In the spring of 1940 the TsAGI held a conference for aeronautical designers related to the use of reactive rockets and ramjets. The main engineer of the OKB-293 Victor Fiodorovich Boljovitinov was invited to this conference, who attended accompanied by two of his collaborators A. Ya. Bereznyak and AM Isayev. Bereznyak was the head of the mechanics brigade and Isayev was the chief of the engine brigade. The cause of this hasty conference was based on the confirmation that an intercept fighter with reactive power plant had begun to be developed in Germany which appeared in the last period of the War as the Messerschmitt Me-163.

In July the Council of People’s Commissars (SNK) launched the request for the development of high-speed stratospheric aircraft powered by jet engines. Bereznyak and Isayev were excited about the prospect of designing a jet-powered aircraft and, after receiving Bolkhovitinov’s approval, in the fall of 1940 they went to work on a project that was originally known as ” G “.

In 1940 they visited the Reactive Research Institute, where they learned about the work carried out by the engineer Leonid Estepanovich Dushkin on a reactive liquid fuel engine for the “302” fighter project that was then being developed at this institute.

The design of the ” G ” was designed primarily in plywood and duralumin, had a takeoff weight of only 1500 kg capable of reaching 800 km / h.

The Bereznyak and Isayev aircraft was initially designed to use a 1,400 kgf thrust engine with a fuel injection system into the ignition chamber. In order to simplify the process and decrease the creation time of the apparatus, on June 21, 1941 Isayev proposed to replace the pump injection system with a simpler injection system based on compressed air at 145-148 atmospheres from 115-liter cylinders. This made it possible to reduce the dimensions of the engine and improve its characteristics. This new engine was renamed D-1A (A corresponds to Azot (Nitrogen in Russian) and responds to the type of oxidant used in the combustion process). As a counterpart, the need to include large volume and weight oxygen cylinders in the engine resulted in the necessary decrease in the amount of fuel, so that the engine’s working time decreased to about two minutes.

The beginning of the Great Patriotic War led to a reassessment of the need. Bereznyak and Isayev worked tirelessly and in three weeks they had the preliminary project completed. A group of specialists asked Boljovitinov to issue a letter to motivate attention to the model. On 9 July of 1941 a letter signed by seven specialists were found among those who sent Bereznyak, Isayev, Dushkin, the factory director Boljovitinov and the principal engineer Kostikov. And a short time later a notification was received for them to appear at the Kremlin. The proposal was approved and AI Shaxurin together with AS Yakovlev presented a draft decree that was approved in August.

Bolkhovitinov was ordered in the short period of 35 days (instead of the three months requested by Bereznyak and Isayev ) to have a reactive powerplant interceptor fighter ready and the Research Institute 3 (NII-3) led by AG Kostikov to create the RDA-1-1100 reactive engine for this aircraft. On this basis the order of the National Committee (Narkomat) of the Aviation Industry (NKAP) was created.

The creation of the fuel tanks and the reactive engine power system based on the system developed by the NII-3 was introduced in the task of the KB of Bolkhovitinov and the task of KB Dushkin (as a member of the NII-3) was to guarantee constant engine operating speed between 400 and 1100 kg thrust in multi-launch regime.

The task was assigned on August 1, but the work started from the end of July. The OKB was declared “quartered” and worked without leaving the factory for a month and 10 days. On the first of September the first copy of the new aircraft was ready to be directed to tests at NKAP. The aircraft was built with virtually no finished detail plans, building many parts by eye. This was made easier by the small size of the aircraft.
The new design was named BI, short for Blizhny Istrebitel or Short Range Hunting, but many, even at that time, interpreted the initials as the initials of its creators.

The BI was designed as a single-seater monoplane with short wingspan (6.5 meters). The entire oval-shaped fuselage and monocoque structure, was constructed of wood and covered with 2 mm plywood covered with fabric.

The wing was integrally built and covered with plywood. The selected profile was TsAGI B-1-10 with a relative thickness of 12% and a trapezoidal plant. The ailerons, rudders and rudders were constructed of wood with textile coating, but the flaps were constructed of duralumin (on the BI-5 and BI-6 versions all control surfaces were made of duralumin).

The tail assembly incorporating a ventral fin and circular drifts at the ends of the outriggers. On the BI-1 the stabilizer was raised, but on later models it was released. The rudders were covered with fabric.

The project envisioned an armament of two 12.7mm Berezin machine guns and two 7.62mm ShKAS machine guns. These original plans were replaced by the installation of two ShVAK 20 mm cannons, providing for the possibility of their replacement in the series copies by two 23 mm cannons.

