710-109. The aircraft was lost in a crash due to an engine fire that claimed the life of pilot Bob Borchardt.

The P-63D was followed by the “P-63E”, which was along the lines of the P-63C-10, with the ventral fin and the M10 cannon, but with the wider wingspan, stepped-back carburetor intake, and V-1710-109 engine of the P-63D. It retained the old car-door cockpit scheme; it featured more fuel capacity and a new Aeroproducts propeller.

Thirteen of the P-63E (or Bell Model 41), all that had been produced of 2,930 on order when contracts were cancelled at the war’s end, and which were generally similar to the P-63D except for a reversion to the standard cockpit canopy. The P-63E was similar to the D-model but sported the original automotive-style doors of the P-39 Airacobra and P-63A and P-63C Kingcobras. The underside fin was extended some and a new propeller were fitted though only 13 examples of this Kingcobra made it out the door. The E-model exhibited a top speed of 408 miles per hour, a cruising speed of 280 miles per hour, a range of 450 miles and a service ceiling of 43,000 feet.

There were two P-63F-1 built on an experimental basis. A version of the P-63E with a V-1710-135 engine and modified tail surfaces and substantially taller tailfin.

The XP-63H was a single conversion attempt based on a modified P-63E and featuring a new engine.

One other unusual version of the King-cobra was built extensively (in excess of 300) for use by the USAAF in a training programme involving the use of live ammunition. Developed from the P-63A, all armour and armament was removed, and the external surface of the wings, fuselage and tail unit were protected externally by the addition of a duralumin alloy skin weighing some 680kg (1,500 lb). Other protection included the installation of bulletproof glass in windscreen and cockpit side and upper windows, the provision of a steel grille over the engine air intake and steel guards for the exhaust stacks, and the use of a propeller with thick-walled hollow blades All of these precautions were to make possible for the aircraft to be flown as a target that could withstand, without significant damage, the impact of frangible bullets. When a hit was made by an attacking aircraft a red light blinked to confirm the accuracy of the weapon being fired against it.

The first five of these target aircraft were designated RP-63A-11; the 95 RP-63A-12s which followed had in-creased fuel tankage; the next production version, with the V-1710-117 engine, became designated RP-63C (200 built). The final production version of the Kingcobra was the “RP-63G” Pinball target, with 32 built, for a total of 100 + 200 + 32 = 332 Pinballs. The RP-63G had the V-1710-135 engine. RP-63A/C’s were based on five P-63A completed production models modified for the role while at least 95 other A-models were modified as such while still on the production lines. Although never flown as pilotless drone aircraft, the designations of these three versions were changed subsequently to QF-63A, QF-63C and QF-63G respectively. The Pinballs remained in service after the war, but were generally retired in 1947.

Two P-63C production models were converted into L-39 test aircraft for swept wing and wind tunnel evaluation.

Bell considered but never built a trainer version, though the company did add a secondary cockpit on the rear fuselage to one P-63A and two P-63Es, the rear cockpit being used to seat an observer to keep an eye on trials aircraft. The Soviets did perform at least three conversions of P-63As to “TP-63A” trainer configuration, with a configuration along the lines of that of the TP-39 trainers.

At the time of their production, a single P-63 cost American tax payers $48,000 to produce. A total of 3,303 were built.

A P-63A was converted in 1945 as a test-bed for a V-tail.

The XP-63N was a 1948 RP-63G conversion for V-tail testing.

The Soviets were the primary users of the P-63, obtaining about 2,400, air ferried by the Siberia route. P-63s shipped to the USSR never saw combat against the Nazi Reich; the Soviets had plenty of fighter aircraft at the time, and being intent on performing a thorough evaluation of the Kingcobra before putting it into service, it was not available to frontline units before the Nazi surrender in May 1945. Some Red Air Force pilots recollected seeing P-63s in service against the Germans, but no records confirm this.

The P-63 did see action in the brief Soviet campaign against the Japanese before Japan’s surrender in August 1945, primarily being used for escort and ground attack.

After the war, the P-63 remained in first-line Red Air Force service. It was seen as very useful in helping pilots convert to new jet fighters as they came into service, since the jets generally had tricycle landing gear. The Kingcobra lingered on the flightlines into the early 1950s. There are tales that US pilots encountered them during the war in Korea, but no documentation confirms that notion.

The only other serious export user of the Kingcobra was the French Armee de l’Aire, which received 114 P-63Cs at the end of World War II. They served in combat as ground-attack aircraft in the French war in Indochina, being finally retired in 1951 in favour of US-supplied Grumman F8F Bearcat piston fighters. Some P-63s lingered in liaison and other secondary roles for a few years after that.

The Kingcobra was out of military service by the mid-1950s, but a few surplus P-63s did have a new career as air racers in the postwar period. A number of Kingcobras survive as museum displays, while a few remain flying as airshow “warbirds”.

