## 5 Conclusions and Future Works  
This paper presents a real and practical case of a transformation of a fixed-wing unmanned aerial system, used as an aerial target and powered by an internal combustion engine, in an electric RPA for use in the cultivation of olive trees and other species that occupy large areas of land. Similarly, and taking advantage of one of the main characteristics of electric airplanes, such as its low-noise level, this electric RPA could be used in protected environments, such as natural parks, for the surveillance and supervision of different animal species.  
The main reason for carrying out this transformation is to increase the flight autonomy of the RPA in order to be able to take measurements of the different parameters that affect a large-scale crop. This purpose was achieved by increasing the range by almost 50% compared with the ICE model, and much more if it is compared with the electric multicopters actually used in the project TecnOlivo. The payload was reduced but the increase in flight autonomy compensates this decrease. If compared with other commercial electric fixed-wing UAVs (Table 12), it can be realized that new features of the electric ALO can be compared with them, even improving them in most of the cases.  
On the other hand, the present work is an intermediate step to complete an RPA that is moved with hydrogen. Future works on this aerial platform will consist of replacing some of the batteries on board with a hydrogen-based system and fuel cells. In this way it is intended to further increase the autonomy of the UAV [89; 90]. The INTA laboratory has vast experience (since 1990) in hydrogen technology and fuel cells and this is not the first RPAS built at INTA based on hydrogen and fuel cells [91]. Thus, in the following months, a new RPA with hydrogen on board will be flying across the sky.  
Figure 27: Electric ALO unmanned aerial vehicle ready to fly.  
**Author Contributions:** Conceptualization, F.I.L., A.F.B. and J.A.B.; Methodology, F.I.L., F.S. and J.M.A.; Software, A.F.B. and J.A.B; Validation, F.I.L., A.F.B. and J.A.B.; Formal Analysis, F.I.L., A.F.B. and J.A.B.; Investigation, F.I.L., A.F.B. and J.A.B.; Resources, F.I.L., A.F.B., J.A.B., F.S. and J.M.A.; Data Curation, A.F.B. and J.A.B.; Writing - Original Draft Preparation, F.I.L.; Writing - Review & Editing, all; Visualization, F.I.L.; Supervision, F.S. and J.M.A.; Project Administration, F.I.L.; Funding Acquisition, F.I.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** Part of this work was supported by \"Tecnologias para el manejo y supervision del cultivo del olivo (Tecnolivo)\", a project of the program Interreg V-A Espana-Portugal (POCTEP 2014-2020) and was co-funded by FEDER (0115_TECNOLIVO_6_E).  
**Acknowledgments:** The authors would like to thank [PERSON] for his helpful advice in various technical issues regarding the testing platform.  
**Conflicts of Interest:** The authors declare no conflicts of interest.  
**List of Acronyms**  
BMS Battery management system  
CAN Controller area network  
ESC Electronic speed controller  
DSM Digital surface models  
FCS Flight control system  
FLIR Forward-looking infrared  
GCS Ground control station  
HP Horse power  
ICE Internal combustion engine  
IGBT Insulated gate bipolar transistor  
LiPo lithium-ion polymer  
MOSFET Metal-oxide-semiconductor field-effect transistor  
NIR Near infrared  
NGFCS Navigation guidance and flight control systems  
NTC Negative temperature coefficient  
PWM pulse-width modulation  
RGB Read green blue  
RPA Remotely piloted aircraft  
RPAS Remotely piloted aircraft system  
Rpm Revolutions per minute  
SOC State of charge  
UART Universal asynchronous receiver-transmitter  
UAS Unmanned aerial system  
UAV Unmanned aerial vehicles