Wake Vortex Detection and Tracking for Aircraft Formation Flight

Abstract

In a fuel-efficient extended formation flight of commercial airplanes, the aerodynamic benefits depend on one’s ability to surf wake vortices. This paper presents a wake vortex detection scheme based on the exploitation of the aircraft flight dynamics measurements that effectively enables wake surfing. The study focuses on a two-aircraft formation where the follower senses, successfully locates, and tracks the wake produced by the leader over time. The proposed approach relies on an ensemble Kalman filter that propagates a surrogate model of the formation. The model output is here corrected within the estimator through a comparison with measurements of the full six-degree-of-freedom dynamics of the follower, as well as geometric characteristics of the leader. This essentially waives the need for dedicated hardware devices and only requires episodic communication between the leader and the follower. The efficiency of the novel detection strategy is demonstrated using reference data obtained from large-eddy simulations. It is found that the chosen combination of estimator and dynamics measurements is sufficient to detect the position of the impacting wake as long as the dynamics are accurately reproduced by the surrogate model. Additionally, it is shown that a lack of observability hinders the concurrent estimation of the wake position and strength in the presence of uncertainty. Finally, a simulation case evaluates the fuel savings that an active tracking strategy of the optimal relative positioning provides compared with a wake-independent positioning.