Understanding effect of blade flexibility on cycloidal rotor hover performance Conference Paper uri icon


  • Copyright 2015 by the American Helicopter Society International, Inc. All rights reserved. In this paper, the aeromechanics of a cycloidal rotor (or cyclorotor) is investigated to understand the effect of blade flexibility on hover performance of the rotor. Towards this, experiments were conducted on cyclorotors using moderately and highly flexible blades and rotor performance was measured in terms of net thrust and power requirement. These studies showed that with increasing blade flexibility the rotor thrust decreases, whereas, the power consumption increases leading to a significant drop in power loading (thrust/power). To investigate these phenomena, a coupled aeroelastic model of cyclorotor has been developed and systematically validated with experimental results. Aeroelastic model consists of an unsteady indicial aerodynamics model coupled with a geometrically exact beam-based structural model. In comparison with a second-order nonlinear structural model inclusion of a geometrically exact model proved to be essential in accurate prediction of rotor performance, especially while using highly flexible blades. Based on a systematic analysis performed using the validated model it was observed that the large torsional deflections of the blades produced by the transverse centrifugal loads is the key reason for drop in thrust. The torsional deflections occur from two sources which are, (1) moment produced directly by the centrifugal force because of the offset between the chordwise elastic axis and center of gravity location, and (2) non-linear moment created by the radial and tangential bending curvatures. Because of this non-linear moment, the reduction of bending stiffness also increased torsional deflections, which led to a reduction in thrust.

published proceedings

  • American Helicopter Society International - AHS Specialists' Conference on Aeromechanics Design for Vertical Lift 2016

author list (cited authors)

  • Haider, A., & Benedict, M.

complete list of authors

  • Haider, A||Benedict, M

publication date

  • January 2016