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The winter storm of late 2022 caused difficulties for many US-based airlines, but none more so than Southwest Airlines. Like other airlines, Southwest canceled flights in the early stages of the storm. Their attempted recoveries failed due to procedural and technology issues. The airline was unable to cope with the magnitude of canceled flights, aircraft and crews in the wrong places, disrupted passenger plans, and luggage separated from its owners. Over the next several days, Southwest canceled tens of thousands of flights, called in thousands of additional staff to support manual operations, and flew a reduced schedule for a time before returning to normal operations. The case provides numerous scenarios for you to analyze and research, to strengthen your understanding of the underlying concepts. [ABSTRACT FROM AUTHOR]

The behaviour of a structural component, such as the spreader installed on an aeroplane passenger seat made of the magnesium alloy Elektron® 43, is evaluated under a variety of load conditions. The purpose of this research project is to considerably reduce weight by employing the new alloy while keeping the strength and ductility necessary to meet the dynamic standards for both the 16 g forward and 14 g downward tests. A comprehensive campaign of static and dynamic testing on coupons was conducted to characterise the mechanical behaviour of the E43 magnesium alloy, from quasi-static to dynamic loading, and across a wide range of deformation rates. The elastic–plastic and strain rate sensitive material model of E43 is then calibrated using an FEA approach and LS-DYNA software, utilising stress–strain curves and properties determined from standardised experimental tensile and compression trials at varied strain rates. Finally, this material model was used to perform a finite element structural study of a major component of an aeroplane seat built using Elektron® 43 under typical in-flight stresses. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to: 1) Explore the mobility experiences of seniors with slow walking speeds (SSWS) in urban neighborhoods; and 2) Investigate their environmental barriers and supports. Methods: Go-along interviews were conducted with 36 SSWS residing in urban neighborhoods of Chongqing City, China. The mobility patterns and built environment factors influencing their mobility were revealed through cartographic analysis and thematic analysis. Results: SSWS primarily focused their activities within a 400-meter radius of their homes. Built environment themes included topography, neighborhood services, sidewalks, seating, traffic safety, weather, greenery, and lighting. Significant mobility barriers included long stairs, steep slopes, fast-moving objects on sidewalks, road crossings, and fast traffic. Available handrails, nearby food-service places, ample seating, and greenery were identified as supportive factors for their mobility. Conclusion: This study stands out as the first to specifically examine the mobility of SSWS within the built environment. We suggest that SSWS should be taken into account when establishing a benchmark for general design frameworks. These improvements not only contribute to the mobility of slow walkers but also have positive impacts on the broader population. [ABSTRACT FROM AUTHOR]

This study aims to compare the restraint performance of two child restraint systems (CRSs) used on airplanes—a rear-facing child seat (RFCS) and the child aviation restraint system (CARES)—for 1.5-year-old children, along with their compatibility with different types of aircraft seats. 16 g longitudinal dynamic tests were conducted on two types of aircraft seats with CRSs. Results indicate poor compatibility of CARES with Type A seats, significantly increasing the risk of head, neck, and abdominal injuries, with Nij exceeding the acceptable limit. In contrast, CARES exhibited good compatibility with Type B seats and effectively protected children. RFCS tests demonstrated effective injury risk reduction on both types of seats. It can be found that the performance of CARES depends on restraint status and seat dimensions; RFCSs provide adequate protection for 1.5-year-olds. Optimal protection can be achieved with smaller restrain angles of CRS and using thinner seat cushions. Compared to CARES, RFCSs better adapt to various aircraft seat structures, offering superior child protection. [ABSTRACT FROM AUTHOR]

Purpose: The lightweight design of aircraft seats can significantly improve fuel efficiency and reduce greenhouse gas emissions. Metal additive manufacturing (MAM) can produce lightweight topology-optimized designs with improved performance, but limited build volume restricts the printing of large components. The purpose of this paper is to design a lightweight aircraft seat leg structure using topology optimization (TO) and MAM with build volume restrictions, while satisfying structural airworthiness certification requirements. Design/methodology/approach: TO was used to determine a lightweight conceptual design for the seat leg structure. The conceptual design was decomposed to meet the machine build volume, a detailed CAD assembly was designed and print orientation was selected for each component. Static and dynamic verification was performed, the design was updated to meet the structural requirements and a prototype was manufactured. Findings: The final topology-optimized seat leg structure was decomposed into three parts, yielding a 57% reduction in the number of parts compared to a reference design. In addition, the design achieved an 8.5% mass reduction while satisfying structural requirements for airworthiness certification. Originality/value: To the best of the authors' knowledge, this study is the first paper to design an aircraft seat leg structure manufactured with MAM using a rigorous TO approach. The resultant design reduces mass and part count compared to a reference design and is verified with respect to real-world aircraft certification requirements. [ABSTRACT FROM AUTHOR]

