The Polikarpov I-152 or I-15bis was the second in the series of biplanes that began with the I-15 and ended with the I-153, and in some ways was a step backwards from the earlier aircraft. One of the most distinctive features of the I-15 had been its upper gull wing, which had no centre section and instead emerged from the top of the fuselage. This reduced wing loading and thus increased manoeuvrability, but was not universally popular. After some debate Polikarpov was ordered to produce a new version of the aircraft with a standard straight upper wing.
Although this aircraft is generally known as the I-152, it's official designation for much of its life was probably the I-15bis, with the I-152 designation reserved for a further improved version that was instead replaced by the I-153. Here we will use the generally accepted name.
The first precursor of the I-152 was a single modified I-15 produced in the spring of 1935 at Zavod 39. This eliminated the upper gull wing, replacing it with a more conventional straight wing. The changes increased the weight and the wing loading of the aircraft, and tests in May-July 1935 proved that its performance suffered. Top speed was down to 193mph at sea level and 223mph at 10,000ft. Climb rate, turning time and general manoeuvrability also fell.
The poor performance of this prototype meant that a more significant redesign would be needed before a straight wing I-15 could enter production. This new fighter, the TsKB-3bis was designed during 1936, and underwent acceptance trials in July 1937. It was generally similar to the I-15, but with the new central wing section. It was significantly heavier than the older aircraft, and had a slower rate of climb and reduced manoeuvrability. The prototype failed its acceptance trials, but despite this was still ordered into production.
Production began at Zavod No.1 in Moscow in the middle of 1937, but didn't reach full speed until 1938. Early aircraft used the same M-25 engine as later I-15s, a licence built version of the Wright Cyclone. This was replaced in mid-1938 by the M-25V, which improved its performance at altitude. Fuel capacity was also improved during the production run. The I-152 had a NACA cowl, replacing the narrower Townend ring used on the I-15. The I-152 was armed with four PV-1 7.62mm machines carried around the engine, and could carry two bomb racks under the wings. These could also be used to carry extra fuel tanks or replaced with racks to carry the RS-82 unguided air-to-ground rocket.
A total of 2,408 I-152s were produced, starting in the autumn of 1937 and ending in 1939. This made it the second most numerous member of the I-15 family, behind the I-153 of which 3,437 were built.
In July 1937 Japan invaded China, beginning the Second Sino-Japniese War. On 21 August 1937 China and the USSR signed a Non-Aggression Pact, which included secret clauses in which the Soviet Union promised to provide military assistance to China. One of the first results of this was the dispatch of four 'volunteer' fighter squadrons to China, originally all equipped with the I-152, a theoretical total of 124 aircraft although only 115 appear to have been deployed.
At this point the Japanese Army was still operating the Kawasaki Ki-10 Army Type 95 Model 1, a biplane fighter. The I-152 was faster than the Ki-10 up to 11,483ft, had a better rate of climb and was better armed. The Japanese began to suffer heavy casualties, and rushed the Mitsubishi A5M2a Navy Type 96 Carrier Fighter aircraft into combat. This was a more even match - the Japanese monoplane was faster than the I-152, but was less manoeuvrable and less heavily armed. The I-152 held its own against the A5M2.
In January 1938 two of the four I-152 squadrons were replaced by squadrons operating the Polikarpov I-16 monoplane.
A total 186 I-152s were supplied to the Chinese Air Force, 93 late in 1937 and another 93 in the first third of 1938. Training was poor, and generally so were combat results - the worst day perhaps came on 15 April 1939 when a force of thirty Chinese I-152s engaged a Japanese force with twelve Ki-10 biplanes and three newer Nakajima K-27 Army Type 97 Fighter monoplanes. The Japanese claimed to have shot down 24 of the 30 Chinese aircraft.
The biggest battle of the air war came on 29 April 1938 over Wuhan and involved four Soviet squadrons and two Chinese squadrons, with 67 I-152s and I-16 fighters against a force of 18 G3M bombers and 27 (or 39) fighters. This time the combat was more even. The Chinese admitted to nine losses, the Soviets to two. In return the Chinese claimed to have destroyed ten Japanese bombers and eleven fighters, while the Soviets claimed that 36 out of 39 Japanese fighters had been destroyed.
