@inproceedings{FingerGoettenBraunetal.2019,
  author    = {Finger, Felix and G{\"o}tten, Falk and Braun, Carsten and Bil, Cees},
  title     = {Mass, Primary Energy, and Cost - The Impact of Optimization Objectives on the Initial Sizing of Hybrid-Electric General Aviation Aircraft},
  series = {Deutscher Luft- und Raumfahrtkongress 2019, DLRK 2019. Darmstadt, Germany},
  booktitle = {Deutscher Luft- und Raumfahrtkongress 2019, DLRK 2019. Darmstadt, Germany},
  doi       = {10.25967/490012},
  pages     = {1 -- 17},
  year      = {2019},
  language  = {en}
}
@inproceedings{GoettenFinger2019,
  author    = {G{\"o}tten, Falk and Finger, Felix},
  title     = {Conceptual Design of a Modular 150 kg Vertical Take-off and Landing Unmanned Aerial Vehicle},
  series = {Deutscher Luft- und Raumfahrtkongress - DLRK 2019. Darmstadt, Germany},
  booktitle = {Deutscher Luft- und Raumfahrtkongress - DLRK 2019. Darmstadt, Germany},
  pages     = {1 -- 10},
  year      = {2019},
  language  = {en}
}
@article{FingerGoettenBraunetal.2020,
  author    = {Finger, Felix and G{\"o}tten, Falk and Braun, Carsten and Bil, Cees},
  title     = {Mass, primary energy, and cost: the impact of optimization objectives on the initial sizing of hybrid-electric general aviation aircraft},
  series = {CEAS Aeronautical Journal},
  volume    = {2020},
  journal   = {CEAS Aeronautical Journal},
  number    = {11},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1869-5590},
  doi       = {10.1007/s13272-020-00449-8},
  pages     = {713 -- 730},
  year      = {2020},
  abstract  = {For short take-off and landing (STOL) aircraft, a parallel hybrid-electric propulsion system potentially offers superior performance compared to a conventional propulsion system, because the short-take-off power requirement is much higher than the cruise power requirement. This power-matching problem can be solved with a balanced hybrid propulsion system. However, there is a trade-off between wing loading, power loading, the level of hybridization, as well as range and take-off distance. An optimization method can vary design variables in such a way that a minimum of a particular objective is attained. In this paper, a comparison between the optimization results for minimum mass, minimum consumed primary energy, and minimum cost is conducted. A new initial sizing algorithm for general aviation aircraft with hybrid-electric propulsion systems is applied. This initial sizing methodology covers point performance, mission performance analysis, the weight estimation process, and cost estimation. The methodology is applied to the design of a STOL general aviation aircraft, intended for on-demand air mobility operations. The aircraft is sized to carry eight passengers over a distance of 500 km, while able to take off and land from short airstrips. Results indicate that parallel hybrid-electric propulsion systems must be considered for future STOL aircraft.},
  language  = {en}
}
@article{FingerBraunBil2020,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Impact of Battery Performance on the Initial Sizing of Hybrid-Electric General Aviation Aircraft},
  series = {Journal of Aerospace Engineering},
  volume    = {33},
  journal   = {Journal of Aerospace Engineering},
  number    = {3},
  publisher = {ASCE},
  address   = {Reston, Va.},
  issn      = {1943-5525},
  doi       = {10.1061/(ASCE)AS.1943-5525.0001113},
  year      = {2020},
  abstract  = {Studies suggest that hybrid-electric aircraft have the potential to generate fewer emissions and be inherently quieter when compared to conventional aircraft. By operating combustion engines together with an electric propulsion system, synergistic benefits can be obtained. However, the performance of hybrid-electric aircraft is still constrained by a battery's energy density and discharge rate. In this paper, the influence of battery performance on the gross mass for a four-seat general aviation aircraft with a hybrid-electric propulsion system is analyzed. For this design study, a high-level approach is chosen, using an innovative initial sizing methodology to determine the minimum required aircraft mass for a specific set of requirements and constraints. Only