Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics (Paperback) (ISBN-13: 9781287237013)

The influence of vortex ring state (VRS) on rotorcraft flight dynamics is investigated, specifically the vertical velocity drop of helicopters and the roll-off of tiltrotors encountering VRS. The available wind tunnel and flight test data for rotors in vortex ring state are reviewed. Test data for axial flow, non-axial flow, two rotors, unsteadiness, and vortex ring state boundaries are described and discussed. Based on the available measured data, a VRS model is developed. The VRS model is a parametric extension of momentum theory for calculation of the mean inflow of a rotor, hence suitable for simple calculations and real-time simulations. This inflow model is primarily defined in terms of the stability boundary of the aircraft motion. Calculations of helicopter response during VRS encounter were performed, and good correlation is shown with the vertical velocity drop measured in flight tests. Calculations of tiltrotor response during VRS encounter were performed, showing the roll-off behavior characteristic of tiltrotors. Hence it is possible, using a model of the mean inflow of an isolated rotor, to explain the basic behavior of both helicopters and tiltrotors in vortex ring state.

Author: Nasa Technical Reports Server (Ntrs), Wayne Johnson
ISBN-10: 1287237010
ISBN-13: 9781287237013
Publisher: Bibliogov
Language: English
Published: 07/23/2013
Pages: 80
Format: Paperback
Weight: 0.35lbs
Size: 9.69h x 7.44w x 0.17d