The retractable landing gear was fitted with wheels or skis. The main wheels had dimensions of 400 x 500 mm, while the skis were 1440 x 300 mm and featured a spring-loaded system. The main units were retracted towards the center line of the aircraft. The tail unit was located at the end of the ventral fin, being fixed but adjustable with dimensions 90x42mm. The retraction system was pneumatic.

The BI was powered by a 1,100 kg thrust Dushkin D-1A-1100 rocket engine. In the tail section there were five compressed air tanks and three tanks with nitric acid. These tanks, pressurized to 60 atmospheres, were constructed of a high resistance steel known as “Jromansil” consisting of an alloy of chromium, manganese and silicon with steel. Its fuel mixture of kerosene and nitric acid being not only dangerous to handle, but also causing corrosion of tanks and fuel lines. Despite its high hardness, this material was quite prone to corrosion, so the acid tanks had to be replaced periodically.

The compressed air from the tanks was also used to guarantee the retraction and deployment of the landing gear and for the firing of the cannons.

The pilot was located forward, in a cockpit with a transparent cover.

At the request of AS Yakovlev the glider of the BI fighter was tested in the wind tunnel of the TsAGI. This request considerably alarmed Bolkhovitinov’s team, aware of the harsh relations between their boss and Yakovlev. Despite this, the tests were carried out under the direction of GS Biushgens and AL Raij and after the results were completed, they were studied by Yakovlev himself and the aeronautical designer Ilya Florov, who suggested enlarging the rudder and adding two vertical fins in stabilizers to improve stability.

The first prototype, named BI-1, was only used as a glider without a motor towed by a Petlyakov Pe-2 to test the operating characteristics during landing. The first flight took place on 10 September 1941 piloted by Boris Nikolaevich Kudrin. During 15 flights it was possible to define all the main flight characteristics at low speeds. The tests showed that the behavior and the aerodynamic data corresponded with calculations.

The engine was not yet ready, mainly due to the complexities associated with technological innovation and the use of nitric acid. All safety measures needed to be observed to avoid toxicity, not only from the acid, but also from the vapors. There were even some cases of fire. Time constraints forced the autonomous testing of the engine to be skipped and went straight to testing it in the OKB test bed. The tests began in September 1941.

Before the evacuation, not much more could be done. On 16 October 1941 it was decided to evacuate the bureau and factory buildings of Boljovitinov to the Urals. The next day the engine test bed was dismantled and all documentation and materials were sent to the new location in Bilimbay, near Sverdlovsk (present-day Yekaterinburg). Also towards Sverdlovsk, about 60 km from the Bolkhovitinov location, on the 20th of the month the NII-3 with Dushkin was evacuated. The new test bed for the BI was installed on the shore of the frozen Lake Bilimbay.

Work continued at the new location. The pilot Kudrin fell ill and his position was taken by Gregory Yakovlev Bajchivandzhi. Dushkin at that time was immersed in the development of the powerplant for the new fighter developed under the direction of Kostikov himself and known as “302”, for which the engineer Arvid V. Pallo was appointed to supervise the engine works in the BI.

Nitric acid generated constant problems, corroding parts, causing skin burns and respiratory problems for mechanics. On 20 February 1942 during ignition of the engine in the test bed an explosion occurred. A jet of nitric acid was thrown at high pressure, hitting Engineer Pallo. The nozzle was thrown into the lake. The engine cover detached and flew off until it hit the pilot seat guard, loosening the mounting bolts. Bajchivandzhi was thrown forward, head banging on the instrument board. Only the quick action of the mechanics, who immediately put Pallo’s head in a container with soda and the use of glasses, prevented the accident from having further consequences. As a result of experience, a 5.5mm steel plate was installed at the rear of the pilot’s seat.

In March the test bed was repaired, and changes were made to the engine power system. Various hydraulic tests and 14 ignition tests were carried out on the engine destined to be located in the aircraft. On 25 April 1942 the aircraft was moved from Bilimbay to Koltsovo (to the Research Institute of the VVS ( NII VVS )) and 30 two starts were made to the engine and work began to prepare the BI for flight.

For the first flight of the BI a Government Commission was created with VS Pychnov. Included in the commission were Bolkhovitinov, the head of the NII VVS PI Fiodorov, the chief engineer of the BI project at the NII VVS, MI Tarakanovsky, the chief engine engineer AV Pallo. As chief pilot of the tests, G. Ya was appointed. Bajchivandzhi.

On May 2, the pilot, during a test run, lifted the BI slightly, to a height of about one meter, descending again due to low power.