Aircraft seats play a key role in the competition between aircraft companies seeking to differentiate themselves in terms of passengers' inflight experience. The seat design process relies on computational and experimental methods based on subjective measures, such as comfort rating questionnaires, and objective comfort indicators of seat-occupant interaction, such as contact pressure distribution and muscle activation. Previous studies around muscle activity for seating comfort assessment have primarily focused on more active scenarios or active systems. As such, there are limited studies about the role of muscle force in normal and relaxed sitting conditions, common in aircraft settings. This paper explores the relationship between activities of the neck muscles, sternocleidomastoid, and upper trapezius, measured from human participants seated sedentarily on conventional business aircraft seats and their perceived comfort with different backrest inclinations. The results show, for normal seating without neck pillow, no significant association is found between the backrest inclination and the neck's comfort or muscle activation. For general seating across different backrest inclinations, a positive medium correlation between muscle activation and comfort is found in upper trapezius (R = 0.5332, p = 0.0187). This work serves as a pilot study of this new approach of comfort evaluation using muscle feedback in seat designing processes and highlights the posterior's effect to seating experience in the neck region. [ABSTRACT FROM AUTHOR]

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Purpose: The goal of this work is to propose a local Active Noise Control system for an aircraft seat's headrest. This system should be able to extend the quiet zone beyond the physical microphones that can be placed behind the passenger's head due to space constraints. Furthermore, the control algorithm should perform efficiently when non-linear phenomena exist during the sound propagation. Methods: A functional link neural network and a computationally efficient Multiple Input Multiple Output approach are used for the system's implementation. The quiet zone is extended by linearly estimating the acoustic pressure in front of the headrest surface. The main novelty of this paper is the combination of these methods in an attempt to improve acoustic pressure attenuation performance, while keeping computational complexity low. Results: The proposed control algorithm has been evaluated through numerical simulations, including Finite Element Method and experimental tests at an aircraft cabin mock-up. The results show that for a real-world acoustic disturbance, a 10 dB reduction in sound pressure level was achieved 10 cm away from the headrest surface. In addition, the attenuation of some harmonics can reach 20 dB and in most cases is bigger than the linear FxLMS algorithm. Conclusions: To summarize, it has been demonstrated that a multichannel functional link neural network using a simple virtual sensing technique can efficiently attenuate synthesized and real world acoustic disturbances captured in a tilt-rotor aircraft's cabin. Finally, it can create an adequate quiet zone for gentle head movement while maintaining its stability. [ABSTRACT FROM AUTHOR]

Purpose: Aviation is an important contributor to climate change and other environmental problems. Electrification is one option for reducing the environmental impacts of aviation. The aim of this study is to provide the first life cycle assessment (LCA) results representing an existing commercial, two-seater, all-electric aircraft. Methods: An attributional cradle-to-grave LCA was conducted with a functional unit of 1 h flight time. Data and records from an aircraft manufacturer informed much of the study. Detailed modelling of important aircraft components is provided, including the battery, motor, inverter, instrument panel and seats. Impact results are compared to those from a similar but fossil fuel–based two-seater aircraft. A wide range of impact categories was considered, while the focus was on global warming, resource depletion, particulate matter, acidification and ozone formation. Results and discussion: The main contributors to almost all impact categories are the airframe, the lithium-ion battery and emissions (in the use phase). The airframe has a major impact as it contains energy-intensive, carbon fibre–reinforced composites, the impact of which can be reduced by recycling. The battery dominates mineral resource depletion categories and contributes notably to emission-based categories. Producing batteries using non-fossil energy or shifting to less resource-intensive, next-generation batteries would reduce their impact. Use-phase impacts can be reduced by sourcing non-fossil electricity. Despite the need for multiple battery pack replacements, the comparison with the fossil fuel option (based on equal lifetimes) still showed the electric aircraft contributing less to global warming, even in a high-carbon electricity scenario. By contrast, when it concerned mineral resources, the electric aircraft had greater impact than the fossil fuel based one. Conclusions: A sufficiently long lifetime is key to bringing the all-electric aircraft's environmental impacts (such as global warming) below those of fossil fuel–based aircraft. The high burden of the airframe and batteries can then be outweighed by the benefit of more efficient and emission-free electric propulsion. However, this comes with a trade-off in terms of increased mineral resource use. [ABSTRACT FROM AUTHOR]

