Airliner-UAV Flight Formation in Climb Regime

Extreme formation is a theoretical concept of selfsustain flight when a big airliner is followed by a small UAV glider flying in the airliner wake vortex. The paper presents results of a climb analysis with the goal to lift the gliding UAV to airliners cruise altitude. Wake vortex models, the UAV drag polar and basic parameters and airliner’s climb profile are introduced at first. Afterwards, flight performance of the UAV in a wake vortex is evaluated by analytical methods. Time history of optimal distance between an airliner and the UAV during a climb is determined. The results are encouraging. Therefore available UAV drag margin for electricity generation is figured out for different vortex models.

Authors:

• Pavel Zikmund
• Robert Popela

Keywords:

• Flight in formation
• self-sustained flight
• UAV
• wake vortex.

References:

[1] H. Weimerskirch, “Energy saving in flight formation,” in Nature, 413,
2001, pp. 697-698.
[2] R. J. Ray, “Flight test techniques used to evaluate performance benefits
during formation flight,” in NASA Conference publication, NASA, 1998.
[3] P. Zikmund, “Wake vortex gliding,” 6th EUCASS Conference, Krakow,
2015.
[4] “www.flightradar24.com/ (web page),” June 2015.
[5] T. M. Barrows, “Simplified methods of predicting aircraft rolling
moments due to vortex encounters,” in Journal of Aircraft, 1977, Vol.
14, No 5, pp. 434-439.
[6] C. W. Schwartz, K. U. Hahn, “Full-flight simulator study for wake
vortex hazard area investigation,” in Aerospace Science and Technology,
10/2006, pp. 136-143.
[7] J. D. Iversen, “Correlation of turbulent trailing vortex decay data,” Iowa
State University, 1976.
[8] M. J. Bhagwat, J. G. Leishman, “Generalized viscous vortex model for
application to free-vortex wake and aeroacoustics calculations,” in
Annual Forum Proceedings-American Helicopter Society, 2002, pp.
2042-2057.
[9] F. Holzäpfel, “Analysis of wake vortex decay mechanisms in the
atmosphere,” in Aerospace Science and Technology, July 2003, pp. 263-
275.
[10] F. Holzäpfel, “Probabilistic two-phase wake vortex decay and transport
model,” in Journal of Aircraft, 2003, Vol. 40, No 2, pp. 323-331.
[11] N. N. Ahmad, et al, “Review of idealized aircraft wake vortex models”,
AIAA paper, 2014.
[12] P. D. Delisi, “Aircraft wake vortex core size measurements,” AIAA
paper, pp. 1–9, 2003.
[13] M. Kóňa, “Aerodynamic design of transonic glider (Master thesis),”
Brno University of Technology, June 2015.
[14] J. Roskam, “Airplane Design VI: Preliminary calculation of
aerodynamic, thrust and power characteristics,” Kansas, Roskam
Aviation and Engineering Corp., 550 p, 1990.
[15] R. T. Whitcomb, “A study of the zero-lift drag-rise characteristics of
wing-body combinations near the speed of sound,” 1952.
[16] V. E. Lockwood, J. E. Fikes, “Control characteristics at transonic speeds
of a linked flap and spoiler on a tapered 45° sweptback wing of aspect
ratio 3,” NACA RM L52D25, 1952.