Including the Pinballs, a total of 50 + 20 + 130 + 150 + 200 + 445 + 730 + 5 + 95 = 1,825 P-63A machines was built.

Gallery

XP-39E
Engine: Allison V-1710

XP-63
Initial prototypes
Engine: 988-kW (1,325-hp) Allison V-1710-47
3 built

XP-63A
Engine: Rolls-Royce Merlin V-1710- 93 1119kW (1,500 hp)

P-63A Kingcobra
Initial production machines
Engine: one 988-kW (1,325-hp) Allison V-1710-93 inline piston
Maximum speed 660 km/h (410 mph) at 7620m (25,000ft)
Cruising speed 608 km/h (378 mph)
Service ceiling 13110m (43,000 ft)
Range maximum weapon load and internal fuel 724 km (450 miles)
Ferry range maximum internal and external fuel 3541 km (2,200 miles)
Empty weight: 2892 kg (6,375 lb)
Maximum take-off 4763 kg (10,500 lb)
Wing span 11.68m (38ft 4in)
Length 9.96m (32ft 8in)
Height 3.84m (l2ft 7in)
Wing area 23.04sq.m (248 sq ft)
Armament: one 37-mm M4 cannon, two wing-mounted and two nose¬mounted 12.7-mm (0.5-in) mg, plus up to three 237-kg (522-lb) bombs.

P-63A Kingcobra
Wingspan: 11.68 m / 38 ft 4 in
Wing area: 23.04 sqm / 248 sq. ft
Length: 9.96 m / 32 ft 8 in
Height: 3.84 m / 12 feet 7 in
Empty weight: 2,892 kg / 6,375 lb
MTO weight: 4,763 kg / 10,000 lb
Max speed at altitude: 660 KPH / 410 MPH / 355 KT
Service ceiling: 13,100 m / 43,000 ft
Range: 725 km / 450 MI / 390 NMI

P-63A-l
Engine: Allison V-1710-93
Armament: nose-mounted 37-mm M4 cannon and two 12.7-mm (0.5-in) machine-guns in underwing fairings; other sub-types had two additional 12.7-mm (0.5-in) guns mounted in the fuselage nose.

P-63A-1
284-litre (75-US gal) or 662-litre (175-US gal) drop tank, or a 237-kg (522-lb) bomb beneath the wing centre-section

P-63A-5
284-litre (75-US gal) or 662-litre (175-US gal) drop tank, or a 237-kg (522-lb) bomb beneath the wing centre-section

P-63A-6
284-litre (75-US gal) or 662-litre (175-US gal) drop tank, or a 237-kg (522-lb) bomb beneath the wing centre-section, underwing racks for two similar bombs or additional fuel

P-63A-7
Engine: Allison V-1710-93, 1325 hp

P-63A-10
Three air-to-surface rockets beneath each wing.

P-63C
Engine: Allison V-1710-117/E21, 1342 kW (1,800 hp) / 1100 hp @ 25,000 ft.
Length: 32.81ft (10m)
Width: 38.39ft (11.70m)
Height: 12.47ft (3.80m)
Empty Weight: 6,834lbs (3,100kg)
Maximum Take-Off Weight: 8,818lbs (4,000kg)
Maximum Speed: 410mph (660kmh; 356kts)
Maximum Range: 450miles (725km)
Rate-of-Climb: 2,500ft/min (762m/min)
Service Ceiling: 42,979ft (13,100m)
Armament:
1 x 37mm cannon in propeller hub
4 x 12.7mm machine guns (2 x in nose; 2 x in wing assembly).
Accommodation: 1
Hardpoints: 3
Number built: 1227

P-63C-5
Engine: Allison V-1710-117, 1325 hp
Wingspan: 38 ft 4 in
Wing area: 248 sq.ft
Length: 32 ft 8.5 in
Empty weight: 6694 lb
Loaded weight: 10,700 lb
Max speed: 410 mph at 25,000 ft

P-63D
Engine: Allison 109/E22, 1100 hp @ 28,000 ft.
Number built: 1

P-63E / Bell Model 41
Engine: Allison 109/E22, 1100 hp @ 28,000 ft

P-63F
Engine: Allison V-1710-135, 1450 hp / 1081 kW

RP-63A-11 / QF-63A

RP-63A-12 / QF-63C

RP-63C / QF-63G
Engine: Allison V-1710-117

RP-63G
Engine: Allison V-1710-135
32 built

Bell had been working on a single-seat fighter, the “Bell Model 3”, in response to a 1936 US Army Air Corps (USAAC) requirement. As the design emerged, it was a low-wing monoplane with tricycle landing gear, then an unusual feature, with the engine unconventionally mounted in mid-fuselage, turning the propeller through a driveshaft. This arrangement, which had been used in a few earlier experimental aircraft, was seen as enhancing agility by placing the engine at the machine’s center of gravity (CG), as well as permitting installation of heavy armament in the nose. There was some thought of putting the cockpit behind the engine, close to the tail – but that was quickly judged unrealistic, with the cockpit moved forward of the engine, this revision being designated the “Model 4”.