This study is theoretically anchored in the office-seeking approach and coalition theory of political science. It is based on the most widespread theories of portfolio distribution in executive and legislative bodies (proportionality, power index, voting weights), and it tests these theories using data related to coalition negotiations in the Czech Republic for the new 2021 government coalition, a case of a surplus majority government. The study investigates the distribution of ministerial positions in the government, the office of President (Speaker) of the Chamber of Deputies, and the chairs of permanent parliamentary committees. The analysis also explores the types of electoral coalitions formed; the SPOLU coalition was a superadditive coalition, while the PirSTAN coalition was only an additive coalition. Grounded in the theory of electoral games, the Shapley-Shubik and Banzhaf power indices and the theory of coalition formation are applied in order to analyse the possible minimal winning coalitions that could be formed following the 2021 elections to the Chamber of Deputies. [ABSTRACT FROM AUTHOR]

Aviation is rapidly expanding and recovering from the pandemic impact driven by the experience economy. This is particularly subject to interfaces such as the aircraft seats, which are getting intense attention as a differentiator in the cabin. The focal point of this paper is to assess and convert customer requirements into what must be done for an optimum aircraft seat. To achieve this, a 2-step analytic hierarchy process and quality function deployment (AHP-QFD) methodology was successfully applied, consolidating product quality characteristics. Then, it leverages a novel scoring method of interdependencies to isolate dependable design variables. Consequently, safety, weight, and durability scored maximum, emphasizing backrest design and alternative composite materials, while test infrastructure was determined as a critical investment component. Furthermore, it is shown how AHP-QFD can be used for product strategy and strategic portfolio management of R&D projects. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the biomechanical mechanisms driving passengers' lower-limb postural shifts during seated sleep on a flight to prevent negative effects on passengers' physical health. Twenty subjects participated in an observational study and a subsequent experiment on fatigue development and tissue oxygenation changes during seated sleep in an economy-class aircraft seat. Three of the most frequently used postures, which involved four targeted muscles of the legs and the thigh-buttock region, were selected and examined in the experiment with the following measures: muscle electromyogram, tissue oxygenation, and body contact pressure distribution. The results showed that the fatigue of the tibialis anterior and gastrocnemius and the compression of the region under the medial tuberosities were relieved by alternations among the three positions—position 1 (placing the shanks forwards), position 2 (placing the shanks neutrally), and position 3 (placing the shanks backwards). This research reveals the mechanical properties of the biomechanical factors functioning in lower-limb postural shifts during seated sleep and provides design optimization strategies for economy-class aircraft seats to reduce the negative effects on passenger health. [ABSTRACT FROM AUTHOR]

Estimating the price elasticity of demand for air transport is essential to understand how demand responds to price variations and thus propose appropriate public policies and business strategies oriented toward this sector's sustainability in its triple aspect (economic, environmental and social). This paper aims to provide a robust quantification of the price elasticity of demand for air travel on U.S. domestic routes using quarterly data from 1996:1 to 2021:4 on these routes from the Bureau of Transportation Statistics' Airline Origin and Destination Survey. Four different samples are analyzed to ensure consistency of the estimates obtained. The estimation method and the origin of the price changes are the main contributions of this research. Estimation is conducted using a quasi-experimental method to ensure that the supply curve shifts on a stable demand curve and that measuring the response of demand to price changes enables predictions about the demand for air travel. Although previous studies have addressed this issue, this research analyses a different situation, with flexible and changing prices, in which the change in supply is due to the decisions of the companies operating in the market rather than generated by public policies and rigid pricing environments (fixed fares). An analysis of airline supply shifts is added for the selected periods and routes. The estimation shows that the demand for passenger airline seats in the analyzed context is inelastic in the lower range but within the interval of most of the estimates found in the literature. [ABSTRACT FROM AUTHOR]

