LOMONOSOV WAS THE FIRST"Krasnaya Zvezda", 12.07.2006
The Farnborough -2006 air show to be opened on July 17 promises to be rich in sensations. According to western mass media, the “Sikorsky” company plans to demonstrate advanced rotorcraft with coaxial rotor scheme, capable of flying at cruise speed of up to 450 km/h. It is asserted that American designers managed to improve aerodynamics of a helicopter by significant reduction in the drag of the coaxial rotors to the level of a single-rotor helicopter. We asked the most competent authority in this field – General Designer of the “Kamov” design bureau, hero of Russia, Sergei Mikheev to comment on this information.
- Sergei Viktorovich, the “Sikorsky” traditionally developed single-rotor helicopters. In your opinion, why did it begin to work on coaxial rotor schemes, thus changing its priorities in the helicopter industry?
- First of all it is necessary to return to some historical events. The coaxial rotor scheme is older than a widespread single-rotor design by 157 years and this fact is documented. Mikhail Lomonosov was the first to develop a coaxial rotor scheme, the certificate of authorship for the second one belongs to Boris Nikolayevich Yuriev (1911), later an academician of the Russian Academy of Sciences.
I would like to mention another very interesting historical event. From 1908 to 1911 Igor Sikorsky, a student of the Kiev Polytechnic Institute was making two attempts to build full-scale coaxial helicopter prototypes. At first glance, its design solution was optimal.
I will make an explanation without going into details of aerodynamics. During rotation of a rotor the lift is created causing torque reaction in the direction contrary to the blades rotation. Therefore, the first solution for compensating torque reaction was to install on an axle one more similar rotor rotating in counter direction. But this idea appeared difficult to carry out technically. Sikorsky failed to take off the new helicopters as the engine power of 25hp was insufficient.
Then Igor Ivanovich Sikorsky, the bright design engineer gained a world-wide recognition in several spheres of aviation, including helicopter building. In the end of his life he returned to his “first love”, he made an attempt to create a coaxial helicopter and to reach a level inaccessible thus far in the world aircraft industry. The fact is that the helicopter must operate equally well in hovering and in level flight, when it has to fly as fast as possible. When a single rotor helicopter flies at flight speeds higher than 350-400 km/h, some problems appear which cannot be solved even theoretically. In level flight a rotating rotor experiences a rolling moment, because one side of the disk has substantially larger lift force as compared with its other side’s. And the higher flight speed, the greater this difference.
This is why until recently it has been practically impossible to trim the helicopter at flight speed of more than 400 km/h.
How can we solve the problem? As it proved to be, in the same way that Lomonosov did: by installing the second contra-rotating rotor. It is certainly not a simple task to realize technically, but the coaxial prototype, built in the late 70s managed to develop a flight speed of 408 km/h thus demonstrating and proving the viability of such solution. As you see, it was quite natural that the “Sikorsky” company returned to the X-2 model and made the following step towards the development of helicopters, while the technological achievements of last years allowed to have made this step.
- So the Americans would not scruple to duplicate our solutions, would they?
- Not exactly. It goes without saying that the USA keeps a close watch on our work. Many American test pilots had a possibility to estimate special piloting features of the Ka -32 helicopter in Canada and to compare its characteristics with single-rotor analogues. In late 90s a large delegation from “Sikorsky” company headed by their President arrived in Moscow, they also visited our company. We showed them demo flights of the Ka-50 helicopter, and, in particular a maneuver, during which helicopter makes a 90° turn at a speed of 250 km/h and continues flight sideward. This greatly astonished our guests, because “theorists”, to be more exact opponents of the “Kamov” company, assured everybody that such maneuver is impossible. By the way, the similar maneuver was then only elaborated for the advanced “Comanche” helicopter.