Bell P-39 Airacobra Article

The Bell proposal was submitted to the Air Corps in May 1937, with the USAAC awarding a contract for a single prototype of what had by then become the Bell “Model 12”, more formally “XP-39”, in October of that year.

The 1938 Airacobra was single-seat fighter with a tricycle landing gear, a single Allison V-1710-17 liquid-cooled engine of 1,150 horsepower (860 kW) located behind and below the pilot and driving the propeller by means of an extension shaft, and a cannon firing through the hollow propeller shaft (in addition to fuselage-mounted machine-guns). A turbosupercharger was mounted on the port side of the fuselage. The aircraft featured a scoop on each side of the engine for the turbocharger system.

Though the XP-39 wasn’t armed armament was envisioned as an Oldsmobile M-4 37mm cannon mounted in the upper forward portion of the fuselage nose with the barrel protruding and firing out through the propeller hub, two 12.7mm Browning machine guns in the upper-forward portion of the fuselage and additional 12.7mm (.50 caliber) machine guns were added to either wing – one to a wing.

Initial flight of the XP-39 prototype was on 6 April 1939, with test pilot James Taylor at the controls.

On the basis of satisfactory initial test flights, the Air Corps awarded Bell a contract to produce a dozen “YP-39” evaluation machines – with the order then augmented with a 13th machine that was originally planned as the “XP-39A” – to feature changes recommended in light of studies by the US National Advisory Committee for Aviation (NACA). While work went on to build these machines, the XP-39 was rebuilt to the “XP-39B” configuration, the primary change being that the turbocharger system was deleted, with the Allison engine reverting to its standard single-stage supercharger. The air intake was now moved to the upper portion of the fuselage and another Allison engine was selected for production that would provide better low-level performance. The XP-39 was the only Airacobra to be fitted with a turbocharger system.

It appears that NACA wind tunnel experiments showed the XP-39 turbocharger installation was so aerodynamically cluttered that it did more harm than good. The XP-39B deleted the scoops for the turbocharger, and instead featured a small but distinctive carburetor intake on the spine of the aircraft. The re-born XP-39B performed its initial flight on 25 November 1939.

The first of the batch of YP-39s performed its initial flight on 13 September 1940, with all delivered by the end of the year. They also used a supercharger instead of turbocharger; the later YP-39 machines in the evaluation batch featured armament. Even before the first flight of YP-39, the Air Corps had ordered a batch of production machines, originally designated “P-45” but then designated “P-39C”, their configuration being much like that of the armed YP-39s. The first P-39C flew in January 1941.

The P-39C really wasn’t suitable for combat, lacking armor and self-sealing tanks. 80 had been ordered, but only 20 were built, combat reports from Europe indicating that the P-39C was simply not up to combat duty. The remaining 60 machines in the order were built with armor, self-sealing tanks, and enhanced armament as the “P-39D”. The P-39C ended up being an evaluation type, with the P-39D being the first Airacobra to go into formal service with the Army Air Corps. It would also be the first “Cobra” variant to see action.

The initial production P-39 systems became the P-39C models and were quickly followed by the P-39D series. The aircraft almost took on the designation of P-45 due to the radical list of changes from the original proposal through it was eventually settled that the P-39 designation was sufficient in detailing the significant changes and additions. P-39C models had a pair of 7.62mm (.30 caliber machine guns) mounted in between the existing 12.7mm heavy machine guns. Sixty examples of the ordered P-39C models effectively removed the 12.7mm heavy caliber wing-mounted machine guns and replaced them with 4 x 7.62mm types (two machine guns to a wing with 1,000 rounds each) and became P-39D designations while still retaining their nose-mounted 12.7mm heavy machine guns (300 rounds each). The M4 37mm cannon (30 rounds) was still in place. The P-39C had only 15 rounds of ammunition. The P-39C also had two 7.62 millimeter Brownings on the bottom of the nose, but they were deleted for the P-39D.

The pilot got in and out of the cockpit through a car-style side door, with a door on each side. The doors even had roll-down windshields. They made access to the aircraft easy, though they also made escape a bit tricky in a pinch; and they were rigged so they could discarded to simplify bailing out.

Construction was mostly of aircraft aluminum, with some magnesium parts and fabric-covered flight surfaces. All the landing gear assemblies had single wheels, with the nose wheel castoring and ground steering by differential braking. The nose gear retracted backward and the main gear hinged in the wings to pivot towards the fuselage. The engine was a V-1710-35 Allison, also with 860 kW (1,150 HP) but with technical improvements, driving a three-bladed Curtiss Electric variable-pitch propeller. Self-sealing fuel tanks were fitted in the wings; trim considerations made installing fuel tanks in the fuselage problematic, the engine preventing them from being installed on the CG, and the relatively small size of the wing tanks meant modest range.

