Bereznyak-Isayev BI-1 - Return To Moscow, Isaev's Engine

Return To Moscow, Isaev's Engine

In May 1943, OKB-293 returned from its evacuation and set up operation in Khimki, a suburb of Moscow. On May 18, Bolkhovitinov wrote a detailed report "On Rocket Aircraft and Further Prospects". He emphasized the need to study the dangerous regime of "shock stall", and to safely transition through transonic speed and beyond. He proposed the goal of a new rocket plane capable of 2000 km/h.

The next year, Bolkhovitinov had five more aircraft produced, BI-5 through BI-9. In the Spring of 1944, BI-6 was fitted with a pair of Igor A. Merkulov's DM-4 ramjet engines. It did not contain a rocket engine, so it was towed into the air. The pilot, Boris Kudrin, flew the BI-6 three times, but was never able to get both ramjets to start at the same time. The plane was taken to TsAGI for further tests in the T-101 wind tunnel. The DM-4 auxiliary motor was also tested on the YaK-7b fighter.

With the loss of the D-1-A-1100 engine, Isaev began designing a new engine. The RD-1 was completed and tested in October 1944. The general form of the engine was the same as Dushkin's, but with numerous improvements. Isaev fashioned the sections from 12Kh13 stainless chromium steel (13% chromium, 0.12% carbon content). The head had 85 swirling injectors arranged in a honeycomb pattern that promoted improved fuel-oxidizer mixture. It also used a more reliable electric arc starter instead of a glow plug. Isaev also improved the regenerative cooling, increasing the flow rate around the nozzle.

BI-7 was flown twice with the RD-1 engine, on January 24 and March 9 1945. Pallo reports there was an emergency with the landing gear during the January flight. In addition to the new engine, various changes were made to the plane's design: a larger rudder, smaller false keel, and different wing fillets. During the test flights, the pilot Boris Kudrin, noticed some tailfin flutter. On May 29, the pilot M.K. Baykalov tested the BI-7 in glider mode, without starting the engine, and the flutter was not detected. At this point, the plane was too corroded by nitric acid to fly again, and it was retired. To further investigate the flutter problem, BI-5 was modified in the same fashion as BI-7 (but with no engine) and tested in glider flights; however, the problem was not reproduced.

After BI-6 was sent to TsAGI, BI-9 was put into service as a replacement (marked with a "6" on its tail). Flown by Boris Kudrin and M.A. Baikalov, it was used in glider tests with extra payload weight. The fate of BI-8 is unknown.