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Item type:Publication, Access status: without files , Conceptual design and energy management analysis of turbofan-based hybrid-electric propulsion(American Institute of Aeronautics and Astronautics (AIAA), 2025-08-18); ; ; Hybrid-electric propulsion systems offer the potential to make aircraft more efficient by using electric energy to cover a share of the total energy demand. However, resolving questions related to aircraft hybridization, namely the potential fuel consumption benefits and the energy management throughout the mission, is vital. This highlights the importance of holistic evaluation methods. Hence, this paper introduces a method for the design and evaluation of hybrid-electric propulsion systems. The method enhances current sizing methods by modeling a hybrid-electric turbofan and estimating electrical losses for the electric power train to explore hybrid energy management strategies. The method is demonstrated using the short–medium-range concept aircraft D239. Initial simulations indicate a total increase in the block fuel mass of approximately 2.7% with constant hybridization throughout the 800 n mile reference mission. However, optimizing the energy management strategy reveals an improved result of a 1.6% increase in mission block fuel. Key factors contributing to this improvement include using hybrid-electric power exclusively during the climb phase, shorter mission ranges, and omitting battery charging during flight. However, an overall increase in the block fuel mass persists under realistic assumptions. This highlights the need for further exploration of hybrid-electric concepts and methodical refinement.Publicationtype: Journal Article25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Aircraft load estimation using linear parameter-varying system-based hybrid observers(American Institute of Aeronautics and Astronautics (AIAA), 2025-05-01); The hybrid loads observer has demonstrated its precision in estimating structural loads and wind disturbances in prior applications. This level of precision is attained by combining a high-fidelity physical, nonlinear flight dynamics model with a data-driven correction model. To mitigate the typically high computational effort, the nonlinear model is substituted in this work with a linear parameter-varying (LPV) system. Therefore, the nonlinear model is approximated by scheduled Linear Time-Invariant models derived from Jacobian linearization. The robustness of this novel approach against parameter uncertainties is evaluated through simulated flight test studies using a subscale test aircraft as an example. It is demonstrated that increased model uncertainties lead to wind estimation accuracy reduction. Additionally, increased parameter uncertainties adversely affect the accuracy of structural load estimation within the model-based (physical) part of the observer. Nonetheless, this loss of accuracy can be compensated by the correction model, leading to the typical high load estimation accuracy of the hybrid loads observer. Finally, experimental data from wind-tunnel tests, utilizing a 1-degree-of-freedom representative test wing, confirms the high estimation accuracy of the LPV-based hybrid loads observer. Despite employing low-fidelity models, achieving high accuracy is feasible while maintaining the characteristic low complexity of the correction model.Publicationtype: Journal Article43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Modeling, design, and flight testing of three flutter controllers for a flying-wing droneThree flutter-suppression designs for a flexible flying-wing research drone are discussed, along with the modeling and flight-test results. The drone, with wing span of 10 feet, aspect ratio of almost 9, and control surfaces along the entire wing trailing edges, was developed for flight research into the modeling and control of highly elastic aircraft. The lowspeed vehicle was designed to exhibit body-freedom flutter in its flight envelope. The all-important dynamic modeling of the vehicle, used for analysis and control design, is based on a mean-axis formulation and quasi-steady aerodynamics, with the nondimensional aerodynamic/aeroelastic coefficients updated from flight tests. Flutter-modeling results were found to agree with those from NASTRAN and flight tests. The three different flutter-suppression approaches include both fairly classical and multivariable methods, all fixed gains but with different architectures. The primary controldesign objective was to augment the damping of the eventual flutter mode at a design condition below the open-loop flutter speed, for safety of flight, and to achieve a closed-loop flutter speed at least as high as the open-loop flutter speed. Analysis and flight tests revealed that all three designs achieved these design goals. In addition, two of these designs actually expanded the flutter boundary. The theoretical stability robustness of all three controllers at the design flight condition is quite good, but there are differences in controller complexity. Research is currently