The BI-1, with the 1,100 kg Dushkin D-1A rocket engine, took off for the first time on 15 May 1942 at 19:02 local time, with a flight of 3 minutes 9 seconds, the first in the world that was done with a interceptor rocket propulsion. For this flight, the takeoff weight was set at 1,300 kg and the engine was set to 800 kgf thrust. As a result, an altitude of 840 km / h was reached and a speed of 400 km / h. The ascent speed was 23 m / second. The pilot Bajchivandzhi would later write that unlike conventional airplanes the flying of the BI was extremely pleasant, highlighting the absence of the propeller and the noise and gases from its engine and highlighting the excellent view from the cockpit. A minor landing gear failure at the end of the historic flight hampered the development program, with the tail being damaged.

The results of the first tests were so promising that the commission decided to order the construction of a pre-series of 50 BI-VS for military tests at the AS Moscaliov construction facilities at Factory No. 499 located in the city of Zavodoukovsk. As a basis for development, the four BI-4 prototypes were taken, having as the main difference with the prototypes in addition to the two cannons in the fuselage, a closed bay with a cassette for bombs was installed in front of the pilot’s cabin. In this bay could be located 10 small 2.5 kg bombs designed to be dropped on bomber formations in the air.

Boljovitinov, very happy with the test results, asked to film the BI development process. With the recordings made, a documentary film was created that was named “Flight to the Future” (in Russian: “Полет в будущее”). This film was shown not only to personalities, but to KB and factory personnel. This led to a very tense situation with the NKVD and was on the verge of provoking the indictment of Bolkhovitinov for revealing military secrets.

Together with the decision to start serial production, the projects for the creation of training facilities in Sverdlovsk and Moscow were prepared, with the aim of preparing the pilots on the new aircraft. In 1943 it was expected to be able to create several units with the new fighter specialized in the interception of bombers.

The flight of the BI was fundamentally difficult due to the constant problems with nitric acid. On more than one occasion the acid leaked through the pipes or the walls of the tanks and the toxic gases also meant major problems that had to be constantly corrected, so the tests lasted throughout the winter of 1942 – 1943.

Due to the damage to BI-1 due to the corrosive action of nitric acid gases, the continuity of the program was carried out in the second, BI-2, and third, BI-3. These were built in the Factory No.293 in the winter of 1942 – 1943 and characterized by having a retractable landing gear with skis.

The second flight was performed with the BI-2, reaching an altitude of 1100 meters, but adjusted to not exceed 400 km / h. In this aircraft and in a short time, 4 flights were made, three by Bajchivandzhi (March 11, 14 and 21 1942) and another by KA Gruzdiev (January 12 1943). These flights reached a speed of 675 km / h (the calculated one was 1020 km / h at 10,000 meters), ascent speed of 82 m / s, flight ceiling of 4000 meters and flight time of 6 minutes and 2 seconds with 84 seconds engine working time. The flight of March 21 was carried out with the full load of ammunition. So far none of the prototypes had carried real weapons. There is evidence that the BI-4 was the prototype used to test the armament installation, although no firing tests were ever carried out with any of the prototypes.

The third prototype BI was fitted with retractable skis which could be interchanged with wheels depending on the ground conditions.

On a Gruzdiev flight, when lowering the gear before landing, one of the skis fell off, but the BI was nevertheless able to land without complications.

The sixth and seventh flights were executed by Bajchivandzhi on the third BI-3 prototype. In the seventh flight, on 27 March of 1943, the planned tasks included a top speed of 750 or 800 km / h at 2000 meters. As observed from the ground, the flight remained normal until the completion of the engine work in 78 second of. After finishing the engine operation, the plane lowered its nose and plunged at a 50-degree angle until it hit the ground. Pilot Gregory Yakovlev Bajchivandzhi died in the accident.

The commission studied the catastrophe but could not determine its causes. As a result, the report included that the causes were motivated by phenomena not studied at speeds between 800 and 1000 km / h. In the opinion of the commission, at these speeds, new factors appeared that influenced the direction, stability and load on the controls.

By 1943 a new T-106-TsAGI aerodynamic facility for high speeds was installed at the TsAGI. In it, tests of aircraft models and their elements began to be carried out to analyze their behavior at high speeds. Among them, the BI model was tested to find the causes of the catastrophe. From the results obtained, it was clear that the BI was destroyed because the peculiarities of the straight wing and tail at speeds close to those of sound that led the aircraft to dive, were not taken into account. It was estimated that at the time of the accident the aircraft piloted by Bajchivandzhi reached 900 – 990 km / h. In 1973 Gregory Yakovlev Bajchivandzhi was posthumously awarded the title of Hero of the Soviet Union.

As a result of the accident, the entire production of 30 pre-series BI-VS in different stages of development was destroyed. Despite this, the flight test program was continued with a number of modifications, it was hoped, would ease the difficulties.

