The Polikarpov I-3, a Soviet fighter aircraft, was developed in the late 1920s.
It was introduced into active service in 1929, but its operational lifespan came to an end in 1935 as more advanced fighters with superior capabilities emerged.
The development of the I-3 commenced in the middle of 1926, following the conclusion of investigations into the loss of the Polikarpov DI-1.
Despite sharing several characteristics with its predecessor, such as the staggered sesquiplane wing layout, the I-3 was an entirely new design.
The Aviation Trust’s OSS, under the guidance of Nikolai Nikolaevich Polikarpov, the department’s chief designer, undertook the task of creating this aircraft.
The choice of powerplant for the new fighter sparked extensive debate within the OSS.
Ultimately, Polikarpov dismissed the Wright Tornado radial engine and instead opted for the BMW VI liquid cooled V12 engine.
By April 1927, a wooden mock-up of the I-3 had been completed, but formal approval of the design was not granted until the 3rd June 1927.
Concurrently, in October, static tests were conducted on a full-sized model, coinciding with the finalisation of negotiations for a licence to use the BMW engine.
The I-3 aircraft featured an oval-section semi-monocoque fuselage that was covered with ‘shpon’, a type of moulded birch plywood.
The fuselage also included a small headrest that was smoothly integrated into its structure.
However, the engine was enclosed within a metal cowling for protection.
The wings of the I-3 were designed with a two-spar configuration and were covered with a combination of plywood and fabric.
These wings had a Clark Y profile and were reinforced with internal bracing wires to enhance their strength and stability.
The control surfaces of the aircraft were framed in duralumin, a lightweight aluminium alloy, but were covered with fabric.
The I-3 was equipped with differential Frise-type ailerons to ensure precise control during flight.
The wings were supported by duralumin N-type struts that had a teardrop profile and were further reinforced with steel bracing wires.
The aircraft was equipped with a conventional undercarriage that had fixed rubber shock absorbers, and the tailskid was constructed from duralumin.
Additionally, the main gear had the capability to be replaced with skis, similar to those found on the Polikarpov R-1.
The engine of the I-3 had a semi-retractable radiator that extended below the fuselage, positioned behind the rear main gear struts.
The aircraft was equipped with two fuel tanks, with the main tank located in the fuselage.
Additionally, a smaller 2.5-litre tank, primarily used for engine startup, was situated in the centre section of the upper wing, alongside the engine coolant tank.
The I-3 had a fuel capacity of 210 kg (460 lb).
In terms of armament, the initial configuration of the I-3 included two fixed 7.62 mm (0.300 in) synchronised Vickers machine guns.
However, these were later replaced by PV-1 machine guns.
The aircraft was equipped with a central OP-1 optical gunsight, which was complemented by a KP-5 ring sight offset to the starboard side.
Some variants of the I-3 were also equipped with bomb racks capable of carrying two 11.5 kg (25 lb) bombs.
The initial model of the aircraft was finished in the early months of 1928 and successfully took its inaugural flight on the 21st of February.
The manufacturer’s trials were concluded by the 10th of March, followed by the state acceptance trials on the 14th of April.
However, the pilots from the Air Force Scientific Test Institute (NII VVS) expressed concerns regarding the lack of stability in maintaining direction at high speeds, as well as a minor issue with the control response during manoeuvres.
To address these issues, modifications were made by increasing the surface area of the vertical tail and incorporating horn balances to the elevators, which helped alleviate the first problem.
Additionally, split ailerons were implemented to tackle the second problem.
It is worth noting that production had already commenced prior to the official approval for service use, resulting in the first forty aircraft being equipped with the smaller tailplane.
Subsequently, a second prototype was completed in August 1928, featuring a different propeller specifically optimised for high speeds.
This modification resulted in an increased top speed of 283 km/h (176 mph), albeit with a longer take-off run.
While the first 39 aircraft, along with the two prototypes, utilised imported engines, the remaining aircraft were equipped with domestically produced Mikulin M-17 engines.
In 1929, the Belorussian Military District received the initial deliveries of the I-3 aircraft, which replaced the Grigorovich I-2.
These new aircraft were assigned to various squadrons, such as the 4th and 7th Squadrons, later known as the 106th and 107th Fighter Squadrons respectively, stationed at Smolensk.
Additionally, the 13th and 5th Squadrons, later renamed the 108th and 7th Fighter Squadrons, were equipped with the I-3 at Bryansk.
The 9th Squadron, as well as the 17th and 19th Squadrons, which eventually transformed into the 116th and 117th Fighter Squadrons, also received these aircraft.
Furthermore, units based in Ukraine started receiving their I-3s the following year.
These included the 3rd Squadron, later known as the 109th Fighter Squadron, and the 73rd Air Detachment in Kiev, as well as the 91st Squadron, later renamed the 33rd Fighter Squadron, stationed at Bobruisk.
Additionally, the 1st, 2nd, and 3rd Schools of Military Pilots were among the recipients of these aircraft.
By October 1, 1930, a total of 252 I-3 aircraft were in service, which increased to 282 by the following year.
However, the number decreased to 297 by January 1, 1932, and further declined to 249 a year later.
Towards the end of 1933, the number of I-3s in service reached 239.
As newer and more powerful Polikarpov fighters, such as the I-5, I-15, and I-16, were introduced, the I-3 was gradually assigned to secondary roles starting in 1935. Variants Polikarpov D-2 The Polikarpov D-2 or DI-2 was a prototype of a two-seat fighter aircraft, which was derived from the single-seater I-3. Its notable distinctions included slightly larger dimensions and the incorporation of a second cabin equipped with armament. Unfortunately, the testing of its V-tail configuration concluded tragically with a fatal accident, ultimately resulting in the termination of its further development. Specifications Crew 2 Length 8.08 m (26 ft 6 in) Wingspan 11 m (36 ft 1 in) Wing area 27.85 m2 (299.8 sq ft) Airfoil Clark Y Empty weight 1,400 kg (3,086 lb) Gross weight 1,846 kg (4,070 lb) Powerplant 1 × BMW VI V-12 liquid-cooled piston engine, 545 kW (731 hp) Propellers 2-bladed fixed-pitch propeller Performance Maximum speed 278 km/h (173 mph, 150 kn) Range 585 km (364 mi, 316 nmi) Service ceiling 7,200 m (23,600 ft) Time to altitude 5,000 m (16,404 ft) 12 minutes 36 seconds Wing loading 66 kg/m2 (14 lb/sq ft) Power/mass 0.295 kW/kg (0.179 hp/lb) Horizontal turn time 14 sec Armament Guns 2 × 7.62 mm (0.3 in) PV-1 machine guns Sources King of Fighters – Nikolay Polikarpov and His Aircraft Designs – Vol 1 & 2. The Osprey Encyclopedia of Russian Aircraft 1875–1995-B Gunston. The History of Soviet Aircraft from 1918-Vaclav Nemecek.