There was a centerline stores rack, capable of handling stores of up to 225 kilograms (500 pounds). Although the P-39D was used for trials of various configurations of belly tanks for ferry flights, it is unclear if the P-39D ever carried a belly tank in service.

A total of 429 baseline P-39Ds was built, followed by 336 “P-39D-1” machines, the primary difference being replacement of the M4 37 millimeter nose cannon with a 20 millimeter Hispano Mk.404 cannon with 60 rounds of ammunition. It appears the substitution was due to production difficulties with the 37 millimeter cannon. The P-39D-1 also featured a small fillet on the front of the tailfin where it merged with the top of the fuselage; sources are a bit unclear as to whether the fillet was actually fitted to the baseline P-39D, but it certainly didn’t appear on the P-39C.

Following the P-39D-1, Bell built 158 “P-39D-2” machines, much the same as the P-39D-1 but with very minor tweaks. In addition, a total of 26 P-39D-series aircraft was converted to a photo-reconnaissance configuration, the “P-39D-3”, by placing two cameras in the aft fuselage and adding a bit of armor. It is unclear if they retained full armament. They were followed by 11 similar “P-39D-4” conversions. Total production of the D-series was 429 + 336 + 158 = 923 aircraft.

Roughly in parallel with P-39D production, Bell manufactured a total of 675 “P-400” Airacobras for export. The French had bought a batch of P-400s in April 1940; the order was taken over by the British after the fall of France a few months later, with the British then substantially increasing the buy. The P-400 was very similar to the P-39D-1, with the 20 millimeter Hispano cannon, but instead of 7.62 millimeter Brownings in the wings it featured 7.7 millimeter (0.303 caliber) Brownings for compatibility with British ammunition.

While the P-39 Airacobra had established a record as a competent if unspectacular low-altitude fighter, the same could be said of most Russia-produced fighters. The P-39 was a welcome reinforcement but it brought nothing new to the table. What the Russians really needed was a fighter capable of higher-altitude operations. This would allow them to take the battle to the Luftwaffe whose fighter had a major performance edge above the 12,000 to 16,000 foot band where existing Russian aircraft peaked out. Addressing this requirement led to the development of the P-45 Kobrushka. Although the P-45 was essentially a development of the original P-39 prototype with its turbocharged engine, its development was the outcome of tactical considerations and early war experience. The usual statement that the P-45 Kobrushka formed an intermediate stage between the P-39 and the much more formidable P-63 Kingcobra is also only partly true and the two should be regarded as parallel developments.

Experience from the Russian front showed that the limited operational ceiling of the P-39 was a serious problem and that, when flying at its upper altitude limits, the Airacobra was extremely vulnerable to any enemy fighter with decent high altitude performance. In April, 1943, three P-39Ds were ordered modified with a 1,325 hp Allison V-1710-47 engine equipped with a turbocharger and driving an Aeroproducts propeller. This aircraft was designated the XP-39E and carried the same armament as the P-39D but featured a new wing with square-cut tips. This wing was redesigned internally to provide for the carriage of a .50 caliber machine gun within the wing rather than under it as with the P-39. Wing span and gross area were increased to 35 feet 10 inches and 236 square feet. The most noticeable feature was the provision of air intakes on the side of the fuselage for the turbocharger. These were designed so they contributed a small amount of thrust to the aircraft’s propulsion. Each of the three examples tested different vertical tail surfaces—the first being conical, the second being cut-off square and rather short, and the third being similar to the second but larger. The carburetor air intake was relocated and the wing-root radiator intakes were enlarged. The fuselage was lengthened by 1.75 feet to accommodate the longer -47 engine. These changes were so extensive that the aircraft was redesignated the P-45. Since it was primarily intended for supply to the Russian Air Force under lend lease, it was officially dubbed the Kobrushka

During tests, a maximum speed of 386 mph at 21,680 feet was attained, which was much better high-altitude performance than other Airacobra variants. An altitude of 20,000 feet could be reached in 6.3 minutes. The P-45 had a much better high-altitude performance than other Airacobra variants and no less than 4000 were ordered by the USAAF, mostly for supply to the Russians.

The P-45A was virtually identical to the XP-45 except that the 37mm cannon was replaced by an M2 20mm cannon with 100 rounds of ammunition. Experiments had shown that the tall, squared off tail fin offered the best characteristics and this was adopted for the production version. The first P-45As entered USAAF service in December 1943 and were enthusiastically received by their pilots who considered the type equal to the Me-109G and FW-190A. This experience led to a decision to issue the P-45A to selected USAAF units.
Large numbers of P-45As were supplied to Russia and equipped the Guard (ie. elite) Fighter Regiments 16 GIAP, 19 GIAP, 21 GIAP, 72 GIAP, 100 GIAP, 213 GIAP (previously 508 IAP) and Fighter Regiments 196 IAP, 255 IAP, 508 IAP (later 213 GIAP). In Russian use, P-45s were often given to pilots who had proved their ability with the P-39. Several Russian Kobrushka aces are known. Lieutenant Colonel of the Guards Alexander I. Pokryshin, a Soviet ace with 59 kills to his credit, scored 48 of these in a P-45. He was awarded the Distinguished Flying Cross by President Roosevelt. There are eight other P-39 and P-45 pilots with at least 20 kills. Among top Airacobra aces were Grigorii A Rechkalov (44 kills) , Nikolai D Gulayev (36 kills), Ivan I Babak, Aleksandr F Klubov, Andrei I Trud, and the brothers Boris B Glinka and Dmitrii B Glinka

