Aircraft turnaround time estimation in early design phases: Simulation tools development and application to the case of box-wing architecture

This work deals with the problem of estimating the turnaround time in the early stages of aircraft design. The turnaround time has a significant impact in terms of marketability and value creation potential of an aircraft and, for this reason, it should be considered as an important driver of fuselage and cabin design decisions. Estimating the turnaround time during the early stages of aircraft design is therefore an essential task. This task becomes even more decisive when designers explore unconventional aircraft architectures or, in general, are still evaluating the fuselage design and its internal layout. In particular, it is of paramount importance to properly estimate the boarding and deboarding times, which contribute for up the 40% to the overall turnaround time. For this purpose, a tool, called SimBaD, has been developed and validated with publicly available data for existing aircraft of different classes. In order to demonstrate SimBaD capability of evaluating the influence of fuselage and cabin features on the turnaround time, its application to an unconventional box-wing aircraft architecture, known as PrandtlPlane, is presented as case study. Finally, considering standard scenarios provided by aircraft manufacturers, a comparison between the turnaround time of the PrandtlPlane and the turnaround time of a conventional competitor aircraft is presented.     

A fast airplane boarding strategy using online seat assignment based on passenger classification

The minimization of the turnaround time, the duration which an aircraft must remain parked at the gate, is an important goal of airlines to increase their profitability. This work introduces a procedure to minimize of the turnaround time by speeding up the boarding time in passenger aircrafts. This is realized by allocating the seat numbers adaptively to passengers when they pass the boarding gate and not before. Using optical sensors, an agility measure is assigned to each person and also a measure to characterize the size of her/his hand-luggage. Based on these two values per passenger and taking into account additional constraints, like reserved seats and the belonging to a group, a novel seat allocation algorithm is introduced to minimize the boarding time. Extensive simulations show that a mean reduction of the boarding time with approximately 15% is achieved compared to existing boarding strategies. The costs of introducing the proposed procedure are negligible, while the savings of reducing the turnaround time are enormous, considering that the costs generated by inactive planes on an airport are estimated to be about 30 $ per minute.     

Aircraft operational costs and turnaround efficiency at airports

The aim of this paper is to investigate the relationship between flight schedule punctuality and aircraft turnaround efficiency at airports, in order to minimise system operational costs and meanwhile to maintain a required level of schedule punctuality. Investigations of aircraft operational costs, passenger delay costs and airline schedule time-opportunity costs are carried out in this paper. A mathematical model is applied to simulate aircraft turnaround operations by considering the stochastic effects of schedule punctuality as well as aircraft turnaround performance. Two numerical examples demonstrate the performance of the aircraft turnaround model. Results show the significance of a proper use of schedule buffer time in maintaining schedule punctuality performance.     

Resilience of passenger boarding strategies to priority fares offered by airlines

Increased efficiency of airplane boarding via the jetway is achieved by sequencing passengers at the airport terminal. Various strategies have been developed and implemented at airports. However, even the best strategy can be distorted by the airlines priority fare. Priority passengers board in a random order which destroy the desired boarding sequence. This causes the aircraft aisle to be blocked in different locations. The article analyses the sensitivity of most common boarding strategies to the number of priority passengers. The article gives an example for Airbus A320 with single aisle cabin, configured in 30 rows of 6 seats each. To investigate this issue an original simulation model was developed, which allows to estimate the impact of the number of passengers with priority on the implementation of selected boarding strategies. The results obtained are astonishing. Such distortions have a negative impact on some strategies, while for some strategies better results are obtained. This discrete event based simulation model allows the process manager to choose the appropriate strategy or to abandon the jetway and use the airport stairs to avoid or reduce delaying the aircraft.     

From passenger growth to aircraft movements

Airlines are able to deal with passenger growth by either increasing the frequency or the aircraft size, which may entail different numbers of aircraft movements. Forecasting the latter is necessary for evaluating technologies, approaching future emissions or anticipating capacity constraints. Purpose of this paper is to forecast a typical fleet mix and the growth of aircraft movements on flight segments worldwide based on an assumed passenger growth. The methodology is implemented in a model called Forecast of Aircraft Movements. Basic approach is the assignment of each flight segment worldwide to a distance, passenger number and aircraft category. For each combination of distance and passenger numbers a typical fleet mix is defined. The forecasted worldwide growth of passenger demand and the empirically determined fleet mix is applied to all segments in order to derive a future scenario. Assuming a certain seat load factor, the frequency growth can be deduced from the aircraft movements generated for all segments. The paper includes a forecast for aircraft movements in a future scenario based on real schedule and passenger data and gives a detailed overview of the methodology and results considering airlines' behaviour.     

