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Thursday, 09 February 2012 11:50

The Sukhois Part 1/3

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SU-26 (S42)

There is no doubt that the Sukhoi Scientific Industrial Complex - with its headquarters in Moscow -  has earned an excellent reputation over the years in the world of military and aerobatic aircraft for the quality and originality of the majority of the aircraft they have built. Founder Pavel Sukhoi, being no friend of Stalin and seeing his business dissolve for a period of time, reappeared gloriously again in the year 1950 when the majority of his products were widely used by the Soviet Union and its allies. World-renowned designs, like the "Su-27 Interceptor" and the aerobatic Su-26 dominated the record books and were symbols of the international commercial potential that was cooking in the Communist era.

The Sukhoi, specifically models 26, 31 and 29, are widely known in the world of aerobatics for their reliability, robustness, maneuverability, and for receiving over many years the highest honors in international aerobatic competitions (and continuing to do so). And it has only been 28 years since the first purely aerobatic Sukhoi aircraft took off on its first flight - a flight that marked a “before” and an “after” in the world history of aerobatics.

It all started at the central offices of Sukhoi in Moscow during the year 1983, thanks to the initiative of its general designer M.P. Simonov who was driven by the need to create a new aircraft as a result of the plague of accidents that the Russian team suffered as a result of breaks in his Yak-50.

A group of enthusiasts from the design department, under the orders and guidelines of the creator of the Yakolev 55 and 55 M, Slava V.P. Kondratyev, began developing a new revolutionary aerobatic aircraft under the designation of S42, that would forever change the rules and perceptions of aerobatics worldwide. The development followed the performance requirements of the Central Committee of the USSR DOSAAF, an organization formed by the Army, Navy and Air Force that, among other things, was responsible for the development of the paramilitary sport in the Soviet Union.

P.O Sukhoi

The new model included the following features:

-High power : weight ratio that would be achieved through a robust design and the weight of the structure kept to a minimum.

-A wing configuration with a special symmetrical aerodynamic shape to allow a level of superior piloting.

-A robust structure capable of holding loads higher than + 12 / - 10 GS.

-Extensive use of "composite materials" in the design.

-An ergonomic cockpit configuration.

The design work involved pushing the limit maneuvering load to a new level in the aerobatic aircraft, which until then had never been exceeded or put to the test, as well as supporting a new and demanding level of piloting. It was just a matter of time before, thanks to the use of impartial testing systems, it was demonstrated that the pilot on board the plane could safely endure a wide regimen of aerobatic maneuvers and withstand accelerations exceeding 12 G. The new design of the aircraft took into account the views and experience of the pilots of the USSR national team, as well as the latest technology and trends in aerobatics. As a result, the design was the basis of new guidelines that were used in the development and construction of a high performance aerobatic aircraft.

In May 1984, B.V. Rakitin went in front of the Sukhoi Design Bureau to take responsibility for the project of constructing aerobatic aircraft.

On June 30, 1984, at M.M Gromov Airfield in the town of Zhukovsky, the first prototype, with the name of Su-26 (S42-1) took off for the first time with the former driver of the national team of the USSR Evgeny Frolov at the controls. Later, this pilot became a national hero.

M.P Simonov

In the two weeks that the test flight lasted, the USSR national team pilots were able to test prototypes. The Su-26 "performances" solidified the view that they were superior in flight, and that its extreme maneuverability and control were its strong points. The plane "rotated" at the speed of 1 revolution per second (over 6 rad/s). No other aircraft in the world had such features at that time. A high Gs level was generated with minimal lever movement. The pilot had a full view of his surroundings from the cockpit.

The aircraft was presented for the first time in competition in August 1984 during the World Championship held in Hungary. Pilot Yurgis Kairis came in 24th place in the Individual category. Despite the modest result, participating in international competitions gave them the experience necessary to re-design and modify the aircraft. Efforts were mainly focused on reducing weight.

To enhance its maneuverability and controllability, it was necessary to lighten and strengthen the plane enough so that it could withstand high Gs levels, extend its limits, and keep everything in good aerodynamic form. The problems were solved by introducing state of the art materials – robust and lightweight composite materials like plastics reinforced with carbon fiber, organoplastics and plastics reinforced with fiber glass as well as stainless steel, titanium and aluminum alloys. The Su-26 was used to test the new wing design and fins. In a short space of time, the design office produced the necessary documentation to improve the aircraft, which was designated Su-26M.

Su-26 M became the first aircraft of the USSR - the first aerobatic aircraft worldwide - to incorporate large-scale advanced composite materials which, all-combined, made up more than half of the airframe. Sukhoi implemented for the first time the principle of "indestructible in the air" aircraft, which meant that no matter what the pilot did in flight, it would be impossible to generate a load high enough to produce a break for the first time. In the static analysis, the wing approached the breaking point when the plane reached the incredible load of 22. 5Gs. The aerodynamic characteristics of the aircraft made it impossible reach more than 18 Gs in flight. The 12Gs operational limit is imposed due to human physiological capacity.

To ensure that the pilot was able to withstand these extreme Gs forces, the cabin was designed ergonomically, including an anthropometric seat with a 35 degree inclined backrest and a unique safety harness. This made it possible for the pilot to control the position of the aircraft at all times.

The weight reduction that applied to the aircraft was of such magnitude that the SU-26M managed to break the world record for power:weight ratio for all aerobatic aircraft worldwide.

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