Stalling of Helicopter Blades

Stalling of Helicopter Blades PDF

Author: F. B. Gustafson

Publisher:

Published: 1946

Total Pages: 22

ISBN-13:

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Theoretical studies have predicted that operation of a helicopter rotor beyond certain combinations of thrust, forward speed, and rotational speed might be prevented by rapidly increasing stalling of the retreating blade. The same studies also indicate that the efficiency of the rotor will increase unitl these limits are reached or closely approached, so that it is desirable to design helicopter rotors for operation close to the limits imposed by blade stalling. Inasmuch as the theoretical predictions of blade stalling involve numerous approximations and assuptions of blade stalling, an experimental investigation was needed to determine whether, in actual practice, the stall did occur and spread as predicted and to establish the amount of stalling that could be present without severe vibration or control difficulties being introduced.

Cyclic and Collective

Cyclic and Collective PDF

Author: Shawn Coyle

Publisher: Lulu.com

Published: 2009

Total Pages: 538

ISBN-13: 0557090660

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Possibly the most complete book written to date on helicopters and helicopter flying. Covers subjects not covered by other manuals such as turbine engines, performance, flight manuals, automatic flight controls, legal aspects, introductory stability and control and multi-engine helicopters.

Analysis of Stall Flutter of a Helicopter Rotor Blade

Analysis of Stall Flutter of a Helicopter Rotor Blade PDF

Author: Peter Crimi

Publisher:

Published: 1973

Total Pages: 138

ISBN-13:

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A study of rotor blade aeroelastic stability was carried out, using an analytic model of a two-dimensional airfoil undergoing dynamic stall and an elastomechanical representation including flapping, flapwise bending and torsional degrees of freedom. Results for a hovering rotor demonstrated that the models used are capable of reproducing both classical and stall flutter. The minimum rotor speed for the occurrence of stall flutter in hover, was found to be determined from coupling between torsion and flapping. Instabilities analogous to both classical and stall flutter were found to occur in forward flight. However, the large stall-related torsional oscillations which commonly limit aircraft forward speed appear to be the response to rapid changes in aerodynamic moment which accompany stall and unstall, rather than the result of an aeroelastic instability. The severity of stall-related instabilities and response was found to depend to some extent on linear stability. Increasing linear stability lessens the susceptibility to stall flutter and reduced the magnitude of the torsional response to stall and unstall.

Special Opportunities in Helicopter Aerodynamics

Special Opportunities in Helicopter Aerodynamics PDF

Author: W. J. McCroskey

Publisher:

Published: 1983

Total Pages: 38

ISBN-13:

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Aerodynamic research relating to modern helicopters includes the study of three-dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomenon that hamper the development of satisfactory engineering prediction techniques, but which provides a rich source of research opportunities: flow separations, compressibility effects, complex vortical wakes, and aerodynamic interference between components. Several examples of work in progress are given, including dynamic stall alleviation, the development of computational methods for transonic flow, rotor-wake predictions, and blade-vortex interactions. (Author).

New Results in Numerical and Experimental Fluid Mechanics XII

New Results in Numerical and Experimental Fluid Mechanics XII PDF

Author: Andreas Dillmann

Publisher: Springer Nature

Published: 2019-09-26

Total Pages: 867

ISBN-13: 3030252531

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This book gathers contributions to the 21st biannual symposium of the German Aerospace Aerodynamics Association (STAB) and the German Society for Aeronautics and Astronautics (DGLR). The individual chapters reflect ongoing research conducted by the STAB members in the field of numerical and experimental fluid mechanics and aerodynamics, mainly for (but not limited to) aerospace applications, and cover both nationally and EC-funded projects. Special emphasis is given to collaborative research projects conducted by German scientists and engineers from universities, research-establishments and industries. By addressing a number of cutting-edge applications, together with the relevant physical and mathematics fundamentals, the book provides readers with a comprehensive overview of the current research work in the field. The book’s primary emphasis is on aerodynamic research in aeronautics and astronautics, and in ground transportation and energy as well.

Principles of Helicopter Aerodynamics with CD Extra

Principles of Helicopter Aerodynamics with CD Extra PDF

Author: Gordon J. Leishman

Publisher: Cambridge University Press

Published: 2006-04-24

Total Pages: 860

ISBN-13: 9780521858601

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Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.

A Method for Analyzing Dynamic Stall of Helicopter Rotor Blades

A Method for Analyzing Dynamic Stall of Helicopter Rotor Blades PDF

Author: Peter Crimi

Publisher:

Published: 1972

Total Pages: 116

ISBN-13:

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A model for each of the basic flow elements involved in the unsteady stall of a two-dimensional airfoil in incompressible flow is presented. The interaction of these elements is analyzed using a digital computer. Computations of the loading during transient and sinusoidal pitching motions are in good qualitative agreement with measured loads. The method was used to confirm that large torsional response of helicopter blades detected in flight tests can be attributed to dynamic stall.

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