The IP-3 fighter, which received the manufacturing name DG-53 (Russian: Григорович ИП-3 (ДГ-53)), basically differed from the DG-52 (IP-1) due to its smaller dimensions, its reduced surfaces and its lower flight weight. It seems that with the IP-3 Grigorovich tried to obtain a fighter for close combat armed with machine guns, but for some reason he drifted towards a utility model equipped with Kurchevski ‘s dynamoreactive cannons. In this case, the cannons were simply smaller in terms of caliber, weight and dimensions.
Grigorovich IP-3 / DG-53 Article
The IP-3 fighter was designed to use the 37 mm APK-11 recoilless automatic cannon, proposed by Kurchevski in 1932. These cannons stood out for their magazine feeding, which allowed the number of projectiles per gun to be increased to 25. Up to 12 projectiles were placed in two magazines and the last one was placed directly in the gun when preparing it. The weight of the APK-11 with the magazines reached 39.1 kg. The explosive projectile weighed between 475 and 500 grams and was ejected from the barrel at a speed of 438-475 m/s. The reloading of the barrel after each shot was done automatically using compressed air located in a 5-liter tank.
In addition to its smaller dimensions, the IP-3 was easily differentiated by having individual exhaust pipes that came out of holes in the hood and the introduction of cantilever wing planes. A novelty in this model was the installation of landing flaps. The Shvetsov M-25 radial engine, developed on the North American Wright Cyclone, remained as the power plant.
This fighter was designed to carry two 37mm Kurchevski APK-11 cannons as well as two light machine guns. Unfortunately, at the time of finishing its construction, the APK-11 guns were not yet available. By the end of 1934 it was decided that the APK-11 guns were not ready and for their acceptance it would be necessary to modify them.
On July 2, 1935 the head of the OKB of Factory No.1 Aviajim DP Grigorovich informed the head of the GUAP GN Korolyov about the completion of work on the prototype. In his letter he wrote:
“The IP-3 aircraft with Wright Cyclone is ready for factory tests and has been received by the LIS of Factory No.1 to carry out the tests. I request your approval to start them.”
Factory tests were started in July 1935. Apparently the hope of receiving the APK-11 guns remained latent and the definition of the future of the plane depended on these works.
With the decision to suspend work on the dynamoreactive guns, the interest in the IP-3 disappeared and the development of the model was not continued. In later documents appears the instruction to delete the IP-3 Shvetsov M-25 of Factory No.1 from the construction plan for 1937.
A second prototype known as the IP-4 or DG-53bis and designed to carry two ShVAK guns instead of the Kurchevski ones, remained in the project phase.
Kurchevsky continued to improve his 37mm guns and even managed to get it approved for mass production, but this weapon never found practical application.
IP-3
Engine: Shvetsov M-25, 700 hp
Wingspan: 9.60m
Length: 7.08m
Wing area: 16.36 m²
Normal takeoff weight: 1548 kg
Maximum speed at sea level: 382 km/h
Maximum speed at height: 435 km/h
Cruising speed: 298km/h
Practical range: 830 km
Practical ceiling: 8800 m
Armament: Two 37mm Kurchevski APK-11 cannons, 25 rds & two 7.62mm ShKAS machine guns.
Accommodation: 1
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