Little work has been carried out to predict the comfort of aircraft seats, a component in close contact with the human body during travel. In order to more accurately predict the nonlinear and complex relationship between subjective and objective evaluations of comfort, this paper proposes a prediction method based on the Improved Particle Swarm Algorithm (IPSO) and optimized Support Vector Machine Regression (SVR). Focusing on the problems of the too-fast convergence and low accuracy of the traditional particle swarm algorithm (PSO), the improved particle swarm algorithm (IPSO) is obtained by linearly decreasing the dynamic adjustments of inertia weight ω , self-learning factor c 1 , and social factor c 2 ; then, the penalty parameter C and kernel function parameter σ of SVR are optimized by the IPSO algorithm, and the comfort prediction of IPSO-SVR is established. The prediction accuracy of IPSO-SVR was 94.00%, the root mean square error RMSE was 0.37, the mean absolute value error MAE was 0.32, and the goodness of fit R2 was 0.92. The results show that the optimized IPSO-SVR prediction model can more accurately predict seat comfort under different angles and backrest tilt angles and can provide reference and research value for related industries. The results show that the optimized nonlinear prediction model of IPSO-SVR has higher accuracy, and its prediction method is feasible and generalizable, meaning it can provide a reliable basis for the prediction of seat comfort under different angles and backrest inclinations, as well as providing reference and research value for related industries. [ABSTRACT FROM AUTHOR]

As aviation's contribution to anthropogenic climate change is increasing, industry aims at reducing the aviation climate effect. However, the large contribution of non-CO2 effects to the total climate effect of aviation and their large variability for each individual flight inhibit finding appropriate guidance. Here, we present a method for the simplified calculation of CO2 equivalent emissions, expressed using the physical climate metrics ATR100 or AGWP100, from CO2 and non-CO2 effects for a given flight, exclusively based on the aircraft seat category as well as the origin and destination airports. The simplified calculation method estimates non-CO2 climate effects of air traffic as precisely as possible, without detailed information on the actual flight route, actual fuel burn, and current weather situation. For this purpose, we evaluate a global data set containing detailed flight trajectories, flight emissions, and climate responses, and derive a set of regression formulas for climate effects, which we call climate effect functions, as well as regression formulas for fuel consumption and NOx emissions. Compared to previous studies, this method is available for a larger number of aircraft types, including most commercial airliners with seat capacities starting from 101 passengers, and delivers more specific results through a clustering approach. The climate effects calculated using the climate effect functions derived in this study exhibit a mean absolute relative error of 15.0 % and a root mean square error of 1.24 nK with respect to results from the climate response model AirClim. The climate effect functions are designed for climate footprint assessments, but would not create an incentive in an emission trading system, for which detailed information on the current weather as well as the actual flight route and profile would be required. [ABSTRACT FROM AUTHOR]

Problem Definition: This paper considers a setting in which an airline company sells seats periodically, and each period consists of two selling phases, an early-bird discount phase and a regular-price phase. In each period, when the early-bird discount seat is stocked out, an early-bird customer who comes for the discounted seat either purchases the regular-price seat as a substitute (called buy-up substitution) or simply leaves. Methodology/Results: The optimal inventory level of the discounted seats reserved for the early-bird sale is a critical decision for the airline company to maximize its revenue. The airline company learns about the demands for both discounted and regular-price seats and the buy-up substitution probability from historical sales data, which, in turn, are affected by past inventory allocation decisions. In this paper, we investigate two information scenarios based on whether lost sales are observable, and we provide the corresponding Bayesian updating mechanism for learning about demand parameters and substitution probability. We then construct a dynamic programming model to derive the Bayesian optimal inventory level decisions in a multiperiod setting. The literature finds that the unobservability of lost sales drives the inventory manager to stock more (i.e., the Bayesian optimal inventory level should be kept higher than the myopic inventory level) to observe and learn more about demand distributions. Here, we show that when the buy-up substitution probability is known, one may stock less, because one can infer some information about the primary demand for the discounted seat from the customer substitution behavior. We also find that to learn about the unknown buy-up substitution probability drives the inventory manager to stock less so as to induce more substitution trials. Finally, we develop a SoftMax algorithm to solve our dynamic programming problem. We show that the obtained stock more (less) result can be utilized to speed up the convergence of the algorithm to the optimal solution. Managerial Implications: Our results shed light on the airline seat protection level decision with learning about demand parameters and buy-up substitution probability. Compared with myopic optimization, Bayesian inventory decisions that consider the exploration-exploitation tradeoff can avoid getting stuck in local optima and improve the revenue. We also identify new driving forces behind the stock more (less) result that complement the Bayesian inventory management literature. Funding: Z. Luo acknowledges the financial support by the Internal Start-up Fund of The Hong Kong Polytechnic University [Grant P0039035]. P. Guo acknowledges the financial support from the Research Grants Council of Hong Kong [Grant 15508518]. Y. Wang's work was supported by the Research Grants Council of Hong Kong [Grant 15505318] and the National Natural Science Foundation of China [Grant 71971184]. Supplemental Material: The e-companion is available at https://doi.org/10.1287/msom.2022.1169. [ABSTRACT FROM AUTHOR]