As for duplicating, paradoxical as it might seem, it can be easy and difficult at the same time. Ideas are in the air, but in order to understand, that their time has come and to find simple and effective solutions for their realization, one should have a talent. The idea itself is only a slogan, it is necessary to know how to put them into life. It is easy to copy, but you will obtain only a moderate duplicate at best. It is necessary to work independently at all stages of a project from “A” to “Z”. For production of any equipment one needs appropriate industrial and engineering capabilities, and most of all - design solutions. At this very stage the problems appear to be like an insurmountable wall. So the only way out is to study experience and versions of technical solutions used by competitors, and then on the basis of them to find their own solution. For example, recently the “Kamov” company has issued a monograph of 800 pages on theory and experience of creation of coaxial helicopters. In the USA they have already began to translate it and to prepare it for publication. Our considerable achievement is the creation of Ka-50 helicopter which could attain a speed of 400 km/h during tests. It goes without saying, these are the main milestones and priceless experience, but the American X-2 project is intended to be a breakthrough into the future. The USA designers will use only their own experience and they won’t share it with anybody else, as the information is highly valuable.
- Please, comment on reports of some foreign press concerning the fact that the Americans give special attention to surface aerodynamics. Is it true that the Americans managed to decrease the parasite drag of coaxial rotor to parameters not above those of a single-rotor helicopter? What do you think about it?
- The Americans are seriously approaching the subject; it can be proved by the following fact. In May current year there was held an annual forum of the American Helicopter Society. 3 reports of 18 reports on aerodynamics were dedicated to coaxial rotor studies, moreover, to such important aspects, as optimization of blades parameters and dynamics while maneuvering. These things did not just happen, did they?
In fact, they traditionally believe that the coaxial-rotor design inherits high parasite drag that is why the maximum speed of coaxial helicopters is less, than that of single-rotor helicopters. The Ka-50 has retractable landing gears, as a result the maximum speed of “Black Shark” and its single-rotor analogs is identical. It is necessary to explain, however, that for many years Kamov’s designers have made successive steps to simplify the rotor system design and to reduce its parasite drag. However, the high-speed coaxial rotor advances a number of requirements and once these requirements are met, it will be possible to drastically improve this feature, no matter how paradoxically it sounds.
At present a huge volume of researches and developments are conducted to create a new generation rotor system abroad, ensuring high flight speed and high lifting capacity. To support design and estimate new coaxial configurations the corresponding means of analysis and calculation are being developed.
Not to be accused of the prejudice, I will refer to the opinion of some English researchers noting the revival of interest in coaxial helicopters “as a technological solutions meeting operating requirements on high speed, improved maneuverability and high lifting capacity of rotorcraft. Historically Russia was the most important developer and operator of coaxial helicopters… In some most innovative designs, such as the Sikorsky’s Advancing Blade Concept (ABC), and also in Kamov’s Ka-50 combat helicopter there was made an attempt to use a coaxial design for obtaining improved flight performances". In this regard I can only refer to a Russian saying: “no man is prophet in his own country”.
It is also absolutely clear why they pay much attention to fuselage aerodynamics of the test X-2 helicopter. Just the advanced aerodynamic shaping of fuselage and the very high lift-to-drag ratio of high-speed rotor will allow improving aerodynamic quality of a whole rotorcraft. That is why the aerodynamic shape of fuselage is so crucially important - it is one of the components of success. Cruising speed of 450 km/h equals, indeed, to the speed of a light aircraft, and therefore, this problem shall be solved from the viewpoint of “aircraft pilots”.
- Foreign specialists show high interest in coaxial helicopters after Turkish tender. Which of the features of Kamov helicopters did Turkish specialists appreciate most of all?
- Indeed, not only Turkish party expressed high interest in the Kamov’s helicopters during the ATAK program tender. Moreover, our participation made it possible to estimate all basic types of combat helicopters being developed across the world not by mere comparison of advertising booklets and statements of developers, but in the process of flights according to flight test program. I jokingly called this tender the world championship of combat helicopters. Our two helicopters (Ka-50, Ka-52) participated in the tender. A short, but informative conclusion was made for each helicopter: “while in the air the helicopter demonstrate an amazing level of stability”. For pilots this expression is highly informative and it is better of any praise for a helicopter. In Turkey the Ka-52 helicopter carry out 30 qualification tests using all types of armaments. All flights were carried out perfectly without any failures and malfunctions.