the peak-load shaving operational strategy is analyzed. Both parallel- and serial-hybrid propulsion configurations are considered for two different missions. The specific energy of the battery pack is varied from 200 to 1,000 W⋅h/kg, while the discharge time, and thus the normalized discharge rating (C-rating), is varied between 30 min (2C discharge rate) and 2 min (30C discharge rate). With the peak-load shaving operating strategy, it is desirable for hybrid-electric aircraft to use a light, low capacity battery system to boost performance. For this case, the battery's specific power rating proved to be of much higher importance than for full electric designs, which have high capacity batteries. Discharge ratings of 20C allow a significant take-off mass reduction aircraft. The design point moves to higher wing loadings and higher levels of hybridization if batteries with advanced technology are used.},
  language  = {en}
}
@inproceedings{FingerGoettenBraunetal.2019,
  author    = {Finger, Felix and G{\"o}tten, Falk and Braun, Carsten and Bil, Cees},
  title     = {Cost Estimation Methods for Hybrid-Electric General Aviation Aircraft},
  series = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  booktitle = {Asia Pacific International Symposium on Aerospace Technology. APISAT 2019},
  pages     = {1 -- 13},
  year      = {2019},
  language  = {en}
}
@inproceedings{FingerBraunBil2020,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Comparative assessment of parallel-hybrid-electric propulsion systems for four different aircraft},
  series = {AIAA Scitech 2020 Forum},
  booktitle = {AIAA Scitech 2020 Forum},
  doi       = {10.2514/6.2020-1502},
  pages     = {15 Seiten},
  year      = {2020},
  abstract  = {As battery technologies advance, electric propulsion concepts are on the edge of disrupting aviation markets. However, 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-, parallel-hybrid-, 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 towards either conventional or hybrid propulsion systems. General aviation aircraft, VTOL air taxis, transport aircraft, and UAVs are chosen as case studies. Typical missions for each class are considered, and the aircraft are analyzed regarding their take-off mass and primary energy consumption. For these case studies, a high-level approach is chosen, using an initial sizing methodology. Results indicate that hybrid-electric propulsion systems should be considered if the propulsion system is sized by short-duration power constraints (e.g. take-off, climb). However, if the propulsion system is sized by a continuous power requirement (e.g. cruise), hybrid-electric systems offer hardly any benefit.},
  language  = {en}
}
@inproceedings{GoettenFingerMarinoetal.2019,
  author    = {G{\"o}tten, Falk and Finger, Felix and Marino, Matthew and Bil, Cees and Havermann, Marc and Braun, Carsten},
  title     = {A review of guidelines and best practices for subsonic aerodynamic simulations using RANS CFD},
  series = {Asia-Pacific International Symposium on Aerospace Technology (APISAT), At Gold Coast, Australia, 04. - 06. Dezember 2019},
  booktitle = {Asia-Pacific International Symposium on Aerospace Technology (APISAT), At Gold Coast, Australia, 04. - 06. Dezember 2019},
  isbn      = {978-1-925627-40-4},
  pages     = {19 Seiten},
  year      = {2019},
  language  = {de}
}
@inproceedings{FingerdeVriesVosetal.2020,
  author    = {Finger, Felix and de Vries, Reynard and Vos, Roelof and Braun, Carsten and Bil, Cees},
  title     = {A comparison of hybrid-electric aircraft sizing methods},
  series = {AIAA Scitech 2020 Forum},
  booktitle = {AIAA Scitech 2020 Forum},
  doi       = {10.2514/6.2020-1006},
  pages     = {31 Seiten},
  year      = {2020},
