Assessing formation flight benefits on trajectory level including turbulence and gust

Abstract

Within this paper two methods to estimate the aerodynamic benefits of a two-aircraft formation will be compared. The first model calculates the average up-wash velocity at the follower’s wing resulting from the leaders wake and superimposes it on the aircraft speed during the trajectory calculation. The second model uses a vortex lattice method to model the aerodynamic interactions between the leader and the follower for a set of specific flight states beforehand. This database can be used by the trajectory calculation to interpolate the actual benefits for the given flight. In this paper for a specific aircraft type and an example mission both methods will be compared and it will be shown, that they can be used to derive surrogate models to predict the formation benefits based on general formation data. To further improve the prediction of the aerodynamic benefits, the influence of gust and turbulence will be assessed by simulating the aircraft reaction on the disturbances and deriving a reduction factor degrading the aerodynamic benefits creating a database and corresponding surrogate models. The occurrence of turbulence and gust can then stochastically be imposed during the trajectory calculation and the sensitivity of the aerodynamic benefits will be examined.