@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} } @misc{HilleStumpfMayntzetal.2023, author = {Hille, Sebastian and Stumpf, Eike and Mayntz, Joscha and Dahmann, Peter}, title = {Prediction of sound exposure caused by a landing motor glider with recuperating propellers}, series = {AIAA SCITECH 2023 Forum}, journal = {AIAA SCITECH 2023 Forum}, publisher = {AIAA}, address = {Reston, Va.}, doi = {10.2514/6.2023-0211}, year = {2023}, abstract = {This paper presents an approach to predicting the sound exposure on the ground caused by a landing aircraft with recuperating propellers. The noise source along the trajectory of a flight specified for a steeper approach is simulated based on measurements of sound power levels and additional parameters of a single propeller placed in a wind tunnel. To validate the measured data/measurement results, these simulations are also supported by overflight measurements of a test aircraft. It is shown that the simple source models of propellers do not provide fully satisfactory results since the sound levels are estimated too low. Nevertheless, with a further reference comparison, margins for an acceptable increase in the sound power level of the aircraft on its now steeper approach path could be estimated. Thus, in this case, a +7 dB increase in SWL would not increase the SEL compared to the conventional approach within only 2 km ahead of the airfield.}, language = {en} } @article{HammerQuitterMayntzetal.2023, author = {Hammer, Thorben and Quitter, Julius and Mayntz, Joscha and Bauschat, J.-Michael and Dahmann, Peter and G{\"o}tten, Falk and Hille, Sebastian and Stumpf, Eike}, title = {Free fall drag estimation of small-scale multirotor unmanned aircraft systems using computational fluid dynamics and wind tunnel experiments}, series = {CEAS Aeronautical Journal}, journal = {CEAS Aeronautical Journal}, publisher = {Springer}, address = {Wien}, issn = {1869-5590 (Online)}, doi = {10.1007/s13272-023-00702-w}, pages = {14 Seiten}, year = {2023}, abstract = {New European Union (EU) regulations for UAS operations require an operational risk analysis, which includes an estimation of the potential danger of the UAS crashing. A key parameter for the potential ground risk is the kinetic impact energy of the UAS. The kinetic energy depends on the impact velocity of the UAS and, therefore, on the aerodynamic drag and the weight during free fall. Hence, estimating the impact energy of a UAS requires an accurate drag estimation of the UAS in that state. The paper at hand presents the aerodynamic drag estimation of small-scale multirotor UAS. Multirotor UAS of various sizes and configurations were analysed with a fully unsteady Reynolds-averaged Navier-Stokes approach. These simulations included different velocities and various fuselage pitch angles of the UAS. The results were compared against force measurements performed in a subsonic wind tunnel and provided good consistency. Furthermore, the influence of the UAS`s fuselage pitch angle as well as the influence of fixed and free spinning propellers on the aerodynamic drag was analysed. Free spinning propellers may increase the drag by up to 110\%, depending on the fuselage pitch angle. Increasing the fuselage pitch angle of the UAS lowers the drag by 40\% up to 85\%, depending on the UAS. The data presented in this paper allow for increased accuracy of ground risk assessments.}, language = {en} } @inproceedings{MayntzKeimerDahmannetal.2022, author = {Mayntz, Joscha and Keimer, Jona and Dahmann, Peter and Hille, Sebastian and Stumpf, Eike and Fisher, Alex and Dorrington, Graham}, title = {Electrical Drive and Regeneration in General Aviation Flight with Propellers}, series = {Deutscher Luft- und Raumfahrtkongress 2020}, booktitle = {Deutscher Luft- und Raumfahrtkongress 2020}, publisher = {DGLR}, address = {Bonn}, doi = {10.25967/530100}, pages = {8 Seiten}, year = {2022}, abstract = {Electric flight has the potential for a more sustainable and energy-saving way of aviation compared to fossil fuel aviation. The electric motor can be used as a generator inflight to regenerate energy during descent. Three different approaches to regenerating with electric propeller powertrains are proposed in this paper. The powertrain is to be set up in a wind tunnel to determine the propeller efficiency in both working modes as well as the noise emissions. Furthermore, the planned flight tests are discussed. In preparation for these tests, a yaw stability analysis is performed with the result that the aeroplane is controllable during flight and in the most critical failure case. The paper shows the potential for inflight regeneration and addresses the research gaps in the dual role of electric powertrains for propulsion and regeneration of general aviation aircraft.}, language = {en} } @misc{KeimerGirbigMayntzetal.2022, author = {Keimer, Jona and Girbig, Leo and Mayntz, Joscha and Tegtmeyer, Philipp and Wendland, Frederik and Dahman, Peter and Fisher, Alex and Dorrington, Graham}, title = {Flight mission optimization for eco-efficiency in consideration of electric regeneration and atmospheric conditions}, series = {AIAA AVIATION 2022 Forum}, journal = {AIAA AVIATION 2022 Forum}, publisher = {AIAA}, address = {Reston, Va.}, doi = {10.2514/6.2022-4118}, year = {2022}, abstract = {The development and operation of hybrid or purely electrically powered aircraft in regional air mobility is a significant challenge for the entire aviation sector. This technology is expected to lead to substantial advances in flight performance, energy efficiency, reliability, safety, noise reduction, and exhaust emissions. Nevertheless, any consumed energy results in heat or carbon dioxide emissions and limited electric energy storage capabilities suppress commercial use. Therefore, the significant challenges to achieving eco-efficient aviation are increased aircraft efficiency, the development of new energy storage technologies, and the optimization of flight operations. Two major approaches for higher eco-efficiency are identified: The first one, is to take horizontal and vertical atmospheric motion phenomena into account. Where, in particular, atmospheric waves hold exciting potential. The second one is the use of the regeneration ability of electric aircraft. The fusion of both strategies is expected to improve efficiency. The objective is to reduce energy consumption during flight while not neglecting commercial usability and convenient flight characteristics. Therefore, an optimized control problem based on a general aviation class aircraft has to be developed and validated by flight experiments. The formulated approach enables a development of detailed knowledge of the potential and limitations of optimizing flight missions, considering the capability of regeneration and atmospheric influences to increase efficiency and range.}, language = {en} } @misc{MayntzKeimerTegtmeyeretal.2021, author = {Mayntz, Joscha and Keimer, Jona and Tegtmeyer, Philipp and Dahmann, Peter and Hille, Sebastian and Stumpf, Eike and Fisher, Alex and Dorrington, Graham}, title = {Aerodynamic Investigation on Efficient Inflight Transition of a Propeller from Propulsion to Regeneration Mode}, series = {AIAA SCITECH 2022 Forum}, journal = {AIAA SCITECH 2022 Forum}, publisher = {AIAA}, address = {Reston, Va.}, doi = {10.2514/6.2022-0546}, year = {2021}, abstract = {This paper discusses a new way of inflight power regeneration for electric or hybrid-electric driven general aviation aircraft with one powertrain for both configurations. Three different approaches for the shift from propulsion to regeneration mode are analyzed. Numerical cal-culation and wind tunnel results are compared and show the highest regeneration potential for the "Windmill" approach, where the propeller blades are flipped, and rotation is reversed. A combination of all regeneration approaches for a realistic flight mission is discussed.}, language = {en} }