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. Cynics have pointed to the P-45 Kobrushka as a unique example of a bureaucracy admitting it was wrong. This has an element of truth to it but no more than that. 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.
Bell P-45A Kobrushka
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
Specifications of the P-45A
One Allison V-1710-47 engine rated at 1375 hp at sea level and 1,325 hp at 15,500 feet. Maximum speed 330 mph at 5000 feet, 367 mph at 10,000 feet, 386 mph at 21,000 feet. Climb to 5000 feet in 1.5 minutes. Climb to 20,000 feet in 6.5 minutes. Maximum range (clean) was 425 miles at 20,000 feet at 270 mph. With one 145.7 Imp gal drop tank, range was 1025 miles at 196 mph. Service ceiling was 37,500 feet. Weights were 5847 pounds empty, 7900 pounds normal loaded, 8500 pounds maximum loaded. Dimensions: Wingspan 34 feet 0 inches, length 32 feet 7 inches, height 12 feet 5 inches, wing area 223 square feet. Armament, 1 20mm M2 cannon and four .50 machine guns
Bell P-45B Kobrushka
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.
Bell P-45C Kobrushka
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.
Bell P-45D Kobrushka
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.