Bereznyak-Isayev BI-1 - War-time Development

War-time Development

On June 21, Isaev proposed a new design using compressed air instead of a pump to force propellant to the engine. The next day, Operation Barbarossa brought the Soviet Union into World War II, and the rocket-powered interceptor suddenly became important. Bereznyak and Isaev began a new more detailed design, which they finished in three weeks. On July 9, Bolkhovitinov and his project-G team met with Andrey Kostikov the head of RNII. Dushkin was not happy about the idea of bypassing his fuel pump design, but they backed the plan and cosigned a letter that was eventually shown to Joseph Stalin. After giving a report at the Kremlin, they were ordered to build the plane and were given only 35 days to do so. The official order was dated August 1, but work began in late July. The engineers were given leave to visit their families, and then literally lived at the factory until the planes were finished.

The new design was called "BI" for Blizhnii Istrebitel (close-range fighter), but the letters were also understood by everyone to stand for its inventors: Bereznyak and Isaev. The original plan to include four machine guns was replaced by a design with a pair of 20 mm ShVAK cannons. The new plane was a low-wing monoplane 6.4 meters long, with a wingspan of 6.5 meters and an estimated take-off mass of 1650 kg (including 710 kg of propellant). Working around the clock, local furniture workers were employed to build the first two prototypes (BI-1 and BI-2). The skin was 2 mm plywood with a bonded covering of fabric. The Ailerons, elevators and rudder were fabric covered, and the flaps were duralumin. In the forward section were 5 compressed air tanks and 2 kerosene tanks. In the aft were 5 compressed air tanks and three nitric acid tanks. Pressurized to 60 atm, the tanks were made from a high-strength chromium-manganese-silicon steel ("Chromansil") that was not especially resistant to corrosion. Thus, the acid tanks had to be replaced periodically. Compressed air was also used to retract and deploy the landing gear and to power the anti-aircraft cannons.

On September 1, 1941, BI-1 was completed and ready for glider tests by pilot Boris N. Kudrin. Dushkin's engine was still not ready. A few weeks later, rival aircraft designer A.S. Yakovlev took it upon himself to tow the prototype to TsAGI for windtunnel testing. This alarmed Bolkhovitinov's team, because their patron had a rocky history with Yakovlev, but Alexander Sergeevich and aircraft designer Ilya Florov studied the test results and gave them sound advice for improvements. Yaw instability was corrected by enlarging the rudder and adding two circular plates to the tail horizontal stabilizer.