  abstract  = {The number of case studies focusing on hybrid-electric aircraft is steadily increasing, since these configurations are thought to lead to lower operating costs and environmental impact than traditional aircraft. However, due to the lack of reference data of actual hybrid-electric aircraft, in most cases, the design tools and results are difficult to validate. In this paper, two independently developed approaches for hybrid-electric conceptual aircraft design are compared. An existing 19-seat commuter aircraft is selected as the conventional baseline, and both design tools are used to size that aircraft. The aircraft is then re-sized under consideration of hybrid-electric propulsion technology. This is performed for parallel, serial, and fully-electric powertrain architectures. Finally, sensitivity studies are conducted to assess the validity of the basic assumptions and approaches regarding the design of hybrid-electric aircraft. Both methods are found to predict the maximum take-off mass (MTOM) of the reference aircraft with less than 4\% error. The MTOM and payload-range energy efficiency of various (hybrid-) electric configurations are predicted with a maximum difference of approximately 2\% and 5\%, respectively. The results of this study confirm a correct formulation and implementation of the two design methods, and the data obtained can be used by researchers to benchmark and validate their design tools.},
  language  = {en}
}
@inproceedings{FingerKhalsaKreyeretal.2019,
  author    = {Finger, Felix and Khalsa, R. and Kreyer, J{\"o}rg and Mayntz, Joscha and Braun, Carsten and Dahmann, Peter and Esch, Thomas and Kemper, Hans and Schmitz, O. and Bragard, Michael},
  title     = {An approach to propulsion system modelling for the conceptual design of hybrid-electric general aviation aircraft},
  series = {Deutscher Luft- und Raumfahrtkongress 2019, 30.9.-2.10.2019, Darmstadt},
  booktitle = {Deutscher Luft- und Raumfahrtkongress 2019, 30.9.-2.10.2019, Darmstadt},
  pages     = {15 Seiten},
  year      = {2019},
  abstract  = {In this paper, an approach to propulsion system modelling for hybrid-electric general aviation aircraft is presented. Because the focus is on general aviation aircraft, only combinations of electric motors and reciprocating combustion engines are explored. Gas turbine hybrids will not be considered. The level of the component's models is appropriate for the conceptual design stage. They are simple and adaptable, so that a wide range of designs with morphologically different propulsive system architectures can be quickly compared. Modelling strategies for both mass and efficiency of each part of the propulsion system (engine, motor, battery and propeller) will be presented.},
  language  = {en}
}
@inproceedings{LudowicyRingsFingeretal.2018,
  author    = {Ludowicy, Jonas and Rings, Ren{\´e} and Finger, Felix and Braun, Carsten},
  title     = {Sizing Studies of Light Aircraft with Serial Hybrid Propulsion Systems},
  series = {Luft- und Raumfahrt - Digitalisierung und Vernetzung : Deutscher Luft- und Raumfahrtkongress 2018. 4. - 6. September 2018 - Friedrichshafen},
  booktitle = {Luft- und Raumfahrt - Digitalisierung und Vernetzung : Deutscher Luft- und Raumfahrtkongress 2018. 4. - 6. September 2018 - Friedrichshafen},
  pages     = {11 S.},
  year      = {2018},
  language  = {en}
}
@inproceedings{FingerGoettenBraun2018,
  author    = {Finger, Felix and G{\"o}tten, Falk and Braun, Carsten},
  title     = {Initial Sizing for a Family of Hybrid-Electric VTOL General Aviation Aircraft},
  series = {67. Deutscher Luft- und Raumfahrtkongress 2018},
  booktitle = {67. Deutscher Luft- und Raumfahrtkongress 2018},
  pages     = {14 S.},
  year      = {2018},
  language  = {en}
}
@inproceedings{LudowicyRingsFingeretal.2018,
  author    = {Ludowicy, Jonas and Rings, Ren{\´e} and Finger, Felix and Braun, Carsten},
  title     = {Sizing Studies of Light Aircraft with Parallel Hybrid Propulsion Systems},
  series = {Deutscher Luft- und Raumfahrtkongress 2018},
  booktitle = {Deutscher Luft- und Raumfahrtkongress 2018},
  doi       = {10.25967/480227},
  pages     = {15 S.},
  year      = {2018},
  language  = {en}
}
@article{GoettenFingerHavermannetal.2018,
  author    = {G{\"o}tten, Falk and Finger, Felix and Havermann, Marc and Braun, Carsten and Gomez, Francisco and Bill, C.},
  title     = {On the flight performance impact of landing gear drag reduction methods for unmanned air vehicles},
  series = {Deutscher Luft- und Raumfahrtkongress 2018},
  journal   = {Deutscher Luft- und Raumfahrtkongress 2018},
  publisher = {DGLR},
  address   = {Bonn},
