TY  - JOUR
A1  - Götten, Falk
A1  - Finger, Felix
A1  - Havermann, Marc
A1  - Braun, Carsten
A1  - Marino, M.
A1  - Bil, C.
T1  - Full configuration drag estimation of short-to-medium range fixed-wing UAVs and its impact on initial sizing optimization
JF  - CEAS Aeronautical Journal
N2  - The paper presents the derivation of a new equivalent skin friction coefficient for estimating the parasitic drag of short-to-medium range fixed-wing unmanned aircraft. The new coefficient is derived from an aerodynamic analysis of ten different unmanned aircraft used for surveillance, reconnaissance, and search and rescue missions. The aircraft is simulated using a validated unsteady Reynolds-averaged Navier Stokes approach. The UAV’s parasitic drag is significantly influenced by the presence of miscellaneous components like fixed landing gears or electro-optical sensor turrets. These components are responsible for almost half of an unmanned aircraft’s total parasitic drag. The new equivalent skin friction coefficient accounts for these effects and is significantly higher compared to other aircraft categories. It is used to initially size an unmanned aircraft for a typical reconnaissance mission. The improved parasitic drag estimation yields a much heavier unmanned aircraft when compared to the sizing results using available drag data of manned aircraft.
KW  - Parasitic drag
KW  - UAV
KW  - CFD
KW  - Aircraft sizing
Y1  - 2021
U6  - https://doi.org/10.1007/s13272-021-00522-w
SN  - 1869-5590 (Online)
SN  - 1869-5582 (Print)
N1  - Corresponding author: Falk Götten
VL  - 12
SP  - 589
EP  - 603
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Finger, Felix
A1  - Braun, Carsten
A1  - Bil, Cees
T1  - Comparative assessment of parallel-hybrid-electric propulsion systems for four different aircraft
JF  - Journal of Aircraft
N2  - Until electric energy storage systems are ready to allow fully electric aircraft, the combination of combustion engine and electric motor as a hybrid-electric propulsion system seems to be a promising intermediate solution. Consequently, the design space for future aircraft is expanded considerably, as serial hybrid-electric, parallel hybrid-electric, fully electric, and conventional propulsion systems must all be considered. While the best propulsion system depends on a multitude of requirements and considerations, trends can be observed for certain types of aircraft and certain types of missions. This Paper provides insight into some factors that drive a new design toward either conventional or hybrid propulsion systems. General aviation aircraft, regional transport aircraft vertical takeoff and landing air taxis, and unmanned aerial vehicles are chosen as case studies. Typical missions for each class are considered, and the aircraft are analyzed regarding their takeoff mass and primary energy consumption. For these case studies, a high-level approach is chosen, using an initial sizing methodology. Only parallel-hybrid-electric powertrains are taken into account. Aeropropulsive interaction effects are neglected. Results indicate that hybrid-electric propulsion systems should be considered if the propulsion system is sized by short-duration power constraints. However, if the propulsion system is sized by a continuous power requirement, hybrid-electric systems offer hardly any benefit.
Y1  - 2020
U6  - https://doi.org/10.2514/1.C035897
SN  - 1533-3868
VL  - 57
IS  - 5
PB  - AIAA
CY  - Reston, Va.
ER  -