The Russian pilots preferred their 20-mm Shvak cannon over the 37mm of other P-39 Airacobra variants because of its greater reliability. In addition, the trajectory of the shells from the 20-mm cannon more closely matched that of the 0.50-inch guns, making for a greater concentration of fire. In the P-39G, the Soviets usually removed the wing guns or had them removed at the factory, preferring a better performance over the enhanced firepower. These considerations lead to the development of the P-45B that was built with a 20mm Shvak cannon replacing the M2 20mm gun. The P-45B retained the two nose-mounted .50 caliber machine guns. Two more .50s were mounted, one in each wing. Originally the P-45B was intended purely for Russian use but American pilots tried the aircraft and approved mightily of the new armament. Accordingly, production was increased and American units started to receive the P-45B. 20mm Shvak cannon were supplied for these aircraft by the Russians, the guns being flown back as cargo for return trips on the Air Bridge. Performance of the P-45B was identical to that of the A model.

The use of the 20mm Shvak cannon eased maintenance of Kobrushkas in Russian units so it was natural to consider a wholly-Russian-armed version of the aircraft. Accordingly, the P-45C was designed, equipped with a single 20-mm B-20 cannon and two or four 12.7mm Berezin UBS machine guns. The B-20 and UBS were virtually the same gun, simply being chambered for different rounds. This eventually led to a rationalization of the armament with the definitive P-45C carrying three 20mm B-20 cannon in the nose. Although all P-45Cs produced were shipped to Russian fighter units, late production P-45Bs in U.S. service had the B-20 gun in place of the heavier ShvaK. Many USAF P-45Bs were re-armed with three B-20 cannon in the nose and two .50 machine guns in the wings.

Produced for both the Russian and American air forces, the P-45D standardized on an armament of three 20mm B-20 guns in the nose. U.S. aircraft carried an additional two M2 or UBS .50 machine guns in the wings. The most obvious visual change was the replacement of the original cockpit with its characteristic side doors by a sliding bubble canopy.”

However, British expectations of the “Airacobra I” – as it was designated in Royal Air Force (RAF) service – had been set by performance figures established by the unarmed and unarmored XP-39 prototype. On evaluation, the P-400 turned out to be about 10% slower than advertised, and of course its high-altitude performance was pathetic. It should be noted, however, that Bell engineers were correct in believing the mid-mounted engine was good for maneuverability, the RAF report concluding that an Airacobra could easily out-turn a Messerchmitt Bf-109.

Only a portion of the P-400 order was delivered to the UK, serving for a short time with RAF Number 601 Squadron, “City Of London”. The RAF performed a single combat mission with the type before withdrawing it from service. The remainder of the batch was shipped to the USSR or was taken in to US Army Air Forces (USAAF) service – the “Air Corps” having been superseded by the “Air Forces” in June 1941. The P-400s saw combat in the South Pacific; it is likely they were fitted with 7.62 millimeter Brownings, though sources are unclear on the matter.

The completed P-39C and D models initially went to war with the 31st Pursuit Group (later becoming “Fighter” Group). As a bombing platform, a single 500lb bomb was mounted to the centerline fuselage

The P-39D left something to be desired in service, suffering from a range of teething problems such as gear that was unreliable or froze up and other deficiencies. Deficiencies were addressed in subsequent variants, initially with a confusing list of P-39 variants built in small or relatively limited numbers:

The “XP-39E”, which was a substantially modified experimental machine, with a 53 centimeter (21.3 inch) fuselage stretch, more fuel capacity, and wider wings plus tailplane. All flight surfaces had squared-off tips, with the tailfin fitted with a prominent leading-edge fillet later in development. It was supposed to have been used to evaluate the Continental V-1430 engine, but non-availability of such meant it was powered by an Allison V-1710-47 engine with a two-stage supercharger instead. Three were built; despite all the changes, its performance was no better than that of the P-39D, and so that line of investigation was abandoned.

The “P-39F” was almost identical to a P-39D with the M4 37 millimeter cannon, but had an Aeroproducts three-bladed prop, since Curtiss was having problems making deliveries. 210 were built, with 27 given minor improvements and redesignated “P-39F-2”.

There was an intent to build a “P-39G” variant, but the aircraft planned for that build ended up getting other designations. There was no “P-39H” nor “P-39I”; the USAAF didn’t like to use the “I” suffix because it was too easy to confuse with a “1” and end up with “P-391”, but what happened to the P-39H designation is unclear. That means the P-39F series was followed in production by the “P-39J”, which was much like the P-39F, but had a slightly improved Allison V-1710-59 engine. 25 P-39Js were built.