  doi       = {10.25967/480058},
  pages     = {11 S.},
  year      = {2018},
  abstract  = {The flight performance impact of three different landing gear configurations on a small, fixed-wing UAV is analyzed with a combination of RANS CFD calculations and an incremental flight performance algorithm. A standard fixed landing gear configuration is taken as a baseline, while the influence of retracting the landing gear or applying streamlined fairings is investigated. A retraction leads to a significant parasite drag reduction, while also fairings promise large savings. The increase in lift-to-drag ratio is reduced at high lift coefficients due to the influence of induced drag. All configurations are tested on three different design missions with an incremental flight performance algorithm. A trade-off study is performed using the retracted or faired landing gear's weight increase as a variable. The analysis reveals only small mission performance gains as the aerodynamic improvements are negated by weight penalties. A new workflow for decision-making is presented that allows to estimate if a change in landing gear configuration is beneficial for a small UAV.},
  language  = {en}
}
@inproceedings{FingerBraunBil2019,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Impact of Engine Failure Constraints on the Initial Sizing of Hybrid-Electric GA Aircraft},
  series = {AIAA Scitech 2019 Forum},
  booktitle = {AIAA Scitech 2019 Forum},
  doi       = {10.2514/6.2019-1812},
  year      = {2019},
  language  = {en}
}
@article{Finger2016,
  author    = {Finger, Felix},
  title     = {Senkrechtstarter: FH-Absolvent wird f{\"u}r Transportdrohne ausgezeichnet},
  series = {campushunter: das etwas andere Karrieremagazin - Wintersemester 16/17},
  journal   = {campushunter: das etwas andere Karrieremagazin - Wintersemester 16/17},
  number    = {17. Regionalausgabe Aachen},
  publisher = {Campushunter Media},
  address   = {Heidelberg},
  issn      = {2196-9426},
  pages     = {116 -- 117},
  year      = {2016},
  language  = {de}
}
@article{FingerBraunBil2018,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Impact of electric propulsion technology and mission requirements on the performance of VTOL UAVs},
  series = {CEAS Aeronautical Journal},
  volume    = {10},
  journal   = {CEAS Aeronautical Journal},
  number    = {3},
  publisher = {Springer},
  issn      = {1869-5582 print},
  doi       = {10.1007/s13272-018-0352-x},
  pages     = {843},
  year      = {2018},
  abstract  = {One of the engineering challenges in aviation is the design of transitioning vertical take-off and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the take-off and landing phases. This mass increase is typically higher for aircraft with a separate lift propulsion system than for aircraft that use the cruise propulsion system to support a dedicated lift system. However, for a cost-benefit trade study, it is necessary to quantify the impact the VTOL requirement and propulsion configuration has on aircraft mass and size. For this reason, sizing studies are conducted. This paper explores the impact of considering a supplemental electric propulsion system for achieving hovering flight. Key variables in this study, apart from the lift system configuration, are the rotor disk loading and hover flight time, as well as the electrical systems technology level for both batteries and motors. Payload and endurance are typically used as the measures of merit for unmanned aircraft that carry electro-optical sensors, and therefore the analysis focuses on these particular parameters.},
  language  = {en}
}
@article{Finger2017,
  author    = {Finger, Felix},
  title     = {Vergleichende Leistungs- und Nutzenbewertung von VTOL- und CTOL-UAVs},
  series = {Luft- und Raumfahrt : informieren, vernetzen, f{\"o}rdern / Hrsg.: Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt},
  volume    = {38},
  journal   = {Luft- und Raumfahrt : informieren, vernetzen, f{\"o}rdern / Hrsg.: Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt},
  number    = {1},
  issn      = {0173-6264},
  pages     = {44 -- 47},
  year      = {2017},
  language  = {de}
}
@inproceedings{Finger2016,
  author    = {Finger, Felix},
