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Rotor with Dynamically Changing Parameters


The Rotor With a Possibility of Change of the Geometry Parameters In Dynamics

Tech Area / Field

  • MAN-OTH/Other/Manufacturing Technology
  • INS-OTH/Other/Instrumentation
  • PHY-OTH/Other/Physics
  • SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation

3 Approved without Funding

Registration date

Leading Institute
Georgian Technical University, Georgia, Tbilisi


  • The Boeing Company, USA, PA, Philadelphia\nPolitecnico di Milano / Dipartimento di Ingegneria Aerospaziale, Italy, Milan\nDeutsches Zentrum für Luft- und Raumfahrt e.V. / Progammdirektion Luftfahrt, Germany, Braunschweig

Project summary

It is known that propeller driven airplanes are more economic and ecological than jet. That’s why the creation of such a rotor that will be optimal during the whole period of flight is very urgent.

The fixed pitch rotors (FPR) and variable pitch rotors (VPR) are not optimal at the all stages of flight. The solution to this problem is possible only by the application of the variable geometry rotor (VGR) due to the possibility of simultaneous change of the diameter of the rotor and also of the setting angle and twist of blades in dynamics.

The VGR gives the possibility of especially effective optimization of flight of the airplanes with vertical takeoff and landing (VTOL) by provision of maximum diameter and minimum twist in hover mode and the contrary minimum diameter and maximum twist during the cruise flight.

The Project objective is the updating of the mechanism of the VGR blade diameter change combined with the system of compensation of centrifugal forces and extension of the twist range of blades. With this aim several versions of mechanisms have been developed from which together with the Collaborators will be selected the optimal one for fabrication and tests. The accuracy of scientific conclusions by means of the acting model will be demonstrated and also the prerequisites of certification of the VGR and Brand Management with the strategic aim will be considered. For the estimation of possibilities and limitation for promotion of the VGR to the market will be carried out by preliminary SWOT analysis.

Despite the multitude of works of famous companies and scientists of various countries the VGR problem has not been solved yet. There are patents, which did not find the real realization mainly because of a complication and insufficient reliability of technical solutions.

The Project participants are competent in the mentioned field. They worked in the International Science and Technology Center (ISTC) Projects G-060-2 “Variable Geometry Rotor (VGR) and Its Control Means (Actuators)” and G-916 “Controlled Rotor with Compensation of Action of Centrifugal Forces”. At the completion stage is Project G-1600 “Updating of the Mechanism of the Diameter Change of the Variable Geometry Rotor (VGR) Combined with the Compensation System of Centrifugal Forces and Extension of the Range of Change of the Blades Twist”.

During the implementation of G-060-2 Project the original variable geometry rotor (VGR) was created with combinations of the diameter and twist change during flight. The approach priority has been protected by the patents of the Russian Federation and Georgia.

The control mechanism units for the rotor diameter and blades twist change have been developed. The versatile program of the VGR model tests on the especially designed stand has been carried out. The tensometric and dynamometric measurements of the rotor thrust at various loads have been conducted.

The priority direction of the applied investigations of G-916 Project was the experimental proof of possibility of at least partial discharge of the mechanism of the rotor diameter change from action of centrifugal forces. In the compensation system of centrifugal forces was used accumulation of energy of the centrifugal forces action in hydro-pneuomo-accumulator during the extension of blades with its subsequent use for partial discharge of the mechanism of the rotor diameter change during the retraction of blades. Several designing versions of the system have been developed from which taking into account the opinions of the Collaborators the optimal one was selected and manufactured.

The synchronism of the VGR functioning has been proved.

This design because of the ISTC support received European Patent #08737551.5-2422 PCT/IB2008001041 of April 28, 2008. At present the necessary documentation for acquisition of Patent in the USA is registered and submitted.

The peculiarity of the VGR design used in Project G-1600 is that in the control system of the VGR instead of the jack-screw was used the control by cable, by that many big sized parts in the blade are absent that is very important for aviation. In this design the diameter increase, i.e. the extension of blades is carried out at the expense of arisen centrifugal forces. The retraction is achieved by means of the hydro-cylinder and special cable the loose ends of which are fixed on the movable parts of blades.