The “P-39K” featured the further improved V-1710-63 engine. 210 were built, all under the designation of “P-39K-1”, there apparently not being a P-39K (no block number) subvariant. Six were slightly modified as “P-39K-2” machines, with one P-39K-1 altered as the “P-39K-5” testbed, with a V-1710-85 engine, a wider Aeroproducts prop, and other changes.`

The “P-39L” was much the same as the P-39K, except for fit of a Curtiss Electric propeller with a diameter of 3.15 meters (10 feet 4 inches). 250 were built under the designation of “P-39L-1” – there was no P-39L subvariant – with 11 modified to “P-39L-2” reconnaissance machines.

The “P-39M” was similar to the P-39L, but had a V-1710-67 engine with improved high-altitude performance. 240 were built under the designation of “P-39M-1”, with 8 converted to “P-39M-2” reconnaissance machines. It appears that the P-39M was the first Airacobra to carry a centerline external tank as a normal fit, tank options being either 284 liters (75 US gallons) or 662 liters (150 US gallons).

The baseline P-39N featured a V-1710-85 engine and a 3.18 meter (10 foot 4 inch) Aeroproducts prop; a P-39K was modified as the series prototype. 500 of P-39Ns were built, with all but the first 160 featuring elimination of three internal fuel cells to reduce weight. The P-39N could of course carry an external tank to compensate for the smaller internal fuel load, and service units that wanted the full internal fuel load back could install a field upgrade kit to restore the deleted fuel cells. Several further P-39N subvariants were built:
The “P-39N-1” featured a wider 3.51 meter (11 foot 7 inch) Aeroproducts propeller. 900 P-39N-1s were built.
The “P-39N-2” was a photo-reconnaissance conversion of 128 P-39N-1 machines.
The “P-39N-3” was a photo-reconnaissance conversion of 35 baseline P-39N machines.
The “P-39N-5” was a P-39N-1 with armor plate replacing the cockpit rear armor glass. 695 were built for a total P-39N production of 500 + 900 + 695 = 2,095 aircraft.

More P-39Qs built than the rest of P-39 production put together. Subvariants of the P-39Q included:
The “P-39Q-1” was much like the P-39N, retaining the V-1710-85 engine, but replaced the two 7.62 millimeter machine guns in each wing with an underwing fairing stowing a single 12.7 millimeter machine gun — for total armament of four 12.7 guns plus the 37 millimeter cannon. Pilots had complained the 7.62 millimeter guns were ineffectual, with Soviet pilots calling them “paint scratchers”. 150 P-39Q-1 machines were built.
The “P-39Q-2” was a photo-reconnaissance conversion of 5 P-39Q-1 machines.
The “P-39Q-5” was much the same as the P-39Q-1 but restored the deleted fuel tankage. 950 were built.
The “P-39Q-6” was a photo-reconnaissance conversion of 148 P-39Q-5 machines.
The “P-39Q-10” was similar to the P-39Q-5 except for various minor tweaks, for example improved winterization — presumably at Soviet request, the bulk of P-39Q production going to the USSR. 705 were built.
The “P-39Q-11” was a photo-reconnaissance conversion of 8 P-39Q-10 machines.
The “P-39Q-15” was similar to the P-39Q-10 except for minor tweaks, such as reducing the number of oxygen bottles from 4 to 2. 1,000 were built.
The “P-39Q-20” was in turn similar to the P-39Q-15 but with further minor tweaks. Most were delivered to the USSR, with the wing guns deleted from these machines; the Soviets thought that two 12.7 millimeter guns and the 37 millimeter cannon provided perfectly adequate armament, and wanted the wing guns deleted to save weight. In fact, they had been yanking the wing guns from earlier P-39Q machines after delivery. The wing guns were similarly deleted from later P-39Q subvariants sent to the Soviet Union. 891 P-39Q-20 machines were built.
The “P-39Q-21” was similar to the P-39Q-20, but had a four-bladed Aeroproducts propeller. 109 were built.
The “P-39Q-25” was similar to the P-39Q-21, but had a reinforced rear fuselage and tailplane. 700 were built.
The “P-39Q-30” was similar to the P-39Q-25 but reverted to the three-bladed propeller; it also featured minor tweaks. 400 were built, for total P-39Q production of 150 + 950 + 705 + 1,000 + 891 + 109 + 700 + 400 = 4,905 aircraft.

The Airacobra was successfully operated with radio-control as a remote-controlled target drone. Two P-39Qs were actually obtained by the US Navy for use as radio controlled drones, being initially designated “XTDL-1” and then “XF2L-1K”.