  title     = {Comparative Performance and Benefit Assessment of VTOL and CTOL UAVs},
  series = {Deutscher Luft- und Raumfahrtkongress (DLRK) 2016, 13.-15.9.2016},
  booktitle = {Deutscher Luft- und Raumfahrtkongress (DLRK) 2016, 13.-15.9.2016},
  pages     = {10 Seiten},
  year      = {2016},
  language  = {en}
}
@inproceedings{FingerBraunBil2017,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {The Impact of Electric Propulsion on the Performance of VTOL UAVs},
  series = {Deutscher Luft- und Raumfahrtkongress 2017, DLRK , M{\"u}nchen},
  booktitle = {Deutscher Luft- und Raumfahrtkongress 2017, DLRK , M{\"u}nchen},
  year      = {2017},
  language  = {en}
}
@inproceedings{FingerBraunBil2017,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {A Review of Configuration Design for Distributed Propulsion Transitioning VTOL Aircraft},
  series = {Asia-Pacific International Symposium on Aerospace Technology 2017, APISAT 2017, Seoul, Korea},
  booktitle = {Asia-Pacific International Symposium on Aerospace Technology 2017, APISAT 2017, Seoul, Korea},
  pages     = {15 Seiten},
  year      = {2017},
  language  = {en}
}
@inproceedings{FingerBraunBil2018,
  author    = {Finger, Felix and Braun, Carsten and Bil, Cees},
  title     = {Case studies in initial sizing for hybrid-electric general aviation aircraft},
  series = {2018 AIAA/IEEE Electric Aircraft Technologies Symposium, Cincinnati, Ohio},
  booktitle = {2018 AIAA/IEEE Electric Aircraft Technologies Symposium, Cincinnati, Ohio},
  doi       = {10.2514/6.2018-5005},
  year      = {2018},
  language  = {en}
}
@article{FingerGoetten2019,
  author    = {Finger, Felix and G{\"o}tten, Falk},
  title     = {Neue Ans{\"a}tze f{\"u}r die Entwicklung von unbemannten Flugger{\"a}ten},
  series = {Ingenieurspiegel},
  volume    = {2019},
  journal   = {Ingenieurspiegel},
  number    = {1},
  isbn      = {1868-5919},
  pages     = {67 -- 68},
  year      = {2019},
  abstract  = {Wie sieht das unbemannte Flugzeug von {\"U}bermorgen aus? Dieser Frage stellen sich Forscher an der Fachhochschule Aachen. Die weltweit rasant fortschreitende Entwicklung des Marktes f{\"u}r unbemannte Flugger{\"a}te (UAVs - „Unmanned Aerial Vehicles") bietet großes Potenzial f{\"u}r Wachstum und Wertsch{\"o}pfung. Unbemannte fliegende Systeme k{\"o}nnen - f{\"u}r bestimmte Anwendungsgebiete - wesentlich g{\"u}nstiger, kleiner und effizienter ausgelegt werden als bemannte L{\"o}sungen. Dabei sind sich viele Unternehmen {\"u}ber das m{\"o}gliche Potential dieser Technologie noch gar nicht bewusst.},
  language  = {de}
}
@article{GoettenFinger2020,
  author    = {G{\"o}tten, Falk and Finger, Felix},
  title     = {PhoenAIX - Die modulare Transportdrohne},
  series = {Ingenieurspiegel},
  volume    = {2020},
  journal   = {Ingenieurspiegel},
  number    = {1},
  publisher = {Public Verlag},
  address   = {Bingen},
  isbn      = {1868-5919},
  pages     = {38 -- 40},
  year      = {2020},
  abstract  = {Die autonome, unbemannte Luftfahrt ist einer der Schl{\"u}sselsektoren f{\"u}r die Zukunft der Luftfahrt. In diesem rasant wachsenden Bereich nehmen senkrecht startende und senkrecht landende Flugzeuge (Vertical Take-Off and Landing - VTOL) einen besonderen Platz ein. Ein VTOL-Flugzeug (manchmal auch „Transitionsflugger{\"a}t" genannt) verbindet die Eigenschaft des Helikopters, {\"u}berall starten und landen zu k{\"o}nnen, mit den Geschwindigkeits-, Reichweiten und Flugdauervorteilen des Starrfl{\"u}glers. Grunds{\"a}tzlich wird die Senkrechtstart- und -landef{\"a}higkeit sowohl von zivilen als auch von milit{\"a}rischen Betreibern unbemannter Flugger{\"a}te (UAVs) gew{\"u}nscht. Trotzdem bietet der Markt nur eine geringe Anzahl von VTOL-UAVs, da qualitativ hochwertige Entw{\"u}rfe eine ausgesprochene Herausforderung in der Entwicklung darstellen. An der FH Aachen wird deshalb seit {\"u}ber 5 Jahren an der Auslegung und Analyse von solchen unbemannten VTOL Flugzeugen geforscht. Das neuste Projekt ist der Eigenentwurf einer großen, senkrechtstartenden Transportdrohne. Das „PhoenAIX" getaufte Flugger{\"a}t wird von Falk G{\"o}tten und Felix Finger im Rahmen einer EFRE-F{\"o}rderung entwickelt.},
  language  = {de}
}