underway to further expand the flutter boundary using all three design approaches.Publicationtype: Journal Article233 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Cloud encounter impact on operational and economical effectiveness of hybrid-laminar-flow-control aircraftHowever, due to high sensitivities of HLFC toward operational boundary conditions, estimations of its overall benefit are usually afflicted with large uncertainties. Among the critical environmental factors is the degradation of laminarity when flying through clouds at high altitudes. This paper provides an assessment on operational and economical effectiveness of HLFC aircraft with a detailed inclusion of the cloud encounter effect in three steps. First the expected time in cloud (TIC) in a real route network with cloud data given by the European Centre for Medium-Range Weather Forecast is analyzed, yielding an average TIC of 10%. Subsequently, HLFC fuel efficiency with and without considering the cloud effect on mid- to long-range aircraft is dealt with. Results show an average drop of fuel benefit from 12.8 to 12.0% due to clouds. The effectiveness of lateral route optimization to reduce the impact of clouds is investigated in the last analysis. Outcomes show that these mitigation strategies are economically beneficial for few cases only. The overall picture confirms that cloud encounter must not be neglected when assessing aircraft with HLFC.Publicationtype: Journal Article266 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Approach to forecast air-traffic movements at capacity-constrained airports(American Institute of Aeronautics and Astronautics (AIAA), 2015-03-25); ; ; A model chain being implemented in one tool has been presented to derive a flight plan based on the capacities of the airport and given passenger demand, and applied on Hamburg Airport. Validation shows that, even though every submodel uses certain assumptions and simplifications, the tool chain generates generic flight plans that highly match current sample flight plans. Thus, the tool offers airports the opportunity to easily evaluate existing infrastructure capacity and planned infrastructure extensions regarding future air-traffic movements. Using a modular tool chain analyzing drivers for air-traffic growth, considering airline and passenger preferences, fleet development, and airport capacity, the air-traffic movements are forecasted. By validation of each submodel, a high-quality forecast is achieved. Because of the modularity of the tool chain, every submodel can easily be changed or adapted to prospective developments.Publicationtype: Journal Article47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Feasibility study of a hybrid ice protection systemAkey design factor impacting the use of electrical power to drive aircraft systems and subsystems is energy efficiency. With the design of an all-electric, hybrid ice protection system, energy consumption can be reduced to a large extent. The hybridization is achieved through an intentional partitioning of the ice at the stagnation line by melting via surface heating and ice shedding in the unheated regions of the airfoil surface via an electromechanical deicing systembased on piezoelectric multilayer actuators. To further reduce energy consumption, the adhesion forces between the ice and the airfoil surface can be reduced using an ultrasmooth,nanostructured surfacewithwater-and ice-repellent properties that encourages ice shedding. Experimental investigations, performed in a laboratory-scale icing wind tunnel for a smallscale configuration, reveal that the hybrid approach for ice protection reliably sheds the ice accreted on the airfoil surface.Comparedwith an all-thermoelectric systemfor ice protection investigated in the same icingwind tunnel facility using identical test conditions, the hybrid approachwas demonstrated to reduce power consumption up to 91%. Beyond the laboratory tests, numerical simulations of the hybrid strategy analogous to the one used for the experiments are performed. The time history of the residual ice shapes aft of the heated region is simulated using the ice accretion prediction software LEWICE2D for a wet-running anti-icing subsystem. Finite element analyses of the effects of the piezoelectric actuators are then performed using Abaqus to investigate the ice-shedding capability in the unheated regions of the airfoil surface. The numerical results show that the variation in the different ice shapes affects the stiffness of themodel. It becomes obvious that the critical threshold for ice shedding, that is, the stiffness that determineswhether residual ice delaminates fromthe airfoil surface, is affected to aminor extent by the interfacial area and predominantly by the thickness of the ice layer. Further, the simulation results correlate well with experimental results obtained in the icing wind tunnel. It can be concluded that reliable operation of the hybrid system for ice shedding can be guaranteed when using a harmonic sweep excitation able to excite the structure at its resonance.Publicationtype: Conference Paper91