With the aim of the range increase of the twist of blades the rigid casing was changed by elastic elements that are located between the work basic ribs and provide the twist of blades to 28 degrees.

Also the twist mechanisms are updated that are located in the ribs and provide a reliable angle position of separate ribs by the beforehand determined values necessary for various values of the rotor diameter.

Experiments have been conducted for definition of the law of the air flow change along the blade span and the thrust force change at various diameters and speeds of the rotor rotation. A comparison analysis of the obtained results from the data of previous Projects has been conducted.

The results of conducted tests on the all Projects have been reported and approved at the authoritative international scientific and technological conferences and exhibitions; they are patented in proper time and published in scientific articles. In Georgia and Romania the monograph in Russian, Romanian and English has been published.

On the basis of multiple experiments it has been established that for the increase of the positioning precision of the movable parts of blades and by that of iteration of values of the rotor different diameters during various experiments it is expedient to change the hydro-system by mechanical transmissions. This solution also corresponds to the general tendencies recently in aviation according to which it is attempted to use a possibility of change of the hydro-system for mechanic.

On the basis of multiple experiments it has been established that for provision of softness of the blades surface at the big twists and increase of reliability of saving profiles at maximum loads it is necessary to decrease the length of elastic elements, i.e. to increase their number.

With this aim a calculation scheme has been compiled for definition of that optimal length of each elastic element at which the errors of violation of softness of the blades surface and the profile change at maximum values of twist will be within the admissible limits. It is established that if the number of elastic elements is increased to 7 instead of 4 then at the twist of one element within 4-5o one can obtain the general maximum twist of blade to 32-35o without violation of profiles in different sections. These are those values of twist that in its time were recommended by the Collaborators and other leading specialists. The preliminary aerodynamic calculations also show that the big value of twist is not required really as it won’t give any effect.

For the achievement of such values of twist new designs and mechanisms of control of angle positions of each supporting rib are recommended which in accordance with aerodynamic calculations change strictly according to the rotor diameter change.

With the aim of reduction of the blades movable parts and by that the values of centrifugal forces it is desirable to select the easier material for the elastic elements.

For this purpose several versions of setting-up of elastic elements and the technology of their manufacture from various modern materials have been elaborated.

There is also a definite reserve of reduction of weight in the fixture mechanism of the cable ends and in the mechanisms of the twist change.

The experiments have also shown that for increase of the positioning precision of the moving parts of blades and by that the iteration of various values of the rotor diameter at different experiments it is expedient to change the hydro-system with mechanical transmissions. This solution also corresponds to the general tendencies extended recently in aviation in accordance with which maximally is attempted to use the possibility of substitution of the hydro-system for mechanical.

For solution to these problems there are original designing solutions and interesting proposals that are suggested in the submitted Project.

This Project as the previous ones will conduce to the implementation of the ISTC objectives and tasks helping the scientists and specialists connected with weapon more orient their capabilities to the peaceful activities and also to their subsequent integration into the international scientific community. The Project will be conducive to the solution of national and international scientific and technical problems, particularly in organization of additional work places in the Republic and in creation of conditions on development of aviation without aerodromes.

The scope of activities is characterized by 8 basic tasks.

As in previous Projects in this Project the big and main role will be played by the Foreign Collaborators who are the most competent and well-known specialists in the field of aviation, particularly in experimental and designing aspects of helicopter technology. Therefore, they can take active part in a qualified expertise of new designing elaborations, in concrete definition of compilation of plans and methods for conduct of the necessary scientific experiments and in search of the newest information materials.

The technical approaches and methodology are conditioned by the fact that this Project relates to the category of demonstration of technologies. The scientific investigations and designing developments will be directed to the updating of the reliable mechanism of the VGR diameter change, combination with the system of compensation of centrifugal forces and the extension of the blade twist range change. This will give the possibility of development of such an approach of demonstration of new designs and technologies, which will conduce to the wide commercialization of the VGR.


The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.


ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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