Turkish pilots inspecting Russian helicopters checked not only the capabilities of weapons. They studied very attentively the stability of helicopters during gun shooting and use of unguided aircraft missiles, focusing special attention on missile dispersion area and determining the lethal range.
The examiners were pleased that all declared data were confirmed during fulfillment of flight missions, and after the fulfillment of standard combat mission the helicopter fuel tanks had still some fuel remained. For us, however, it was natural, as on the eve of the tender we completed state tests, having fully met the demands of Russian customer. I want to emphasize that the Ka-50 state tests program for compliance with the assigned requirements was conducted without any condescension and it was carried out completely. This allowed the Russian army to include the Ka-50 helicopter in the inventory already in 1995.
One of the special requirements for a combat helicopter is a hovering ceiling of 4,000 m above sea level with assigned payload and 2 hr fuel reserve. This feature became practically standard for all countries. We have met the standard for last 20 years, in spite of changing requirements. The coaxial design is the core feature making possible for us to lead in comparison with other helicopters developed at the same time. In order to gain our advantage on hovering ceiling, our competitors would have to redesign their helicopters. It is possible in terms of theory, but it is impossible in terms of practice.
International competitions are a rigid thing and even severe one, as there are no spineless judges there. Of course you can hope for policy decisions, but in any way technical specifications must be irreproachable.
- Let us return to the subject concerning the nearest future of helicopter industry. Please explain, does Russia have developments similar to American ones, and at what stage of realization are they?
- I would not open a state secret, if I tell that, at least, our design bureau, have similar developments. However, the R&D works of the Russian helicopter industry are poorly financed now, and our ideas seem to be put away in cold storage. The Russian history has already known such cases, when having obvious priority, we first lose the monopoly, then the leadership and finally we have to import western technologies…
- How do people, in your opinion, benefit from creation of a high-speed coaxial helicopter?
- I think that it will be a real technical revolution. Just imagine an attack helicopter being as maneuverable as the “Black Shark” and having speed two times higher. Another model of transport vehicle developed by our design bureau is also very interesting. It will be a “combined helicopter” intended for transportation of 30 passengers or 2,500 kg of urgent cargo with cruising speed, at least, 400 km/h over a distance of 1,400 to 1,500 km.
Such helicopter would make it possible to create a regional transport system of the Extreme North and the Far East without enormous expenditures for building an airport infrastructure. It must change the air carrier’s idea about helicopters, as the main transport vehicle in the north will have the same speed as a regional aircraft. The helicopter can serve as base for establishing a cost-effective passenger air service in the polar region and a reliable communication with the continent. For example, our “combined helicopter” could become the main transport means on the Murmansk-Shtokmanovskoe deposit route.
For the EMERCOM such rotorcraft could constitute the backbone of highly mobile all-weather air rescue service. For the Federal Security Service of Russia the “combined helicopter” would serve as an effective means for guarding frontiers and economic zones. Finally, the new vehicle would be able to provide special units with the required mobility.
The “Sikorsky” company is going to fly X-2 this year and being sure of the success it is already designing a rotorcraft equipped with rigid coaxial rotor system. It appears not to be just a concept but a real and economically feasible helicopter. I believe that if we operated this helicopter, we would give a new impetus to further exploration of Siberia and the Artic Ocean.
Finally, it remains to answer some seemingly simple questions. At present the economic position of the country is becoming steady, priorities are noticeably shifting. If earlier the state budget items were poorly paid, then now the Chairman of RF Government, Mikhail Fradkov reproaches ministers that they “do not manage to spend the allocated budget”. The President of Russia, Vladimir Putin set a task to develop breakthrough technologies to secure the country’s leading positions in the world.
In spite of hardships of the past two decades, the creative and design potential of the country was preserved.
May be, it is high time to follow the example of the Americans who once joined the lunar race and upgraded not only missilery, but also adjacent branches, and to set a worthy and ambitious goal - to develop a brand new type of transport and to regain world leadership in the helicopter building industry?
Indeed, the problem of developing of a brand new technology is worth being the subject of a federal or presidential program.
Interviewed by Yuri Avdeev
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