High-Altitude Reconnaissance Bomber
Il-4TK (High-altitude reconnaissance bomber) On March 16, 1943 test pilot V.K. a cruising altitude of 11,000 m. Such a high cruising altitude for that time was ensured by the use of TK-3 turbochargers developed at CIAM on the aircraft. Thanks to the presence of turbochargers, the power of each M-88B engine at an altitude of 11,000 m was supposed to double and become equal to 644 ... 647 kW (875 ... 880 hp).
The placement of turbochargers on the aircraft was determined by the desire of the designers to ensure the maximum fire safety of the aircraft. In this regard, the turbochargers were installed not near the engine exhaust manifolds, as has always been done, but at the very end of the engine nacelles under the wing of the aircraft, far from the fuel tanks. The turbochargers did not have the usual horizontal, but the vertical arrangement of the rotor axis. The turbochargers began to work when the pilot closed the bypass damper, which directs the exhaust gases of the M-88B engines from the exhaust manifold to the pipelines laid along the sides of both engine nacelles in troughs with fire protection. From the pipeline, exhaust gases entered the turbine blades of the turbocharger, forcing it and the associated centrifugal supercharger to rotate at a frequency of 23,000 rpm, which was supposed to provide external air supply to the carburetor of the M-88B engine with a flow rate of 0.74 kg/s. Outside air entered the centrifugal supercharger through a suction pipe located on the upper surface of the engine nacelle.
Another feature of the Il-4TK aircraft was a sealed ventilation-type cockpit for the pilot and navigator, with the pilot sitting in front and the navigator in the back. The cockpit was designed for an overpressure of 0.04 MPa (0.4 kgf/cm²), which determined the characteristic external feature of the aircraft - the spherical shape of the nose of its fuselage. The cabin was pressurized with air taken from the TK-3, which was filtered before entering the cabin. The pressure in the pressurized cabin was regulated by a system of valves, and the air temperature in it was maintained at the required level by an air-to-air radiator.
The aircraft did not have defensive small arms, but an AFA-3 aerial camera with remote control from the cockpit was also installed in the tail section of the aircraft fuselage. To monitor the operation of the propeller-driven group and to take its characteristics, additional equipment and control and recording equipment were mounted on board the aircraft. The flight weight of the Il-4TK aircraft was 10 593 kg.
High-altitude flights of the aircraft showed a discrepancy between the calculated characteristics of the TK-3 and the practical data obtained in flights up to an altitude of 9300 m. In addition, the VISH-61IF propellers did not provide the aircraft with the required rate of climb. In this regard, it was planned to install improved TK-M turbochargers and new AV-9F high-altitude propellers on the Il-4TK aircraft. But these works were never completed. In the context of the strategic air superiority won in 1943 by Soviet aviation, conventional Il-4 aircraft, accompanied by fighters, successfully coped with the combat missions assigned to them, and further work to improve the Il-4TK aircraft was considered inexpedient. The experience of the creation and flight tests of the aircraft was used in the further work of the design team.