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Designing and producing a bird-inspired unmanned sailplane

Göksel Keskin (Department of Biology, Eskisehir Osmangazi University, Eskisehir, Turkey)
Seyhun Durmus (Edremit School of Civil Aviation, Balikesir Universitesi, Balikesir, Turkey)
Muharrem Karakaya (Department of Biology, Eskisehir Osmangazi University, Eskisehir, Turkey)
Melih Cemal Kushan (Department of Aeronautical Engineering, Eskisehir Osmangazi University, Eskisehir, Turkey)

Aircraft Engineering and Aerospace Technology

ISSN: 0002-2667

Article publication date: 16 July 2021

Issue publication date: 12 August 2021




Increasing endurance was a very appropriate subject for the biomimetic approach. The study aims to design and manufacture a long-lasting mini unmanned aerial vehicle (UAV) using active gliding and soaring.


The endurance of mini UAVs is limited by battery or fuel capacity, and it is not always possible to increase these energy sources due to the fuselage size. Long endurance aircraft are required in various areas such as silent environment and traffic monitoring or search and rescue. Literature research on bird flight performance conducted to determine design parameters. These parameters are used in the theoretical design of the UAV for optimization. Computational fluid dynamics simulation and flight tests of the UAV performed to figure out the success of the design.


For a mini UAV to be produced in this class, it has been observed that it is more accurate to examine birds instead of gliders due to the size similarity. The UAV design reaches a 27.5 L/D (Glide ratio) ratio in the theoretical approach. However, flight results approved max L/D ratio is around 25 at the sea level. This flight performance is enough to outperform in glide ratio of Wandering albatrosses.

Practical implications

Sailplanes are known as sport aircraft. However, recent projects focus on glider designs due to fuel efficiency and silent tracking. Stemme S-14 that carries a high-resolution camera is one of the examples of these projects. The unmanned glider design can lead to these implications in the UAVs at least during the stand-by period in the air. Thanks to low weight, UAVs do not require strong thermals, which allows flying almost all over the world.


Researchers generally focus on increasing the battery capacity or the performance of the UAV. However, this study’s concentration is to increase the flight duration of the UAV by using geographical currents. For this purpose, taking advantage of bird morphology is quite a new topic. Also, glider type designs are rarely found in the field.



This work was supported by Eskişehir Osmangazi University Scientific Research Project Commission under Grant 2018–2245 coded project.


Keskin, G., Durmus, S., Karakaya, M. and Kushan, M.C. (2021), "Designing and producing a bird-inspired unmanned sailplane", Aircraft Engineering and Aerospace Technology, Vol. 93 No. 6, pp. 1052-1059.



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