A Physics-Based Model of Rotorcraft Brownout for Flight Simulation Applications

Rotorcraft brownout, which is caused by the entrainment of dust and ground debris by the rotorwash during take-off and landing, is a critical rotorcraft operational problem. Brownout has accounted for a significant number of military helicopter accidents in Iraq and Afghanistan. Brownout operations affect safe handling due to the reduction of visibility, in addition to potentially leading to severely damaged engine components and rotor blades. This paper describes the development of a physics-based aerodynamic analysis suitable for engineering simulation of rotorcraft brownout conditions. Central to the brownout analysis is a comprehensive free-wake and fast panel model to predict the rotorwash flow field in close proximity to the ground, which is used to drive debris particle entrainment/transport and visual obscuration models to predict the degraded visual environment. Once completed, this analysis may be coupled with any flight simulation environment. Results are presented demonstrating the ability to predict the rotorwash field in near ground operations, as well as qualitative visualization of the brownout encounter in a visual simulation environment.