One major focus of enhancing the fuel efficiency in aviation lies in implementing drag reduction technologies. There exists a significant potential to reduce the viscous drag to facilitate this objective by delaying the laminar to turbulent transition of boundary layers using hybrid laminar flow control. This study evaluates the potential of novel Monte Carlo Bayesian optimization techniques used in conjunction with trust regions for high-dimensional aerodynamic design of transonic laminar airfoils and wings using black-box transition models that lack gradient information. The aerodynamic analysis considered in this study is based on coupled Euler-boundary layer equations with a mid-fidelity conical 2.75D approach, which is more suited for the objective to balance the reduction of viscous and wave drag, in comparison to the conventional low-fidelity panel methods used for fully turbulent designs. A comparative analysis of the underlying acquisition functions governing the Bayesian decision policy is also presented in this work. The Bayesian design framework adapted in this study delivers a 98-dimensional laminar wing with very high aerodynamic efficiency and robust performance within a wide design range. Laminar extensions close to 50
Handling qualities (HQ) evaluations represent a fundamental aspect of the rotorcraft development cycle, ensuring that aircraft meet the necessary standards for pilot control and mission performance. These assessments are traditionally carried out through the execution of Mission Task Elements (MTEs) and the use of subjective pilot evaluations, most commonly utilizing the Cooper-Harper rating scale. Although computer-based simulations have continued to advance in fidelity and utility, real-time pilot feedback during live flight testing remains a critical element in assigning accurate and reliable HQ ratings. However, as rotorcraft systems evolve and incorporate increasing levels of autonomy, the extent of direct pilot involvement is being significantly reduced. Consequently, objective measures of performance are becoming more central to the evaluation process. This evolving landscape underscores the need for innovative metrics and analytical techniques capable of supporting HQ evaluations across a wide range of automation levels. In response, this paper introduces a novel methodology specifically designed to assist in the HQ assessment of vertical takeoff and landing (VTOL) aircraft, regardless of their level of pilot interaction or autonomy. The proposed approach leverages rainflow counting algorithms to evaluate vehicle dynamics during MTEs. One of the primary advantages of this method is its ability to provide rapid, meaningful insights into aircraft performance that are not confined to traditional time- or frequency-domain frameworks. Additionally, it allows performance data to be directly connected to task-specific requirements, while showing a high degree of correlation with pilot commentary and Cooper-Harper handling quality ratings.
In this paper, we present a thermodynamic cycle-based analysis of the effect of aircraft engine design and fuel selection on contrail formation, which is evaluated using the Schmidt–Appleman criterion (SAC). Our goal is to examine the possibilities and limits of contrail avoidance to reduce the climate impact of aviation. We use the gas turbine performance software GasTurb to study geared-turbofan and open-rotor engine designs for contemporary short- to medium-range aircraft. The design parameters are overall pressure ratio, burner exit temperature, and, for the geared-turbofan, the design bypass ratio. We vary these parameters in wide ranges to cover all technically feasible engine designs. We find that contrail formation at current cruise altitudes cannot be avoided with the examined contemporary and future engine cycles. In the best case, the contrail formation altitude is increased by just over 230 m. This comes with a significant engine efficiency penalty. In contrast, future, more efficient engine cycles will decrease the contrail formation altitude, leading to the formation of more contrails. When using hydrogen as fuel instead of kerosene, contrails form at approximately 1.6 km lower altitudes according to the Schmidt–Appleman criterion. We thus find that it is practically impossible to avoid contrail formation, as predicted by the SAC, using the engine cycles and fuels examined in this paper. Operational contrail avoidance measures like cruise altitude adjustment or flying around ice-supersaturated atmospheric layers present themselves as more practicable.
In this paper, a methodology for the conceptual sizing of firefighting aircraft mission systems is proposed. This work focuses on firefighting mission systems for aircraft in the “water scooper” category, specifically designed to collect water directly from natural sources. This capability enables rapid tank refilling and enhances operational efficiency by eliminating the need to return to base between water drops. The methodology relies on the geometric scaling of the Canadair CL-415 mission system, adopted as the reference. The analysis of its components and the governing equations of the method are presented in detail. The proposed methodology can perform the preliminary sizing of the mission system at the component level, evaluating weight, volume, power consumption, and operational performance. Starting from the reference architecture, it can adapt the mission system to different aircraft geometries, within a range of sizes around the reference, and to variations in its component configuration. It is therefore suited both to the conversion of existing airframes and to new aircraft concepts sharing this architecture. As a case study, the methodology is applied to the seaplane concept proposed within the COLOSSUS European research project, and the results are discussed to assess the effectiveness of the model.
Technological advancements alongside with the autonomy of systems have fostered the introduction of new aerial concepts such as Urban Air Mobility (UAM). Towards integrating these operations in urban environments, besides technological aspects, factors including societal acceptance, play a fundamental role in the success of UAM. Safe simulation environments provided by immersive technologies such as Virtual Reality can enhance the assessment of social acceptance studies. This study examines of how mission transparency affects public acceptance of drones in urban environments using Virtual Reality. A within-subjects design, with a four-level factor variation for mission transparency was conducted, with the conditions: baseline, lighting information, color-coding and billboard signage. A total of 98 subjects experienced the conditions and provided subjective ratings regarding their perceptions. Results from a repeated measures ANOVA indicate that there is a significant difference across the conditions (p- value<0.001 ), with the billboard experimental condition presenting highest risk perception. Influence of participants characteristics such as preexisting opinion on drones and subscription to delivery services were found to affect participants ratings. Different than previous works, this study contributes by extending the knowledge on drone acceptance as well as providing a streamlined workflow for creating high-fidelity VR applications to Urban Air Mobility.