The I-152 and I-16 were still in use with the Chinese Air Force when the war with Japan resumed in 1939. At first they held their own, but on 13 September 1940 the Mitsubishi A6M1 Zero made its combat debut. After this the older Soviet aircraft were very badly outclassed.
Khalkhin Gol River Incident
The I-152 was involved in the direct clash between Japan and the Soviet Union on the border between Manchukuo and Mongolia, where a series of skirmishes along the Khalkhin-Gol River erupted into a full-scale war on 11 May 1939. One fighter regiment of I-152s was involved from the start, and another arrived during the battle, fighting alongside three equipped with the I-16 monoplane. The Japanese were now almost entirely equipped with the Nakajima Type 97 monoplane.
The fighting over Mongolia demonstrated the problems with the Soviet doctrine of two types of fighters. The 'fast' I-16 was actually slower than the Ki-27, so was unable to break up the massive Soviet formations. When huge dog fights did develop the Japanese were able to use their superior speed to escape from any dogfight with the slower I-152s.
Both sides made massively inflated claims at the time. The Japanese claimed to have destroyed 1,260 aircraft, while the Soviets claimed 590 aerial victories and 55 aircraft destroyed on the ground. In return the Japanese admitted to 154 aircraft lost or damaged and the Soviets to 207. To put these figures into some context both sides committed around 500 aircraft to the fighting! The fighting had proved that the I-152 was no longer an effective front-line fighter, and had forced the Soviets to introduce the new I-153 into combat in very small numbers.
Although direct Soviet involvement in the Spanish Civil War was over by the end of 1938 Stalin approved the delivery of three batches of I-152s in response to a request for assistance from the Commander-in-Chief of the Republican Air Force. Of these 93 aircraft one batch of 31 reached Spain, and in January 1939 was formed into three squadrons of nine aircraft. Sadly these aircraft arrived too late to have any impact on the fighting. They weren't involved I any clashes with Nationalist aircraft, and suffered no combat losses. Two were lost in accidents and the remaining 29 escaped to France. Twenty of these aircraft were later returned to Spain, where they remained in front line use until the mid 1940s, and were used for secondary duties until 1954.
Second World War
A massive number of I-152s were still in front line service in the Red Air Force on 22 June 1941 at the start of the German invasion of the Soviet Union. Many were allocated to units close to the new front line, and hundreds were destroyed in the initial attacks. Despite being outclassed by the German fighters, the surviving I-152s had to remain in front line service until more modern Soviet fighters were available to replace them in 1942. The surviving aircraft were then used as ground attack aircraft and as night bombers, suffering heavy losses when they were caught by the Germans. The I-152 remained in use in these later roles into 1943.
The I-152TK was a prototype for a version of the aircraft equipped with two TK-3 turbosuperchargers. The extra 308lb weight of the superchargers cancelled out the boost from the superchargers, and the venture ended after a series of test flights in 1939.
I-152DM Dopolnitelny Motor (auxiliary motor)
The I-152DM was given two Merkulov DM-2 ramjets in an attempt to improve performance. Tests began in December 1939, and between then and June 1940 a total of 54 successful flights were made. The ramjets increased top speed by 11-13mph when in use, but reduced speed by at least this much in standard flight.
The I-152 DIT-2 was a two-seat trainer version of the aircraft, with a second cockpit with dual controls in front of the normal cockpit. Weight was saved by removing armour, two machine guns and reducing the ammo available for the remaining guns. The DIT-2 underwent tests in 1939 and was considered to by unacceptably prone to spinning to be used as a standard trainer. It was approved for use with more experienced pilots as a conversion trainer.
Engine: Shvetsov M-25V
Wing span: 33ft 5.5in
Length: 20ft 7in
Height: 9ft 8in
Empty Weight: 2,888lb
Maximum Weight: 4,044lb
Max Speed: 226mph
Service Ceiling: 31,165ft
Range: 497 miles
Armament: Four 7.62mm machine guns
Bomb-load: Two 110lb four 44lb or eight 22lb bombs or two 21 gallon fuel tanks; racks could be replace with Type RO rocket rails for RS-82 unguided air-to-ground rocket