Aviation of World War II
An escort fighter attacks an enemy that is trying to break through to the bombers it is escorting. The escort aircraft is incapable of attacking, it only supports the bombers flying nearby with fire, representing in essence a mobile firing point. Nevertheless, we could not ignore such unusual aircraft, designed primarily to destroy the air enemy.
In our country, A.N. Tupolev began to develop a similar concept, in the early 30s he created the R-6 aircraft. Then such a machine was called a "cruiser", and the squadrons armed with them were called cruising. The "cruiser" was supposed to have the speed and range of a bomber, but due to the lack of bomb armament, it was equipped with much more powerful small arms and was supplied with a large ammunition supply. Maneuvering combat was not envisaged on it. The "cruisers" were supposed to fringe the line of heavy bombers, protecting them beyond the range of their fighters.
R-6 and its modernized version KR-6 survived until the second half of the 30s, but by this time they were already outdated. They could not even keep up with the latest modifications of the TB-3 - aircraft that were not so fast for that time. When new DB-3 high-speed bombers began to enter the armament of the Red Army Air Force, the problem of covering them in long-range raids arose again. To escort the DB-3, an aircraft with no less speed and range than its own was needed. It was natural to create a machine based on the DB-3.
This is how the TsKB-54 project appeared. It was developed in OKB-39 under the leadership of S.V. Ilyushin. The standard serial DB-3 (TsKB-30) was taken as the basis. All bomb weapons have been removed. But the rifle was significantly strengthened. On an ordinary DB-3, there were three ShKAS machine guns: one in the bow mount of the NU, one in the upper SU, and one more in the lower (hatch) LU. Usually the latter was criticized, which was distinguished by a narrow sector of fire and poor visibility. In addition, the SU and LU were serviced by the same crew member - the gunner-radio operator. To get to the hatch gun, he had to go down, and all this time he did not see anything at all.
At TsKB-54, the standard LU was supplemented with a second ShKAS. It was mounted under the fuselage in a cigar-shaped gondola that rotated on a hinge. The machine gun could deviate up and down and spin 240 °. The gondola with a machine gun, obeying the shooter, who remotely controlled it from the fuselage, shot through a significant part of the space under the aircraft. The drive of the ventral installation was electromechanical. The shooter aimed through a converted OPB-1 bombsight, which worked like a periscope. The ammunition of this installation consisted of 300 rounds.
The bow and top mounts were replaced with cannon mounts. The guns allowed not only to increase the power of the volley, but also to open effective fire from a greater distance. A 20-mm ShVAK cannon with 120 rounds was mounted in the bow mount. Instead of the SU, they put another turret with the same ShVAK gun, but with a reserve of 240 rounds. The new tower was significantly larger than the SU, it had only one configuration - marching and combat at the same time. SU had two provisions. In the marching one, it did not protrude from the contours of the fuselage, in the combat one, its top was raised, and the gap was covered with an "accordion" made of rubberized fabric. In the new turret, the gun stood somewhat asymmetrically, with a shift to the port side.
ShVAK with its long barrel at high speeds created significantly more resistance, so an aerodynamic compensator appeared on the turret cap. To service all these weapons, the crew of the aircraft had to be increased by adding one more person. On the DB-3, the crew consisted of a pilot, a navigator and a gunner-radio operator. Now they turned on another gunner-operator of the ventral gondola.
For conversion into a prototype TsKB-54, one of the first DB-3s, produced by plant No. 18 in Voronezh, was singled out. The refinement was carried out by the workshop of plant No. 39 in Moscow, on which the Ilyushin Design Bureau was based. The machine had M-85 motors, constant pitch propellers and an early type chassis with a pneumohydraulic cleaning mechanism. All this was preserved on the experimental TsKB-54.
In fact, they first of all wanted to test new weapons on this aircraft. The experimental TsKB-54 was ready at the beginning of 1938. After short factory tests conducted by V.K. Kokkinaki, the car was transferred to the Air Force Research Institute. The plane was there from March to May 1938. Both at the plant and at the TsKB-54 Research Institute, it flew mainly on skis. Since the skis of the early series DB-3 were not retracted in flight (in winter, the struts were locked in the extended position), the flight data of the escort aircraft did not differ in particular expressiveness. And the combination of the M-85 with the old TsKB-26 propeller in 1938 was already obsolete; at the factories, more powerful M-86s with TsKB-30 propellers were installed on the new DB-3.
The testing of TsKB-54 weapons seemed much more important. Not everyone is rated equally. The upper turret installation proved to be the best, it was much less convenient to use the bow point, and the remotely controlled ShKAS in the rotary gondola was rejected. His field of fire was indeed very large, but under the fuselage the gondola created great resistance and, with sudden movements, provoked the buildup of the aircraft.
Taking into account the shortcomings of the first version of TsKB-54, in 1939 a second one was created. This time, a more modern bomber manufactured at the end of 1938 was taken as the basis. The car was redesigned from the 16th series of plant No. 39. This series was transitional to the DB-ZB modification. The plane was powered by M-87A engines and VISH-3 variable pitch propellers. The cockpit canopy was of a new, wider type. All glazing was now plexiglass instead of celluloid.
The set of small arms was different from the first version. The ventral gondola was removed, replaced by a pair of blisters on the sides. In each blister, a ShKAS machine gun with a supply of 260 rounds stood on the pivot. In these on-board installations, parts of a standard LU were partially used. They also wanted to keep the latter, but they did not install it on an experimental machine.
Cannon mounts have also been improved. They received new PPU sights. The nose cannon ammunition was increased to 220 rounds. The mechanism of the bow turret was somewhat changed, the shell box was redesigned. All of its glazing was now plexiglass. Spent cartridges were not collected in a cartridge case, as before, but were thrown overboard.
The top tower has also undergone changes. The turning mechanism was improved, the frame of the cap was redesigned, now also glazed with plexiglass. Improved aerodynamic compensator.
In this form, TsKB-54 was re-released first for factory, and then for state tests. The strengthening of small arms led to the fact that the escort aircraft turned out to be 100 kg heavier than the base bomber. Flying on a wheeled chassis at an altitude of 4000 m, TsKB-54 was inferior in speed to the serial DB-3 of plant No. 18 with the same power plant 7 km / h, and the machine manufactured by plant No. 39 - 16 km / h. This meant that the escort plane was unable to keep up with the bombers it was supposed to protect. Weight gain brought work to a standstill. As a result, the serial production of TsKB-54 was abandoned.
Only a cannon tower was tried to be introduced into the series. On the act of approving the report of the Air Force Research Institute on state testing of the second version of the escort aircraft, you can see the resolution of the then head of the Air Force of the Red Army Loktionov: ". However, this resolution had no consequences. Serial DB-3s still retained purely machine-gun armament, apparently due to the fear of overweighting the aircraft and lowering its flight performance.
It must be said that attempts to implement the concept of such an escort aircraft based on a bomber with enhanced defensive weapons abroad also proved unsuccessful, and for the same reason. Each time it turned out that the "cruiser" was heavier than the original bomber. The Japanese G6M1 (based on Mitsubishi's G4M1) and the American YB-40 (converted from the Flying Fortress B-17) reached the stage of small series. Both of them, due to the increase in flight weight, lagged behind their prototypes, proved to be ineffective in combat operations and quickly left the stage.