Bereznyak-Isayev BI-1 - Test Flights in The Urals

Test Flights in The Urals

In October, both OKB-293 and RNII were evacuated to the Urals, along with most of Moscow's war industry. Bolkhovitinov's team was stationed in Bilimbay, and Dushkin's team in Sverdlovsk, about 60 km away. A test stand was built on the shore of frozen lake Bilimbay, with a dynamometer cradle to hold the BI-1 during engine testing. A new test pilot, Grigory Yakovlevich Bakhchivandzhi, was assigned to the team. Dushkin was increasingly absorbed by other work, including RNII's own rocket plane project, the Kostikov-302. He assigned his engineer Arvid V. Pallo to oversee the installation and testing of the rocket engine.

Nitric acid presented a constant problem, corroding parts and causing skin burns and respiratory irritation. Tanks of sodium carbonate solution were kept around to neutralize acid spills. On February 20 1942, the engine exploded during a full system test. The nozzle section was blasted into the lake, and the engine head struck the back of the pilot's seat, knocking Bakhchivandzhi against the instrument panel and injuring him slightly. From a broken propellant line, pressurized nitric acid drenched Pallo. Fortunately, quick thinking mechanics dunked him head-first into a tank of soda solution. His face was yellow from the characteristic acid staining, but his glasses saved him from being blinded. To protect the pilot in the future, a 5.5 mm steel plate was added to the back of the seat.

By April 1942, BI-1 was ready for testing at nearby Koltsove airfield. A test commission was formed, with representatives from OKB-293, RNII and the airforce research lab (NII VVS). On May 2, the pilot let the plane lift off one meter under low thrust.

On May 15, at 19:02 (UTC), Bakhchivandzhi made the first real flight of BI-1, reaching an altitude of 840 meters and a maximum speed of 400 km/h. The mass of the plane had been reduced to 1300 kg (only 240 kg of nitric acid and 60 kg of kerosene loaded), and the engine was operated under a thrust of only 500 kgf. The pilot shut the rocket engine off after about one minute, when a light indicated it was overheating. Landing, the aircraft descended too rapidly because of insufficient forward speed, and the landing gear broke on touchdown. The pilot was unhurt and reported that, aside from the rough landing, the plane handled well. The flight lasted only 3 minutes and 9 seconds.

In July, Dushkin recalled Pallo to help work on the "302" rocket-plane project. Bolkovitinov asked Isaev to take over and master the technology of liquid fuel rocket engines. Isaev got permission to visit Valentin Glushko, the leading Soviet expert on rocket engines, who was then working in a special lab for political prisoners. Glushko taught Isaev the complex techniques of chamber-wall heat transfer calculation and engine design, developed by himself and Fridrikh Tsander in the early 1930s. Isaev's propellant feed system was simple, but it produced an uneven fuel pressure that diminished as compressed air was used up. Bolkovitinov and his engineers wrestled with this problem, designing pressure regulators and even a piston fuel pump driven by compressed air, but none of these improvements were realized.

Too damaged by acid to fly safely, BI-1 was retired and the second prototype BI-2 was made ready. Backchivadzhi made the second flight on Jan 10, 1943, reaching 1100 meters but with the engine still throttled back for a maximum speed of 400 km/h. The first flight had been with landing gear kept down, and some vibration has been observed. This time, the flight was made with landing gear stowed, and no vibration was observed at the cautious speed.

The third flight was made on Jan 12 (some sources say Feb 10) by a temporary test pilot, Konstantin Gruzdev, while Backchivadzhi was consulting on Kostikov's "302" project. This time the engine was opened up to full thrust of 1100 kgf and a speed of 675 km/h was achieved and a maximum altitude of 2190 meters. During the winter, the landing gear was switched from wheels to skis. On Gruzdev's flight, one ski broke off during take-off, but he was able to land safely. Backchivandzhi returned to make flights in the third test plane BI-3 on March 11, 14 and 21. He reached a maximum altitude of 4000 meters with a maximum rate of climb of 83 meters per second.

The March 21 flight was with a full load of ammunition. Most of the BI models did not contain an actual pair of anti-aircraft cannons, and some reports claim that BI-4 was used for the live ammunition tests. The guns were never fired in any flight. The BI-4 model was reportedly used as the template for the mass production of 30 to 50 BI-VS model aircraft by Andrey Moskalev's factory. Moskalev augmented the twin ShVAK guns with a load of ten thermite bombs.

On March 27, during a low-altitude test flight, Backchivandzhi pushed the aircraft's speed. After 78 seconds, the plane went into a 45-degree dive and crashed into the ground, killing the beloved pilot. The accident put a halt to flight tests, and a lengthy investigation began. Eventually, after wind tunnel testing, it was determined that the BI-1 lost control due to the effects of transonic velocity. Estimates of Backchivandzhi's final velocity range from 800 to 990 km/h, but the recording instruments were too damaged by the crash for a reliable measurement. March 27 is considered a black day in Soviet aviation history, also being the date that Yuri Gagarin died in a jet plane crash. In 1973, Backchivadzhi was posthumously awarded Hero of the Soviet Union.