All Aero

It was that VM Molotov’s international espionage system had received information about the development in the United States of a low aspect ratio aircraft designed by the Russian émigré Glukhariev. When asking the TsAGI about the subject, the scientists from this institution could not give an objective answer, since they generally worked on more conventional designs. About six months later the information reached Stalin, who paid great attention to aviation and decided that behind that news there must be an important aeronautical development. Suddenly someone remembered about Moscaliev’s shelved project “Sigma”. It was decided without fail to call him to Moscow.

After exposing the characteristics of the “Sigma” project and defending the theory of the development of aircraft with this scheme and reactive engines as a way to achieve high speeds, Moscaliev received the task of building an aircraft analogous to the “Sigma” in the OKB-31 and submit them for state testing. The TsAGI was ordered to carry out experimental work in the wind tunnel on a scale model and the additional task of beginning studies and developing a low aspect ratio model. Its construction was assigned to the specialist of the TsAGI Kamniemostski.

For Moscaliov’s new plane, two 140 hp Renault 4 pi engines were purchased and the decision was made to name the model Moscaliev SAM-9 “Strelá” (Arrow) (Russian: Москалёв САМ-9 «Стрела»), due to the shape of its fuselage in the plane. Moscaliev was given two and a half months to get the prototype ready. The short time was motivated by Stalin ‘s interest and the need of the TsAGI to give a quick response.

The conceptual project of the new aircraft was developed by Moscaliev still in Moscow . For this purpose, Professor Cheremujin ‘s office at the TsAGI was lent to him and he was assigned cartoonists and copyists. This project was ready in just three days.

The general composition of the new aircraft was approved by TsAGI Victor Pavlovich Gorski. In general, the “Strelá” kept the wing shape of the “Sigma” but lacked the horizontal surfaces at the wing tips, presenting a conventional empennage with rudder.

It was agreed to work in parallel in two directions: the creation of a mock-up for the development of the tests at TsAGI, under Gorski’s tutelage, and the construction of the aircraft at the Voronezh Aviation Technology under the direction of Moscaliev. The construction of the aircraft without having received the checks from the TsAGI represented a great risk, but the short time allotted to the task did not allow another sortie. Moscaliov ‘s OKB was isolated to dedicate itself exclusively to this new task, which had a strategic character and for that reason it worked with a high level of secrecy. In the agreed two and a half months the new aircraft was found finished. In the numbering of the company it became known as SAM-9.

The SAM-9 “Strelá” was entirely in wood with plywood and fabric covering.

The triangular shaped wing with elliptical sides and rounded base had a very low aspect ratio with an aspect ratio of 0.975. It was also characterized by the use of a very thick profile (RAF-38 modified) that started right from the nose. The wing structure consisted of three spars and box-type ribs with plywood covering. The control surfaces was carried out by means of cables.

The wing trailing edge was made up of two large-area control surfaces, which served as elevators. By reaching unequal angles these surfaces could also be used as spoilers.

The fuselage was integrated into the wing with a smooth transition and ended in a large-area empennage.

The landing gear was of the conventional type with a tail skid. The main undercarriage was cantilever type and fairings, featured unique balloon wheels.

The pilot was located in a closed cabin located on the wing with transparent cover. The power plant consisted of a 140 hp MV-4 engine (licensed version of the French Renault 4 pi) moving a 2.2 meter diameter Ratier wooden propeller.

The prototype was ready for the beginning of the summer of 1937. By that time, the necessary calculations and static resistance tests had been carried out. In parallel, tests were carried out in the TsAGI wind tunnel under the direction of VP Gorski. The results obtained allowed fine-tuning the details of the aerodynamic calculation, stability, definition of the center of gravity and the ideal size for the control surfaces.

It was decided to carry out the tests of the prototype in a remote airfield, used as a reserve base for long-range bomber aviation and located about 10 kilometers from Voronezh. As a test pilot, AN Gusarov was selected, who since the end of 1936 had left his position as head of the flight group of the Voronezh flying club and joined OKB-31.

Ground tests began on July 27. The new aircraft responded acceptably to the controls, behaving well in turns on the runway, increasing speed quite well and maintaining course without difficulty with the tail off the ground. The pilot was astonished to see that at a speed of only 70 – 80 km/h the plane voluntarily detached itself from the ground.

The factory test evaluation commission included the pilot, Moscaliov himself and a group of specialists made up of LB Polukarov, SA Zavyalov, NA Marietski and Dolgov. In August this commission was reinforced with the arrival of a government commission from Moscow. After once again reviewing the documentation, it was decided to proceed with the development of the tests. Due to the lack of a standard to define the structural resistance of this new concept, Professor VN Belyayev was asked to review the calculations and the results of the static tests, in order to give the go-ahead for the start of the flights.

