The Strategic Research and Innovation Agenda and NASA N+3 goals have set new challenges for the aeronautical community via declaration of dramatic efficiency improvements. Because further evolutionary improvements do not appear to be sufficient, envisioning disruptive technologies turn out to be essential to reach the set of future targets. The design of innovative integrated energy–power systems is certainly a major promising element as can be shown by the increasing interest toward hybrid energy and universally electric aircraft. The consideration of these new types of aircraft represents a new challenge for conventional aircraft sizing and performance methods. As an extension of the conventional methods used for fuel-energy aircraft, a sizing and performance methodology for hybrid-energy aircraft is proposed. A design study of a battery and fuel hybrid-energy single-aisle retrofit is conducted to demonstrate the methodology and to analyze the implications of the associated new design variables on the s...

Ram air–based thermal management systems (TMS) are investigated herein for the cooling of future hybrid-electric aircraft. The developed TMS model consists of all components required to estimate the impacts of mass, drag, and fuel burn on the aircraft, including heat exchangers, coldplates, ducts, pumps, and fans. To gain a better understanding of the TMS, one- and multi-dimensional system sensitivity analyses were conducted. The observations were used to aid with the numerical optimization of a ram air–based TMS towards the minimum fuel burn of a 180-passenger short-range partial-turboelectric aircraft with a power split of up to 30% electric power. The TMS was designed for the conditions at the top of the climb. For an aircraft with the maximum power split, the additional fuel burn caused by the TMS is 0.19%. Conditions occurring at a hot-day takeoff represent the most challenging off-design conditions for TMS. Steady-state cooling of all electric components with the designed TMS is possible during a hot-day takeoff if a small puller fan is utilized. Omitting the puller fan and instead oversizing the TMS is an alternative, but the fuel burn increase on aircraft level grows to 0.29%.

Noise and greenhouse gas emission targets set by e.g., the EU commission, NASA, and ICAO oblige the aviation industry to reduce its environmental footprint. Battery-powered hybrid-electric aircraft are currently being investigated in this regard as they can potentially reduce in-flight greenhouse gas emissions and noise. However, most studies to date have focused on the CO₂ emission reduction potential instead of considering the total life cycle environmental impact. Hence, within this study an environmental life cycle assessment method for a hybrid-electric aircraft is developed and applied, supplemented by a direct operating costs analysis. This allows the simultaneous evaluation of the environmental impact reduction potential and the economic consequences for aircraft operators. This demonstrates the faced trade-off and contributes to a meaningful review process. A single-aisle transport aircraft (A320 class) serves as a use case for the established methodology. It consists of the conceptual aircraft design, the environmental life cycle assessment, and the direct operating costs analysis for a conventional reference aircraft and a hybrid-electric aircraft with a discrete parallel powertrain architecture. It should be noticed that the focus of this study is the comparison of conceptual aircraft designs of the same fidelity on system level, in lieu of the detailed modeling of a hybrid-electric aircraft. Results show that for a degree of hybridization of 0.3, the environmental impact of the hybrid-electric configuration increased by $$15.1\%$$15.1 % , while the operating costs increased by $$41.0\%$$41.0 % compared to a conventional reference aircraft. For a future scenario, favourable for hybrid-electric aircraft with i.a. renewable electricity production, the environmental impact could be reduced by $$7.0\%$$7.0 % compared to the reference aircraft. At the same time, the operating costs gap between both configurations decreases to $$+ 26.8\%$$+ 26.8 % . Hybrid-electric aircraft should therefore be investigated further as a potential solution to reduce the environmental impact of aviation, if simultaneously to developing them the expansion of renewable energies is fostered. Nevertheless, this reduction in environmental impact involves a high direct operating costs penalty.

Urban air mobility (UAM) is the idea of creating a future mobility market through the introduction of a new mode of aerial transport with substantial travel time advantages. A key factor diminishing travel time savings is vertiport processes. So far, vertiport throughput capacity has only been studied in a static manner using analytical methods, which has been found to be insufficient. This paper wants to increase the level of understanding of operational dynamics on vertiport airfields by being the first to apply agent-based simulation. For this purpose, an existing vertiport model consisting of pads, gates and stands was refined through two means. First, a sensitivity study with over 100 simulations was executed shedding light on the driving processes on a vertiport airfield. Second, an expert interview series with 17 participants was conducted, letting the experts evaluate the model and specify relevant parameter values. Three main results should find mention here: (1) Pad operations were identified to be most impactful on passenger delays. (2) Pad and gate processes have a threshold capacity beyond which delays increase exponentially. (3) A refined vertiport model is presented, including the 27 most relevant parameters and their value specification. In conclusion, this paper finds that optimized vertiport airfield design is crucial to UAM operations, and dynamic passenger and vehicle interactions cannot be neglected.

Providing sufficient cooling power for an aircraft will become increasingly challenging with the introduction of (hybrid-) electric propulsion. To avoid excessive drag from heat exchangers, the heat sink potential of the aircraft surface is evaluated in this study. Semi-empirical correlations are used to estimate aircraft surface area and heat transfer. The impact of surface heating on aircraft drag is qualitatively assessed. Locating surface heat exchangers where fully turbulent flow is present promises a decrease in aircraft drag. Surface cooling potential is investigated over a range from small regional aircraft to large wide body jets and a range of surface temperatures. Four mission points are considered: Take-off, hot day take-off, climb and cruise. The results show that surface heat exchangers can provide cooling power in the same order of magnitude as the waste heat expected from (hybrid-) electric drive trains for all sizes of considered aircraft. Also, a clear trend favouring smaller aircraft with regards to the ratio of available to required cooling power is visible.