Impacts of COVID-19 on aircraft usage and fuel consumption: A case study on four Chinese international airports

COVID-19 pandemic starting in early 2020 has greatly impacted human and industrial activities. Air transport in China shrank abruptly in February 2020, following a year-long gradual recovery. The airline companies reacted to this unprecedented event by dramatically reducing the flight volume and rearranging the aircraft types. As the first major economy that successfully controls the spread of COVID-19, China can provide a unique opportunity to quantify the medium-long impacts on the air transport industry. To quantify the corresponding changes and to elucidate the effects of COVID-19 in the wake of two major outbreaks centered in Wuhan and Beijing, we analyze twelve flight routes formed by four selected airports, using the Automatic Dependent Surveillance-Broadcast (ADS-B) data in 2019 and 2020. Our results show that the total flight volume in 2020 reduced to 67.8% of 2019 in China. The recovering time of flight volume was about 2–6 months, dependent on the severity. In order to unwind the severe challenge, airlines mainly relied on aircraft B738 and A321 between February and June in 2020 because the fuel consumption per seat of these two aircraft types is the lowest. Besides, fuel consumption and aircraft emissions are calculated according to the Base of Aircraft Data (BADA) and the International Civil Aviation Organization's Engine Emissions Databank (ICAO's EEDB). At the end of 2020, the ratios of daily fuel consumption and aircraft emissions of 2020 to 2019 rebounded to about 0.875, suggesting the domestic commercial flights were nearly fully recovered. Our results may provide practical guidance and meaningful expectation for commercial aircraft management for other countries.     

Fuel burn rates of commercial passenger aircraft: variations by seat configuration and stage distance

Aircraft fuel consumption is a very large component of airline costs. Fuel burn is also very important because it is highly correlated with emissions and contributes directly to transport externalities. This paper calibrates fuel burn in kilos per seat per nautical mile for aircraft using the EMEP/EEA aircraft inventory database. We then employ the model with OAG flight schedule data to evaluate fuel burn by flight routes and aircraft types at a global scale. The paper shows comparative fuel use among different distance based markets as well as among a variety of routes in the long-haul market. The results show geographical heterogeneity of fuel burn rates among a variety of routes, while controlling for seat configuration and stage distance. The paper finds that stage lengths centered on 1500–2000 NM have the lowest fuel burn rates under current technology, fleet composition, and seat configuration. These findings, together with comments on the viability of long range flights provide better understandings not only for the carbon taxation debates but also for operational efficiency of current aviation markets. The lower rates for moderate distance flights seems to favor networks without extreme links, and supports the use of a hub connection scheme.     

A dynamically optimized aircraft boarding strategy

Airline carriers, airports and passengers have common interests in expediting the aircraft boarding process for economical, operational, and customer satisfaction reasons respectively. Several boarding strategies have been proposed in the literature aiming to reduce the boarding time. Several theoretical models were able to achieve near optimum performance, but ignored the important aspect of allowing family and groups to board together in cliques. Some other models achieved top performance by pre-assigning passengers to seats, which deprived them from the essential privilege of choosing their own seats. The Dynamically Optimized Boarding strategy is proposed to shorten the boarding time, reduce on-board interferences, and allow passengers' cliques to proceed together to their reserved seats. Passengers are sequenced in a boarding queue based on their seats' positions, associated cliques, and the possibility of interferences, immediately after the last check-in. They are required to board the aircraft according to their positions in the queue. A technology-aided announcement process can help in guiding batches of passengers to a small pre-boarding area in order to aggregate before boarding the aircraft. A simulation-based study showed that the proposed strategy achieved a near-optimum performance without breaching the passengers' right to walk in cliques to their preferred seats.     

Airline ground operations: Optimal schedule recovery with uncertain arrival times

Airline operations are subject to a number of stochastic influences which result into variable ground and block times for same flights on different days. Our research explores how airline operations control centers may benefit from an integrated decision support system for schedule recovery during aircraft ground operations. In this paper, we study the sensitivity of an optimal set of schedule recovery options towards uncertain arrival times. The calculation of recovery options is based upon an integrated and iterative scheduling and optimization algorithm, which incorporates uncertainties for arrival flights as a function of a given look-ahead time. Potential recovery options include stand re-allocation, quick-turnaround, quick passenger transfer, waiting for transfer passengers, cancellation of passenger or crew connections, and arrival prioritization. Within a case study setting at Frankfurt Airport, 20 aircraft turnarounds are analysed during a morning peak with their respective estimated arrival times (including potential arrival delays). The analysis of simulation results reveals an almost identical set of selected recovery options under high uncertainty circumstances and from post-operational point-of-view, which indicates high solution stability.     

