Dynamic Sensitivity to Atmospheric Turbulence of Unmanned Air Vehicles with Varying Configuration

Abstract

DOI: 10.2514/1.46860 Air vehicle flight in turbulence is generally treated as an anomalous part of the flying environment. Aircraft geometries and flight-control systems are often designed and tested for calm atmospheric conditions, where both steady winds and gusts are minor. As a result, the flight performance of small aircraft deteriorates in the presence of atmospheric turbulence, where gust disturbances can be large relative to the flying speeds. A better approach is needed in the aircraft and control system design process that specifically accounts for the effects of turbulence and providesameansofmitigatingdisturbancestoimprovethemissioneffectivenessofmicrounmannedairvehiclesand small unmanned air vehicles. The current research considers untethered flight tests of a small unmanned air vehicle in a large wind engineering tunnel that can be configured to replicate turbulence levels expected from urban and suburban environments. Systematic changes to the configuration of the fixed-wing aircraft are made to evaluate the roleofmetrics,suchasc.g.,mass,momentofinertia,wingspan,andwingloadingtoturbulencesensitivity.Estimates of the force and moment disturbances indicate that some parameters, such as moment of inertia, have simple and expectedinfluencesontheresponsetoturbulence. Conversely,wingareaandmasshaveconflictingeffectsduetothe compounded influences on the aircraft response. The sensitivity of the various aircraft configurations to turbulence are presented as control equivalent turbulence disturbances, which equate forces and moments acting on the airframe to control deflections. This method normalizes the aircraft responses with respect to the ability to suppress disturbances with actuated controls.