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TsAGI specialists present latest rotary-wing aircraft technology
This past January, scientists at the Central AeroHydrodynamic Institute named after professor N. E. Zhukovsky (TsAGI, a part of the Scientific Research Center “Institute named after N. E. Zhukovsky”) discussed pressing helicopter construction issues at a meeting held during a research workshop of the Division for Helicopter Aerodynamics and Dynamics, Aircraft High-Angle Spins and Aerodynamics.

The Institute’s specialists showcased their studies of rotary-wing aircraft with those related to high-speed helicopters among them, with a case study of a layout of a rotary-wing aircraft with an in-flight stoppable main rotor-wing being an example. Valery Gorban, Lead Engineer at the Division for Helicopter Aerodynamics and Dynamics, Aircraft High-Angle Spins and Aerodynamics, elaborated on these studies in his speech.

Valery Gorban explained: “The traditional design of the main rotor implies serious limitations on velocity capacities of a helicopter. An efficient solution to this problem could be an in-flight stoppable main rotor-wing. During vertical take-off, it operates as a regular main rotor, but then, after building up a certain speed, the rotor stops and then operates as a traditional aircraft wing, thus providing for a sufficient increase in the flight velocity. One major obstacle in implementation of this scheme is providing required levels of stability and controllability of an aircraft at the moment of transition between the ‘helicopter’ and ‘aircraft’ modes and vice versa. At TsAGI, we’ve developed several engineering solutions which will supposedly eliminate the problem in question.” Last fall, tests were run in the Insitute’s free-spinning wind tunnel successfully proving the capacity of the main rotor system with a stoppable rotor-wing to maintain stable and efficient work during such transition stages. Use of this concept, according to preliminary assessments by specialists, may increase the maximum flight velocity of a helicopter from 400 to 600–700 kph.

Another solution for building high-speed single-rotor helicopters with a hinged rotor was introduced in the speech made by Evgeny Borisov, Deputy Head of the Division for Helicopter Aerodynamics and Dynamics, Aircraft High-Angle Spins and Aerodynamics. He gave a talk on the helicopter’s main rotor studies with back-staggered flapping hinges. “In many cases, flap vortex on retreating main rotor blades is the main adverse factor in increasing the flight velocity of a single-rotor helicopter, since it leads to degradation of aerodynamic characteristics of the rotor, abrupt increase of load in the control system, and growth of helicopter vibration,” Borisov explained. “The most effective solution for the flap vortex issue is use of various methods for increasing the aerodynamic load on advancing blades and reducing it on those retreating.” As he explained, load increase on advancing blades and decrease on retreating blades causes an increase in the lateral moment of the helicopter, which raises a need for extra solutions to account for it. A brand new concept of the main rotor with back-staggered flapping hinges brought up by TsAGI allows balancing a single-rotor helicopter at high flight velocities without additional design solutions.

The R&D workshop on helicopter construction is held regularly, twice per month. The event is conducted by TsAGI and takes place in the Division for Helicopter Aerodynamics and Dynamics, Aircraft High-Angle Spins and Aerodynamics. Members of Kamov JSC, Mil Moscow Helicopter Plant JSC, and other companies specialized in helicopter R&D are invited to participate in our workshops.

Source: TsAGI.

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