After Belyayev’s positive assessment, it was decided that the flight tests would be entrusted to experienced test pilot Boris Nikolayevich Kudrin, who had previously tested unconventional configuration aircraft produced by Cheranovski and other Soviet builders.

Arriving at the site, Kudrin watched the plane for a long time, checking its parts. He reviewed the calculations and finally told the commission that he would not only not fly the plane, he would not even conduct ground tests on such a strange device. According to Moscaliev ‘s own words in his memoirs, the pilot Kudrin stated that he would not fly in an airplane “… that not only did not have a tail, but also lacked wings”

After several discussions, it was decided to continue the tests with factory pilot AN Gusarov, who gladly agreed to fly the prototype. Soon tail-up racing around the track began again. These were successful if one discounts an incident in which, during a race on the runway, the pilot stepped on the pedals and the plane suddenly went into a spin and overturned. Luckily neither the aircraft nor its pilot received damage due to the low speed and the grass on the runway. The plane was returned to its position on the wheels and the pilot, after starting the engine, headed towards the starting point. As a result of this incident, steel tube protection was added to the cabin deck.

Finally, the first flight was authorized, which was carried out by Gusarov on August 7, 1937. Around 10:30 a.m., after raising the tail of the plane, reaching about 150 km/h, it took off about 20 meters from where the commission was, making a dangerous turn that almost placed the planes in a vertical position to the ground, to then straighten out. After a flight of about 1,200 – 1,500 meters, the plane touched down.

Despite the pilot’s opinion that he maintained control over the plane at all times, the commission considered that the flight could have ended in a catastrophe and only the pilot’s expertise saved the plane. As a result it was decided to continue the tests in Moscow.

The aircraft was transferred on the bed of a truck to the TsAGI NII, located at the Central Aerodrome in Moscow. The tests this time were started from scratch. The races around the track were carried out by practically all the LIS pilots – Korzinshikov, Chernavski, Rybko, Ribushkin and even the LIS boss NF Kozlov, but no one showed up wanting to fly it. During these evaluations, well-known USSR test pilots such as Gromov, Alexeyev, Stefanovski and Chkalov were present, who expressed doubts about the flight possibilities of the plane, which increased the misgivings of the pilots to raise it. Finally, Gusarov decided to try again.

The flight was carried out with extreme care. The plane rose about one meter from the ground and after testing the operation of the ailerons it landed. Realizing that the model could fly and was capable of responding to commands, the SAM-9 executed several short, low-altitude jumps flown by Chernavski, Rybko , Ribushkin and others.

Nikolai Stepanovich Rybko was selected as test pilot who started the systematic flight program. Starting with short duration flights, he gradually increased the range until he achieved more than 1 kilometer. On August 27, Rybko reported that he was ready to carry out a real test flight that was carried out the following day and in which the plane failed to increase the altitude, so the pilot was forced to land at the neighboring Aeroclub Central aerodrome, in Tushino. The reason for the lack of height was the requirement of the new scheme for angles of attack greater than 22º to achieve ascent, motivated by the low engine power.

In the month of September a new flight was carried out, which was completely successful. The next flights of the SAM-9 were carried out already in winter on Lake Plesheyevo on skis and later again in Moscow. The tests lasted until the middle of 1938 and in them the performance of the airplane was fixed, despite the fact that it was understood that with a Wheel undercarriage the results should be superior.

In August 1938 the “Strelá” was returned to the OKB with a detailed report of the conclusions about his scheme and the request to solve a small problem of oscillations that appeared to fly at low speeds. Due to the secrecy of the project, the plane was packed in a big box and moved by train to Factory No.18.

After small modifications that included increasing the empennage area by 30% and installing vertical surfaces at the tips of the wings, further tests were carried out by AN Gusarov, which yielded a top speed of 343 km/h.

At the end of these flights and following orders from Moscow, the SAM-9 “Strelá” plane, which had already fulfilled its mission, was destroyed.

SAM-9 “Strela”
Power plant: 140 hp MV-4
Prop: 2.20 m diameter Ratier
Wingspan: 3.55 m
Wing area: 13.00 m²
Length: 6.15m
Empty weight: 470 kg
Maximum takeoff weight: 630 kg
Wing loading: 48.5kg/m²
Power load: 4.5kg/hp
Fuel + oil load: 60 + 10kg
Maximum speed: 310 km/h
Landing speed: 102km/h
Service ceiling: +1500 m
Landing run: 100m
Take-off run: 200m
Accommodation: 1