Reducing the effect of passengers’ non-compliance with aircraft boarding rules

The quest for efficient aircraft boarding strategies continues to generate lots of business and scientific discussions. Boarding strategies define rules and procedures aimed to reduce boarding time and operational cost. Most of the proposed strategies do not account for passengers’ non-compliance with boarding rules. Non-compliance is one of the major non-deterministic problems that can degrade any performance improvement to be expected from adopting a boarding strategy. To that, it is of paramount interest to shed light on this problem and introduce approaches for mitigating any related performance degradation in the boarding process. Although some recent research investigations considered the effect of non-compliance on the overall boarding time under different strategies, there was a lack of remedial actions. This paper dissects the operational characteristics of the non-compliance activity, proposes two different intervention approaches to deal with non-complying passengers, and analyzes the resulting impact under different categories of boarding strategies using a cellular-automaton-based simulation.     

Challenges for ground operations arising from aircraft concepts using alternative energy

Current research in the field of future aircraft concepts aims at accommodating ambitious reduction goals set by national and international regulators. These concepts should be investigated not only with regard to aircraft efficiency, but also in terms of their compatibility with airline operations, existing ground handling procedures and airport infrastructure requirements, as these influence the overall performance of a future aircraft concept. This paper addresses this aspect, focusing on case studies concerning hybrid-electric and universally-electric aircraft concepts, analyzing implications for current ground handling operations at the airport. Current bottlenecks, such as capacity shortages, and potential areas of improvement are identified based on a state-of-the-art reference ground handling process. To this end, requirements of different stakeholders, including airports, airlines and ground handling providers, are outlined. In the next step, insights are contrasted with operational requirements of the future aircraft concepts under consideration. The paper stresses the anticipated challenges involved in aligning future aircraft requirements with current procedures, discusses the necessary adaptions to operational processes. The results highlight changes that need to be made to the current system before an aircraft can enter service, and provide an initial basis for the strategic planning of the stakeholders involved.     

A multi-time scale management structure for airport ground handling automation

The sustainability of air travel relies on proper and timely aircraft ground handling at airports. This research proposes a ground handling management structure which allows the automation of operations to face the growing demand for this service. It is shown how at operations level, information exchange with the airport collaborative decision-making system turns possible on-line fleet assignment to ground handling tasks. This is done by designing different heuristics for assignment of fully automated or semi-automated vehicles to ground handling tasks. Numerical results for an actual airport are presented to illustrate the potential performance of automated ground handling operations.     

Scheduling aircraft take-offs and landings on interdependent and heterogeneous runways

This paper presents an optimization method for the aircraft scheduling problem with general runway configurations. Take-offs and landings have to be assigned to a runway and a time while meeting the sequence-dependent separation requirements and minimizing the costs incurred by delays. Some runways can be used only for take-offs, landings, or certain types of aircraft while schedules for interdependent runways have to consider additional diagonal separation constraints.Our dynamic programming approach solves realistic problem instances to optimality within short computation times. In addition, we propose a rolling planning horizon heuristic for large instances that returns close-to-optimal results.     

Assessing the suitability of airport ground handling agents

Aircraft ground handling is an essential part of an air operation and determines its punctuality and safety. Ground support equipment vehicles (GSE) are used in most of the handling tasks. This puts certain requirements on the candidates for ground handling agents, especially on their psychophysical features. This study aimed at determining a professional profile of the candidate, defining expectations and requirements for the future employee and developing a quantitative method of assessing suitability for work as a GSE operator. Since some features characterizing the employee are not measurable, and the relations between features are imprecise and often subjective, fuzzy models based on linguistic variables were used to build the assessment method. A computer implementation of the fuzzy inference system was used for the assessment of exemplary candidates for the position of fuel tanker operator. The obtained results show that the applied approach makes it possible to easily compare the candidates’ suitability for work at this position. The simulation experiments also showed that the method allows for the creation of individualized training programs based on partial assessments of individual traits of candidates.     

