text: abstract— in this paper we propose an algorithm for stabilizing circular formations of fixed-wing uavs with constant
  speeds. the algorithm is based on the idea of tracking circles
  with different radii in order to control the inter-vehicle phases
  with respect to a target circumference. we prove that the
  desired equilibrium is exponentially stable and thanks to the
  guidance vector field that guides the vehicles, the algorithm
  can be extended to other closed trajectories. one of the main
  advantages of this approach is that the algorithm guarantees
  the confinement of the team in a specific area, even when
  communications or sensing among vehicles are lost. we show
  the effectiveness of the algorithm with an actual formation flight
  of three aircraft. the algorithm is ready to use for the general
  public in the open-source paparazzi autopilot.