Gateway for:

Member Countries

Variable Geometry Rotor with Compensation of Centrifugal Forces


Controlled Variable Geometry Rotor with Centrifugal Force Compensation

Tech Area / Field

  • SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation

8 Project completed

Registration date

Completion date

Senior Project Manager
Gozal A

Leading Institute
Georgian Technical University, Georgia, Tbilisi


  • ONERA, France, Chatillon\nBoeing Defense & Space Group, USA, PA, Philadelphia\nBoeing Operations International, Inc., Russia, Moscow

Project summary

At the contemporary present stage of development of jet aviation there are still some fields of unchangeable expedient application of propeller driven aviation (helicopters, turbo-prop airplanes, compound helicopters).

The rotor, the diameter or geometry characteristics of blades can change during work, is determined as the variable geometry rotor (VGR). The very promising direction in development of optimal rotors is creation of rotors with variable diameter and blade twist during the flight.

The design of the rotor with fixed geometry is the result of non-optimal compromise between requirements, between the modes of takeoff and high speed of cruise flight. Takeoff is optimal at the big diameter and small twist and cruise flight is optimal at the small diameter and big twist. The optimality is in big payload capacity at takeoff and high maximum speed of cruise flight. The VGR is effective both for helicopters and airplanes. However, the VGR is especially effective for the airplanes with vertical takeoff and landing (VTOL) as the VTOL in point of fact work both in the mode of takeoff and cruise flight.

The objective of the project is the investigation and development of the rotor with controlled diameter change and blade twist during the flight with compensation of harmful influence of centrifugal forces.

The idea of application of the variable geometry rotors is not new. There are patents with various schemes of the rotor diameter change that could’t find a realization because of complexity of technical solutions, consideration of strengthens and reliability of inpidual units and parts. The problem of the variable geometry rotor (VGR) is not solved yet. In the USA the Boeing Company concentrated on the problem of the rotor blade twist, while the Sikorsky Company investigated the variable diameter rotor concept.

The project participants are competent in the above-mentioned field. They worked in course of the International Science and Technology Center (ISTC) on the project of the variable geometry rotor (VGR) and means of its control (actuators). The results of the project were the following.

The original variable geometry rotor (VGR) with combinations of variable diameter and twist during the flight has been created. The approach priority is protected by the Patents of the Russian Federation and Georgia, the authors of which are participants of the project. The control mechanism units of the rotor diameter and twist change have been developed. The versatile program of the VGR tests on the especially designed test stand has been carried out. The tensometric and dynamometric measurements of the rotor thrust at simulation of takeoff have been conducted.

The VGR stand tests showed that at high rotational numbers the significant centrifugal forces arise that influence on the blade movable part. They are taken by the most loaded element of the VGR design, the jackscrew that at the same time is its weakest unit. Therefore, the reduction of harmful influence of these forces is the actual problem. The solution to this problem will open the ways of practical application of the VGR to the flying vehicles.

Various versions of compensation of influence of centrifugal forces have been considered up to use of ballast loads and mechanical springs, but the most optimal we consider the application of hydro-accumulated system.

The investigation and development of the variable geometry rotor (VGR) with compensation of influence of centrifugal forces on the basis of the hydro-accumulating system will be conducted in the project. Various versions will be considered and the most optimal of them will be manufactured for stand tests. The earlier developed and manufactured test stand within the previous project will be fundamentally modernized with the aim not only simulation of takeoff but also cruise flight and what is especially significant for the conversion mode from takeoff to the cruise flight. Besides that, the stand will be used for aerodynamic investigations as well.

The presented project as the previous one will be conducive for implementation of the ISTC objectives and tasks help the scientists and specialists connected with weapon to orientate their capabilities to the peaceful activities and also to integrate them into the international scientific community. The project will be conducive to solution to national and international scientific and technical problems, particularly, development of aviation without aerodromes.

The scope of activities is characterized with 10 tasks with corresponding subtasks beginning with the formation of the concept and ending with the fabrication of the VGR with the stand aerodynamic investigations.

As in the previous project in the present project the big and significant role will be played by Mr.Leo Dadone, the foreign collaborator, responsible for advanced research programs of the Boeing Company (USA), with extensive experience in the experimental and design aspects of rotorcraft technology, the manager of the most experimental and designing works in helicopter construction. As in the previous project Mr.Leo Dadone takes part in concrete definition of plans, specific designing developments and information search.

Technical approach and methodology are conditioned with the fact that the present project relates to the category of applied investigations. During the consideration of alternative versions the euristic methods (brain storm, morphological analysis) will be used in combination with computer investigations, and at stand and aerodynamic investigations, planning of experiments.


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.

Promotional Material

Значимы проект

See ISTC's new Promotional video view