In May 1943 OKB-293 returned from evacuation to Moscow, being relocated to the Khimki area, Moscow District. By the following year, another 5 of the BI had been built, called BI-5 to BI-9.

The endurance of the BI was in adequate for operational use, but a two-chamber engine developed by Dushkin to overcome this deficiency with low (cruising) and high (combat) thrust settings was almost double the weight and considered unsuitable.

In order to study the possibilities of increasing the endurance of the aircraft beyond two minutes of rocket motor work, in 1943 – 1944 modification was planned using ramjets or ramjets at the wingtips. In spring 1944 the sixth BI-6 was fitted with two DM-4 ramjets designed by I. Merkulov and tested in the TsAGI-101 wind tunnel, but was never flown. This ramjet was also tested on the Yak-7B fighter.

There was also an attempt at some point to seal the cabin by covering all the joints with resin bands, but this idea was scrapped.

After the loss of the Dushkin D-1-A-1100 engine, Isayev began to design his own engine, taking into consideration the advice received from Glushko and the experience accumulated during the tests of the BI. The new RD-1 engine was completed and tested in October 1944. In general, its dimensions were similar to those of the previous one, but it presented a large number of improvements and it was built with 12J13 steel with greater resistance to corrosion. The head had 85 injectors located in a honeycomb conformation that highly improved efficiency and featured an electric start system.

In January 1945, on Isayev’s BI-7 with ski landing gear and RD-1 powerplant, pilot BN Kudrin made two flights. In the first, on January 24, the plane was seriously damaged in an emergency landing due to a problem in the landing gear of the skid. On March 9, properly repaired and with some modifications, with a takeoff weight of 1800 kg and speed of 587 km / h, a climb speed of 87 m / s (4980 m / 16,340 fpm) was reached. The BI-7 revealed dangerous vibrations (flutter) in the tail section. To study the problem, on 29 March 1945, MK Baykalov conducted tests in the BI-7 in configuration as a glider. At that time, the BI had great damage caused by corrosion, so it was withdrawn.

The BI-5 and BI-6 specimens were modified to the same configuration as the BI-7 and flown as gliders towed by a North American B-25J. The BI-5 was tested with a ski undercarriage, being flown by BN Kudrin between March 10 and 25.

The BI-6 flew with conventional wheels, being piloted by MK Baykalov between April 25 and 29. During these tests no vibrations or other problems were observed, but by then it had already been decided to leave the program.

The Bereznyak – Isayev BI was flown with a reactive engine 9 times, 7 times with the Dushkin D-1-A-1100, and twice with the Isayev RD-1. It is argued that three more flights were made in the spring of 1944 with the DM-4 ramjets designed by I. Merkulov, but the truth of this claim has not been proven. These proposed flights were carried out by Kudrin to test ramjets, which were activated already in the air, after towing the BI-6 with another plane.

Flights with BI engine
Date	Model	Pilot	Power (kg)	Working time (s)	Height (m)	Speed ​​km / h	A. Ascent (m / s)
May 2, 1942	BI-1	Bakhchivandzhi	500	13	1	—	—
May 15, 1942	BI-1	Bakhchivandzhi	600	66	840	400	23
January 10, 1943	BI-2	Bakhchivandzhi	800	63	1100	400	—
January 12, 1943	BI-2	Gruzdiev	1100	58	2190	675	—
March 11, 1943	BI-2	Backchivandzhi	1100	80	4000	600	82
March 14, 1943	BI-2	Backchivandzhi	1100	84	3000	+/- 650	—
March 21, 1943	BI-2	Backchivandzhi	1100	30	3000	– 160	—
March 27, 1943	BI-3	Backchivandzhi	1100	89	2000	+800	—
January 24, 1945	BI-7	Kudrin	1100	72.3	1250	587	87
March 9, 1945	BI-7	Baykalov	1100	73	3500	550	—

Note: This table does include the first “take-off” of May 2, 1942, although this was never considered an IB flight.

Berez-Isa BI
Engine: one 1100-kg (2,425-1b) thrust Dushkin D-IA-1100 rocket
Wing span: 6.48 m (21 ft 3 in)
Wing area: 7. 00 sq.m (75.35 sq ft)
Length: 6.40 m (21 ft 0 in)
Height: 2.06 m
Empty weight: 958 kg (2,112 lb)
Maximum take-off weight: 1683 kg (3,7 10 lb)
Fuel and reagent weight: 600 kg
Max speed (estimated): 1000 km/h (621 mph) at 5000 m (16,405 ft)
Climb to 10000 m (32,810 ft): 59 seconds
ROC: 4920 m / min
Endurance: 2 minutes powered
Armament: two nose-mounted 20-mm ShVAK cannon
Accommodation: 1