Increased interest in the airline industry to enhance occupant comfort and maximize seating density has prompted the design and installation of obliquely mounted seats in aircraft. Previous oblique whole-body sled tests demonstrated multiple failures, chiefly distraction-associated spinal injuries under oblique impacts. The present computational study was performed with the rationale to examine how oblique loading induces component level responses and associated injury occurrence. The age-specific human body model (HBM) was simulated for two oblique seating conditions (with and without an armrest). The boundary conditions consisted of a 16 g standard aviation crash pulse, 45 deg seat orientation, and with restrained pelvis and lower extremities. The overall biofidelity rating for both conditions ranged from 0.5 to 0.7. The validated models were then used to investigate the influence of pulse intensity and seat orientation by varying the pulse from 16 g to 8 g and seat orientation from 0 deg to 90 deg. A total of 12 parametric simulations were performed. The pulse intensity simulations suggest that the HBM could tolerate 11.2 g without lumbar spine failure, while the possibility of cervical spine failure reduced with the pulse magnitude <9.6 g pulse. The seat orientation study demonstrated that for all seat angles the HBM predicted failure in the cervical and lumbar regions at 16 g; however, the contribution of the tensile load and lateral and flexion moments varied with respect to the change in seat angle. These preliminary outcomes are anticipated to assist in formulating safety standards and in designing countermeasures for oblique seating configurations. [ABSTRACT FROM AUTHOR]

According to Nobel Laureate Edmund Phelps (2013, p. 123), Mises's critique of economic calculation under socialism renders him the originator of the economic analysis of property rights. This paper also suggests that implicit to Mises's impossibility theorem was also the origins of the theory of transaction costs. This raises the following question: what is the relationship, if any, between the process of economic calculation and the concept of transaction costs? Filtered through a Misesian lens, we argue that transaction costs are the costs of engaging in economic calculation. We illustrate our theoretical point utilizing the case of airline oversales auction system first proposed by Julian Simon (1968). In doing so, we reframe the problem of airline oversales from a transaction‐cost approach, one in which property rights in airline seats are initially poorly defined. By doing so, we illustrate that resources expended to discover the valuable attributes of a good (in this case airline seats), the terms of exchange between potential trading partners, as well as enforcing the terms of an exchange, all of which are transaction costs, are also, by definition, the costs of calculating the exchange value of goods. Thus, the airlines oversales auction system is illustrative of an institutional solution to the problem of economic calculation via a reduction of transaction costs. [ABSTRACT FROM AUTHOR]

We provide a mixed-integer programming model (MIP) to assign airplane passengers to seats while preserving two types of social distancing: the distance from the passengers' seats to the aisle and the distance among groups of passengers who are not travelling together. The method assigns passengers travelling within a family group to seats near others of the same group. We present a heuristic algorithm to solve the proposed MIP. This algorithm is warm started with an initial seat assignment. Stochastic simulation experiments using the new method confirm that more passengers can be assigned safely to the seats when family groups are considered. For a certain load of passengers, as the percentage of family groups compared to singleton passengers increases, the model can practice social distancing among more passengers from different groups. The proposed model provides a superior seating assignment compared to an airline policy of blocking all middle-seats. [ABSTRACT FROM AUTHOR]

This work introduces a new approach for accelerating the numerical analysis of time-domain partial differential equations (PDEs) governing complex physical systems. The methodology is based on a combination of a classical reduced-order modeling (ROM) framework and recently-introduced Graph Neural Networks (GNNs), where the latter is trained on highly heterogeneous databases of varying numerical discretization sizes. The proposed techniques are shown to be particularly suitable for non-parametric geometries, ultimately enabling the treatment of a diverse range of geometries and topologies. Performance studies are presented in an application context related to the design of aircraft seats and their corresponding mechanical responses to shocks, where the main motivation is to reduce the computational burden and enable the rapid design iteration for such problems that entail non-parametric geometries. The methods proposed here are straightforwardly applicable to other scientific or engineering problems requiring a large-number of finite element-based numerical simulations, with the potential to significantly enhance efficiency while maintaining reasonable accuracy. [ABSTRACT FROM AUTHOR]