Additional variations also included a dual-seat trainer version. Bell modified a P-39Q-5 to “TP-39Q-5” configuration by removing the armament, adding a forward cockpit with a side-hinged canopy up front for a flight instructor, and adding a ventral strake under the tail and an extended forward tailfin fillet to handle aerodynamic changes. It was rolled out in September 1943.

That experiment proving satisfactory, Bell converted 12 P-39Q-20 machines to a similar “RP-39Q-22” configuration, the “R” indicated “restricted”, as in not suitable for combat. A few were supplied to the USSR; the Red Air Force thought it a good idea, and so developed a few Airacobra trainer conversions of their own, designated “UTI P-39”; they had a different forward canopy arrangement.

The Soviets received 4924 P-39s. The P-39 made many-an ace for the Soviet Air Force where air-to-air battles along the East Front typically unfolded under the optimal 10,000 feet ceiling limit of the Airacobra. Aleksandr Ivanovich Pokryshkin, the third highest scoring Allied ace, earned 60 Luftwaffe victims flying in his P-39. Similarly, Grigori Rechkalov – the second top scoring Soviet ace – earned 44 such victories piloting a P-39. Initial P-39 deliveries to the Soviet Union arrived with the British-selected 20mm Hispano-Suiza nose cannon while later models came with the more potent American-endorsed M4 37mm cannon – the latter adjustment making quite a difference. The United States did not deliver the M80 AP round for these autocannons through Lend-Lease. In their place came 1.2 million rounds of M54 HE rounds, proving useful for air and soft ground targets. As such, the Soviet P-39s were not used in the dedicated “tank-busting” role.

With most Italian fighter production in the hands of the fascist state in northern Italy after the armistice of September 1943, the Allies had to provide the co-belligerent Italians of the south with any modern equipment, including fighters. Several Italian fighter squadrons were tasked with fighter-bomber support of the Yugoslav partisans during 1944, and these units were provided with 149 examples of the P-39 Airacobra. The two variants involved were the P-39N with the V-1710-85 engine and the P-39Q with the mixed machine-gun battery of earlier models replaced by a homogenous battery (two 12.7-mm/0.5-in guns in the nose cowling and single guns in the blister under each wing). Late aircraft also introduced a four-rather than three-blade propeller, and had altered fuel capacity and armour protection: The type was retired only in 1951.

Portugal interned eighteen P-39s that landed on their soil, ultimately applying payment to the United States for these captured systems at the end of the war.

The Royal Australian Air Force received a mix of D- and F-models pending the Japanese invasion of the Australian mainland. These were returned to the United States when the threat officially subsided.

The Free French obtained almost 250 Airacobras from mid-1943 in the Mediterranean theater, but they were phased out in favor of the Republic P-47 by late 1944.

The USAAF 31st Fighter Group was set up and comprised of the 307th, 308th and 309th Fighter Squadrons with P-39s. These arrived in England in July of 1942. Seeing prompt action, and in one fighter sweep, six of the twelve P-39s were lost to enemy action. It was not long after that the USAAF pulled the Airacobra form the theater, replacing the 31st Fighter Group P-39s with Supermarine Spitfires. Still, P-39s saw combat actions in support of the Operation Torch landings over North Africa and then over Italy. These primarily flew under the 10,000-foot ceiling limit, used in the close-support role and escorted by fighters.

One USAAF pilot, Lieutenant Bill Fiedler, became an ace in the Airacobra, while several other USAAF pilots scored kills with it.

The P-39 was set into service in the Panama Canal zone under fear of an attack from either ocean from Japanese or German submarine groups.

After the attack on Pearl Harbor (December 7th, 1941) the P-39 was pushed into the Pacific Theater of War and saw its first recorded combat with the 8th Pursuit Group. Following the initial P-39C and P-39D models were the P-39F and P-39G model series with Aeroproducts propellers.

Japan mounted an invasion across the Aleutian island chain off of Alaska in an effort to setup submarine replenishment points for actions in the Northeast Pacific. P-39s defensed against targets of opportunity including flying boats, shipping vessels, airfields and depots. In all, 20 enemy aircraft were destroyed for the loss of just one P-39.

Some 9,584 P-39s were produced at the cost of $50,666 dollars each. Production ran from 1940 to May of 1944.

Gallery

XP-39
No built: 1
Turbocharged initial prototype.

YP-39
No built: 13
Evaluation machines

XP-39B
No built: 1
Rebuilt initial prototype

P-400
No built: 675
With 20 mm cannon for RAF, most flown by USAAF.