Experimental test of airplane boarding methods

We report the results of an experimental comparison of airplane boarding methods. This test was conducted in a mock Boeing 757 fuselage, located on a Southern California soundstage, with 12 rows of six seats and a single aisle. Five methods were tested using 72 passengers of various ages. We found a significant reduction in the boarding times of optimized methods over traditional methods. These improved methods, if properly implemented, offer the potential for significant savings to airline companies.     

A new model of luggage storage time while boarding an airplane: An experimental test

The boarding process is on the critical path of the turn-around. Reduction in boarding time can benefit airline carriers and airports and improve passenger satisfaction. However, aisle interference caused by passengers placing their luggage during boarding is a key factor leading to cabin congestion and low boarding efficiency. Therefore, the storage time for the carry-on luggage and its influencing factors is analyzed in this study. An experiment was conducted in a B737-800 model (1/3 size) to explore the factors effecting the time of luggage storage, and a new effective model of luggage storage time is proposed through a significance test and data fitting. The results show that the age of passengers, the type and quantity of luggage, and the existing luggage in the luggage bin have a significant impact on the luggage storage time; the rule of the variation in luggage placing time is similar between young adult passengers and middle aged passengers; the impact of the existing luggage in the overhead bin on the luggage storage time shows a stable trend in the initial period, but with the quantity of the luggage increasing to a certain point, the luggage storage time begins to increase sharply, which is known as a “jump”; and the luggage type has a great influence on the threshold value of jump. The results of the study can provide a reference for airlines to manage cabin luggage to improve boarding efficiency and improve passenger experience.     

Modelling of aircraft rotation in a multiple airport environment

The objective of this paper is to develop a simulation model to simulate aircraft rotation in a multiple airport environment. The developed aircraft rotation model (AR model) consists of two sub-models, namely the aircraft turnaround model, which describes the operation of aircraft turnaround activities at an airport and the Enroute model, which simulates the enroute flight time of an aircraft in the airspace between two airports. Delays due to operational disruptions from aircraft turnaround activities are modelled by stochastic variables in the aircraft turnaround model. Uncertainties from schedule punctuality are modelled by probability density functions in the Enroute model. The proposed aircraft rotation model is employed to carry out a case study by using real schedule and punctuality data from a European schedule airline. Simulation results when compared with observation data validate the effectiveness of the aircraft rotation model. The proposed model is also found suitable for airlines to serve as a schedule planning and analysis tool.     

铁路列车统一补票系统架构优化及演进

铁路列车统一补票系统是列车客运作业的重要组成部分,其易用性直接关系到列车旅客的服务质量。通过分析原有铁路列车补票系统中列车移动补票终端,由于各厂家独自研发而导致的业务功能、网络架构、数据格式以及业务管理不统一等问题,提出了铁路列车统一补票系统,实现了总体架构及网络架构等方面的优化与改进,并从系统总体工作流程、地面管理部分功能及列车移动补票终端3部分解析系统功能,明确铁路列车统一补票系统架构演进过程中的细节优化之处,并剖析此过程中涉及的数据安全、补票票价计算及交易完整性等关键技术。铁路列车统一补票系统进一步为列车客运服务提质增效提供系统支撑,系统成果也提高铁路客票系统的席位利用率。     

铁路列车统一补票系统架构优化及演进

铁路列车统一补票系统是列车客运作业的重要组成部分,其易用性直接关系到列车旅客的服务质量。通过分析原有铁路列车补票系统中列车移动补票终端,由于各厂家独自研发而导致的业务功能、网络架构、数据格式以及业务管理不统一等问题,提出了铁路列车统一补票系统,实现了总体架构及网络架构等方面的优化与改进,并从系统总体工作流程、地面管理部分功能及列车移动补票终端3部分解析系统功能,明确铁路列车统一补票系统架构演进过程中的细节优化之处,并剖析此过程中涉及的数据安全、补票票价计算及交易完整性等关键技术。铁路列车统一补票系统进一步为列车客运服务提质增效提供系统支撑,系统成果也提高铁路客票系统的席位利用率。     

Grounded aircraft: An airfield operations perspective of the challenges of resuming flights post COVID

The global COVID pandemic, national lockdowns and unprecedented decline in passenger demand worldwide has led to airlines cancelling services, furloughing staff, applying for financial support and placing aircraft into temporary storage. However, with finite space available, and up to two-thirds of the world's total passenger fleet grounded for an indeterminate period of time, airlines have been forced to park their aircraft in unusual places, sometimes at airports they do not normally serve and in volumes never normally experienced. The aim of this paper is to investigate the extent of grounded aircraft at UK airports and explore the challenges, from an airfield operations perspective, of resuming flights post-COVID.