Our correspondent met with the President of the hang gliding Federation of sports of the USSR Evgeny N. Yelizarov and asked to tell about the development of this technical sport in the country.
— The time has come when the sky can be described as a mass form of aviation sport. The basis of this — the creation of a production model of the glider, which is an educational-training apparatus “Slavutich-UT”, successfully passed the tests, as well as continuing development of new types gibcobrl gliders.
The new is born in the difficulty in overcoming divergent views. This fate is not passed and the glider; the period of its formation can not be called easy.
Despite the apparent extreme simplicity of the device apparatus frame of light pipes and cables-braces, soft fabric covering, the glider has a high severity in the aerodynamics and piloting. That’s why there were so many disputes around the question: to design or not to design enthusiasts their design megacrush gliders. All those who responsible for safety in hang gliding, waiting for the creation of the unit, serial production of which would be removed from the agenda this question.
— And now developed and tested “Slavutich-UT”. Does this mean that the construction of the gliders on their own has to stop?
— Now on this question the Federation is clear: you can build. But in that case, if there are appropriate technical documents, drawings approved by the technical Commission of the Federation and the necessary materials. And again: in any case, it is not a valid Amateur work, being too Amateur, low qualification — theoretical and practical. All this we say a firm “no!”. Without knowledge of the theoretical foundations of hang gliding who really wants to master the design and flight, to improve, and not become a victim of thirst for thrills in the first take-off, has no right to start.
— Where and how to organize such activities of deltaplanerism?
— Only in the flying club section, only under the guidance of experienced designers and specialists of gliding you can do this. And That has already been built, must be subjected to the most exacting of tests, the overflights to be in the hands of a skilled, technically competent glider pilots.
— I would like once again to underline to what extent and whether it is possible to design NEW gliders?
— Not only possible, but necessary. Hang gliding is not only a young sport, but promising industry technical creativity. Here a wide field to search for the most rational solutions to construction, disclosure and the use of aerodynamic and flight “reserves” of the glider, its stability, controllability, flight qualities. We can say that our gliders-designers we have compiled extensive and interesting experience happened even if you want your direction in deltaplanerism — for example, Leningrad, Kiev, Moscow.
— What should be included in the basis of design of each new glider?
— First of all reliability, good stability and high maneuvering properties, safe operation. In the name of security design introduced only checked by experiment technical solutions: ANY flight should be completed safe landing.
And deltaplanerism used for this purpose, in their machines a lot. One of such findings is developed the size of the terminal parts of the wing that received because of its shape called “mugs”. A long search of optimal cutting tissue going to the sewing of sails, allowed to solve this problem. After the tension on the frame of the sail, sewn in such a way, the wing tips were clearly defined space with a negative twist. In flight at high angles of attack “mugs” modify existing forces so that the device becomes more stable. Tests showed that the negative twist the end parts of the wing has a positive effect on the ability of the apparatus to resist dive.
New technical ideas and their implementation, plus the obligatory pre-testing — this should be the style of creativity of building gliders not to mention, in this regard, about such promising areas as finding the most advantageous contours of the wing of the glider.
It took some engineering daring to apply classic fundamentals of aerodynamics and design of aircraft heavier than air gliders.
Who is familiar with the basics of aerodynamics, he knows that the elliptical form in plan, the wing has less inductive reactance than all the others equal him in size, but different shape wings. This theory was waiting for their confirmation and for the flexible wing.
What it means to give the wing keel beam in the form of the Latin S? This means to give the wing profile in the zone of the beam S-shaped loop. In the language of aerodynamics it sounds as improvement of the torque characteristics of the wing. Do: S-shaped profile as if guarding the wing from the desire to go on a dive. For rational cutting of cloth on a sail there are already theoretical designs and even working snap-in in the form of templates and Platov.
Many gliders of perfecting a system of horizontal suspension type “apron” for the pilot; attention is being paid to the search for better equipment, until the development of uniform subject to the requirements of technical aesthetics.
— But new glider built. What is the further way of its use?
— Each built unit should be thoroughly tested and fly around first, just with cargo, then with the help of an experienced tester. The pilot establishes himself on camera and as a beginner, begin with short runs. If the glider docile and controlled, and skilled athlete feels good, choose a small slope and make him approach without moving far from the earth. If the machine with multiple approach remains stable, climb higher and explore his “nature” in free flight.
— That the design of the device is often the Keeper of the secret of disobedience, which can suddenly occur in flight?
— First of all the very wing or sail. Deltaplanerism have to remember that contrast to the rigid wing flexible is able to change its shape. It depends on the distribution on it aerodynamic loads, a Significant role is played here not only the rigidity of the frame, but the “malleability” of the fabric under load: the final form of the wing is formed by the pressure of the air flow on the sail. The smaller coolest and wing area, the greater the strain on the fabric of the dome.
At the same time change the shape of the flexible wing may occur the deterioration of stability and controllability of the glider. You need to keep in mind that the properties of materials such as, for example, Bologna, highly dependent on humidity, so they should not be used in the apparatus with small kupelnou.
At small angles of attack of the flexible wing can lose shape. This phenomenon is accompanied by a “rinse” is an intense wave-like movements of the plane of the sail. Unwanted effects can cause the loss of the wing a negative geometric twist up to tighten the machine into a dive.
So the glider should bear PA also additional devices that would cause his desire to exit from the dive. This will guarantee the stability of the apparatus at various angles of attack.
— What means gliders seek to ensure longitudinal stability of the apparatus and which of them can be recommended as promising?
— Some of them I’ve already mentioned. The main recommendations for improving the longitudinal stability of the glider can be attributed to: a decrease in the angle at the vertex of the frame, negative twist, the introduction of the V shape of the keel pocket. Overall, however, this problem is still waiting for new design solutions. Because the hang glider compared to other designs for gliding flight — aircraft extremely sensitively and subtly perceive the action of the surrounding air.
— What would you wish everyone working on the improvement of the glider?
— First of all not to get carried away by the excesses of modernization of the machine. Now, for example, many are trying to build the trikes. This is an interesting and promising direction. But we must not forget that the glider in the first place balance planning unit and the inclusion in its motor design is a violation of the formula of the glider. Let’s take a related example — a sports sailing yacht. It is like a sailing ship is good because it allows you to fully use all the features and benefits of the Union of the sails and the wind to reveal the art and skill of steering. After all, nobody will come to such a class of vessels to mount the engine. And rightly so.
You need to look for technical solutions that would allow fuller to use the aerodynamics of the flexible wing.flying qualities of the glider in accordance with its specific principle of control and piloting.
By the way, now flightless designers of gliders, are passionate about solving such technical problems, no less than flying. And this is seen as another important aspect of hang gliding is a form of art that stimulate the forward movement of design and inventive thoughts of a great army of young enthusiasts of technical creativity.