P-39C
No built: 20
Preproduction machines

P-39D
Engine: Allison V-1710-3
Wingspan: 10.36 m / 34 ft
Wing area: 19.79 sq.m / 213 sq.ft
Length: 9.19 m / 30 ft 2 in
Height: 3.61 m / 11 ft 10 in
Empty weight: 2,475 kg / 5,460 lb
MTO weight: 3,720 kg / 8,200 lb
Max speed: 580 KPH / 360 MPH / 315 KT
Service ceiling: 10,000 m 33,000 ft
Range: 960 km / 600 MI / 520 NMI
No built: 923
Initial full production variant

P-39F
Engine: Allison V-1710-35
No built: 229
Like P-39D, but with Aeroproducts prop

P-39J
Engine: Allison V-1710-59
No built: 25

P-39K
Engine: Allison V-1710-63; E6
No built: 210

P-39L
Engine: Allison V-1710-63, 1325 hp
Wingspan: 34 ft 0 in / 10.37 m
Length: 30 ft 2 in / 9.2 m
Height: 11 ft 10 in / 3.63 m
Empty weight: 5600 lb / 2540 kg
Loaded weight: 7780 lb / 3530 kg
Max speed: 380 mph / 612 kph
ROC: 4000 fpm / 1220 m/min
Service ceiling: 35,000 ft / 10,670 m
Ferry range drop tank 160mph/256kph: 1475 mi / 2360 km
Armament: 1 x 37mm cannon. 30rds / 2 x 0.5in Browning-Colt / 2 or 4 x 0.30in mg
No built: 250
Like P-39K, but with wider Curtiss prop

P-39M
Engine: 1 x Allison V-1710-83, 1,200hp.
Length: 30.15ft (9.19m)
Width: 33.99ft (10.36m)
Height: 11.84ft (3.61m)
Empty Weight: 5,611lbs (2,545kg)
Maximum Take-Off Weight: 8,400lbs (3,810kg)
Maximum Speed: 386mph (621kmh; 335kts)
Maximum Range: 650miles (1,046km)
Rate-of-Climb: 3,333ft/min (1,016m/min)
Service Ceiling: 35,991ft (10,970m)
Armament: 1 x 37mm Oldsmobile cannon with 34 rounds OR 1 x 20mm Hispano-Suiza cannon.
2 x 12.7mm machine guns upper forward fuselage with 200 rounds each.
4 x 7.62mm machine guns in wings (2 to a wing) with 1,000 rounds each.
Bombload: 1 x 500lb
Accommodation: 1
Hardpoints: 1
No built: 240

P-39N Airacobra
Engine: 1 x Allison V-1710-85, 895 kW (1,200hp).
Span: 10.36m (34ft).
Length: 9.19m (30 ft 2in).
Height: 3.8 m / 12 ft 6 in
Wing area: 19.8 sq.m / 213.13 sq ft
Ceiling: 10670 m / 35000 ft
Max T/O weight: 3720kg (8,2001b).
Empty weight: 2560 kg / 5644 lb
Max speed: 399 mph at 9,700 ft.
Operational range: 750 miles.
Armament: 1 x 37-mm cannon, 2 x 12.7-mm (0.5-in) mg and 4 x 7.62-mm (0.3-in) mg plus provision for 1×227-kg (500-lb) bomb carried under the fuselage.
No built: 2095
V-1710-85 engine, other changes

P-39Q
Engine: Allison V-1710-85, 1200 hp
Wingspan: 34 ft
Wing area: 213 sq.ft
Length: 30 ft 2 in
Empty weight: 5968 lb
Loaded weight: 8052 lb
Max speed: 385 mph
Cruise: 240 mph
Max range: 675 mi
Armament: 4 x 12.7-mm/0.5-in mg.
No built: 4905

P-45A Kobrushka
Engine: Allison V-1710-47, 1375 hp at sea level, 1,325 hp at 15,500 ft
Wingspan: 34 ft 0 in
Length: 32 ft 7 in
Height: 12 ft 5 in
Wing area: 223 sq.ft
Empty weights: 5847 lb
Normal loaded weight: 7900 lb
Maximum loaded weight: 8500 lb
Maximum speed: 330 mph at 5000 ft, 367 mph at 10,000 ft, 386 mph at 21,000 ft
Climb to 5000 ft: 1.5 min
Climb to 20,000 ft: 6.5 min
Maximum range (clean): 425 miles at 20,000 feet at 270 mph
Range one 145.7 Imp gal drop tank at 196 mph: 1025 miles
Service ceiling: 37,500 ft
Armament: 1x 20mm M2 cannon and 4 x .50 machine guns

P-45B Kobrushka
Engine: Allison V-1710-47, 1375 hp at sea level, 1,325 hp at 15,500 ft
Wingspan: 34 ft 0 in
Length: 32 ft 7 in
Height: 12 ft 5 in
Wing area: 223 sq.ft
Empty weights: 5847 lb
Normal loaded weight: 7900 lb
Maximum loaded weight: 8500 lb
Maximum speed: 330 mph at 5000 ft, 367 mph at 10,000 ft, 386 mph at 21,000 ft
Climb to 5000 ft: 1.5 min
Climb to 20,000 ft: 6.5 min
Maximum range (clean): 425 miles at 20,000 feet at 270 mph
Range one 145.7 Imp gal drop tank at 196 mph: 1025 miles
Service ceiling: 37,500 ft
Armament: 1x 20mm M2 cannon and 4 x .50 machine guns