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Record Details

Record 86 of 11471
Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics
External Online Source: http://handle.dtic.mil/100.2/ADA526709
Author and Affiliation:
Johnson, Wayne(Army Aviation and Missile Command, NASA Rotorcraft Div., Moffett Field, CA, United States)
Abstract: 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, nonaxial 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.
Publication Date: Jan 01, 2004
Document ID:
20100033458
(Acquired Sep 28, 2010)
Subject Category: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
Report/Patent Number: AD-A526709
Document Type: Technical Report
Meeting Information: AHS 4th Decennial Specialist's Conference on Aeromechanics; 21-23 Jan. 2004; San Francisco, CA; United States
Meeting Sponsor: American Helicopter Society, Inc.; United States
Financial Sponsor: NASA Ames Research Center; Moffett Field, CA United States
Organization Source: Army Aviation and Missile Command; NASA Rotorcraft Div.; Moffett Field, CA, United States
Description: 62p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: AERODYNAMICS; HELICOPTERS; ROTARY WING AIRCRAFT; TILT ROTOR AIRCRAFT; VORTEX RINGS; AXIAL FLOW; FLIGHT TESTS; MOMENTUM; REAL TIME OPERATION; STABILITY; VORTICES; WIND TUNNELS
Other Descriptors: HELICOPTERS; TILT ROTOR AIRCRAFT; REAL TIME; VORTICES; AXIAL FLOW; WIND TUNNELS; MOMENTUM; STABILITY; FLIGHT TESTING; VORTEX RING STATE
Availability Source: Other Sources
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