The Incredible Secrets of the Inverted Wing Design

It's an experimental supersonic jet fighter, a technology demonstrator, developed by Sukhoi Corporation. The S-37 project, as it was called at that time, was projected as the first air superiority fighter for the Russian Air Force. The most characteristic feature of the Sukhoi Su-47 is its inverted arrow-shaped wings, and it had its first flight in 1997. The Berkut, which means Golden Eagle or Royal Eagle in Russian, initially used only an S instead of its current SU designation because it was an experimental design ship and not a series. It had been designated as S-32 and S-37 during initial development, and although the Berkut has also been referred to as Su-47 since 2002, suggesting a device ready for production, the reality is that it has been used as a prototype to demonstrate new technology that the most current fighter planes of its joy have used. Welcome to a new video from the Aeropedia of Aviation World. In the 80s, the Central Institute of Aerodynamics was very aware of the advantages of the forward swept wing, or inverted arrow wing. Their research included the study of the Junkers captured in the 1940s in Germany during the Second World War. The S-37, as it was called at that time, was projected as the first air superiority fighter for the Russian Air Force, successfully utilizing the principle of forward swept wing technology, or inverted arrow. This had been the mock-up or initial model of the project, and notice how different it was from the first prototype. Swept wings produce greater maximum lift, reduced bending moments, and late stall entries, compared to more traditional wing shapes. At higher angles of attack, the wingtips remain without stall. That is the phenomenon of entering into loss, loss of lift, and this allows this type of aircraft to maintain control of the ailerons at lower speeds. The airflow over the positive or regressive swept wing tends to slide to the outside of the marginal edges. With high angles of attack, the airflow will move away from the wing, rendering the external control surfaces ineffective. On the other hand, with a negative or progressive swept wing, the air tends to move inward. Even if the airflow separates from the wing, the external control surfaces remain effective for longer, and control can be maintained even at quite high angles of attack. In the positive or regressive sweep, with high angles of attack, the airflow moves away from the wing, which tends to stall at the wingtips. In the plane with positive sweep, the ailerons become ineffective and control of roll and maneuverability is lost. In the case of the negative or progressive sweep, although in this case the air also moves away from the wing, the tendency of the airflow is towards the inside, which makes the ailerons remain effective for longer, and the plane can be controlled even at the limit of the stall. Unfortunately, and already the flight tests with the Yunkers 287 also revealed the basic problem of this concept, and why today we do not see so many planes with this. The negative sweep accentuated the tendency for wing twist, which under heavy loads tended to separate from the fuselage. The solution came with the materials. Based on thin carbon fibers bathed in a resin that hardens when subjected to heat, resulting in a high-strength product. The speed of the first prototype of the S-37 was only Mach 1.6 compared to, for example, the 2,500 km per hour maximum speed of the Su-27, and this is due to the air resistance of the new Canard's wing configuration, installed in front of the main wings and advanced almost to the cockpit. And its new unconventional design of inverted delta wings was the real innovation of the plane. The flight control system was computerized and fly-by-wire type, or something like electronic control piloting in Spanish, similar to the one used in the previous project that was already in the testing phase in the Su-35. It allowed the aircraft's aerodynamics, which are very unstable in nature, to be controlled at all times by the new flight computers of the plane to prevent it from stalling, assist the pilot in take-offs and landings, and to allow him to focus on combat missions. The Su-47 could perform maneuvers of up to 9G and was going to have no less than 14 anchor points like its Sukhoi brothers. It had a new sighting system for combat against other fighter planes, an infrared search and track similar to the one that had been tested in the experimental fighter, the Su-35, of the Su-27 family of mass-produced planes, with a targeting system integrated into the pilot's helmet in a small dome with a transparent cupola over the radar cone on the right side of the cockpit windshield. It's a system for searching and tracking enemy targets by infrared. It operates on two radiation frequencies and is used, along with the ship's radar, in air-to-air combat missions against other fighter planes in close combat or dogfight. The Berkut's wing is made up of 90% composite materials. The fuselage is made of aluminum with a titanium alloy and 13% composite materials, with a low-detection coating for radars. Although it has not served in combat and was used as a test model, its work in the development and improvement of Russian aviation has been quite remarkable. It is considered as the base experimentation platform for the development of the new fifth-generation air supremacy fighter, the Su-57. It was a large twin-engine, single-seater plane with measurements similar to its cousins derived from the Su-27, with a maximum take-off weight of 35,000 kg and it was expected to have a range of 1,800 km. The project had started in 1983 on behalf of the Soviet Air Force but when the Soviet Union dissolved, the funding ended and the development continued only thanks to Sukhoi's own financing. Like its American counterpart, the Grumman X-29, the Berkut was primarily a technology demonstrator for future Russian fighters such as the Su-35 and the one we already mentioned, the Su-57. The forward-swept wing configuration was not chosen because it was primarily advantageous at transonic speeds while a backward-swept wing is superior at supersonic speeds. And that's why to this day you see more of these conventional types of wings. Until a new video, I hope you liked it. I'm Marcos and this is the Aeropedia of Aviation World.