Abstract: Farrell JL. (2013). Collision avoidance by speed change. International Journal of Unmanned Systems Engineering. 1(1): 1-8. With UAV usage increasing at rapid rates, a corresponding increase in attention to collision avoidance is clearly warranted. A strategy introduced more than ten years ago, being pursued in an investigation by Ohio University with NASA sponsorship, is supported by programming efforts that address dangerous scenarios. For aircraft that would collide if allowed to remain in their existing flight paths, conflict resolution can be provided by changing speed. Results are provided herein for a variety of conditions. The method requires no large budgets, nor new inventions; existing equipment (GPS/GNSS, ModeS) is sufficient with extension of known techniques (double differencing) to tracking. The approach offers enormous advantages in safety, versatility, autonomy, and all aspects of aircraft navigation performance. The theory has already been described in references cited; presentation of computational results here is followed by operational considerations. Preliminary flight testing recently reported elsewhere (Duan, Uijt de Haag, and Farrell; DASC 12, October 2012, Williamsburg, VA) raised prospects for reducing uncertainty volume (predicted position at time of closest approach) from hundreds of meters (due to m/s velocity uncertainty) to a few meters (from cm/s velocity accuracy)
