Publications

2018

Ground-Operational Assessment of Novel Aircraft Cabin Configurations

Schmidt, M.
Dissertation, Technical University of Munich.

This thesis focuses on the turnaround as the connecting element between airport and aircraft. A review of current research showed that only a few concepts for improved ground operational and passenger processes have been thoroughly analyzed. Since current models and frameworks are by the majority, not accessible and neither extendable, the development of a holistic assessment framework for advanced ground operational concepts was undertaken. The framework presented comprises: cabin design heuristics, agent-based passenger flow simulation, turnaround modeling and operational cost assessment. Mission performance analyses are integrated with sensitivity analysis produced with state-of-the-art aircraft design tools. The core of this research is dedicated to the development of the agent-based passenger flow simulation which has been made available for the community. The framework application covered the assessment of single- and twin-aisle configurations with passenger numbers ranging from 180 to 300. The analyzed sensitivities comprise passenger characteristics and the impact of changes to the cabin layout. Furthermore, several individual concepts were combined into two case studies aiming to capture cascading effects. The overall goal of novel cabin concepts is to allow for a seamless passenger egress and ingress through the avoidance of queues caused by aisle and row interferences. Especially, the stowing and retrieving of hand luggage items increased the average boarding time by up to 68 %. Doors should be placed near the center of the fuselage to allow for a split of the passenger stream resulting in up to 48 % shorter boarding times. The comparison of single- and twin-aisle determined an advantage of 40 % of the twin-aisle over the single-aisle. The implementation of foldable seats provided a backward compatible solution to increase the boarding effciency of up to 30%. The afore identified boarding time reduction resulted in shorter turnarounds, since the passenger processes were on the critical path. The integrated studies showed significant passenger process time savings, however those savings came with penalties in terms of higher fuel burn and maintenance cost, which almost outweigh the savings on direct operating cost level. A 1% direct operating cost improvement was identified on the 500 nm distance, where the benefit decreases for longer missions close to the design range. The findings demand further concept improvements in terms of weight, maintenance effort and the integration into current aircraft configurations. The integrated studies showed significant passenger process time savings, however those savings came with penalties in terms of higher fuel burn and maintenance cost, which almost outweigh the savings on direct operating cost level. A 1% direct operating cost improvement was identified on the 500 nm distance, where the benefit decreases for longer missions close to the design range. The findings demand further concept improvements in terms of weight, maintenance effort and the integration into current aircraft configurations.

Advancements in Passenger Processes at Airports - An Aircraft Perspective

Schultz, M. and Schmidt, M.
Transport Research Arena (TRA), Vienna, Austria

This paper provides an overview about the research done in the field of aircraft boarding focusing on fast and reliable progress. Since future 4D aircraft trajectories demand the comprehensive consideration of environmental, economic, and operational constraints, a reliable prediction of all aircraft-related processes along the specific trajectories at both air and ground is essential for punctual operations. The ground processes (aircraft turnaround) are mainly controlled by the ground handling, airport or airline staff, except the aircraft boarding, which is driven by the passengers' experience and willingness or ability to follow the proposed procedures. In this paper we provide a comparison of two model approaches to cover the individual behavior of passengers during the aircraft boarding. The implementation of two innovative infrastructural changes demonstrates the still unused potentials to further improve the boarding progress. Furthermore, the need for adapted procedures, the capabilities of a future connected cabin, and field trial results of a dynamic seat allocation are presented.

2017

Assessment of Electric Taxiing Considering Aircraft Utilization and Maintenance Cost

Kling, U., Steger, C., Peter, F. N., and Schmidt, M.
European Air & Space Conference (CEAS), Bukarest, Romania

A review of aircraft turnaround operations and simulations

Schmidt, M.
Progress in Aerospace Sciences. doi: 10.1016/j.paerosci.2017.05.002

The ground operational processes are the connecting element between aircraft en-route operations and airport infrastructure. An efficient aircraft turnaround is an essential component of airline success, especially for regional and short-haul operations. It is imperative that advancements in ground operations, specifically process reliability and passenger comfort, are developed while dealing with increasing passenger traffic in the next years. This paper provides an introduction to aircraft ground operations focusing on the aircraft turnaround and passenger processes. Furthermore, key challenges for current aircraft operators, such as airport capacity constraints, schedule disruptions and the increasing cost pressure, are highlighted. A review of the conducted studies and conceptual work in this field shows pathways for potential process improvements. Promising approaches attempt to reduce apron traffic and parallelize passenger processes and taxiing. The application of boarding strategies and novel cabin layouts focusing on aisle, door and seat, are options to shorten the boarding process inside the cabin. A summary of existing modeling and simulation frameworks give an insight into state-of-the-art assessment capabilities as it concerns advanced concepts. They are the prerequisite to allow a holistic assessment during the early stages of the preliminary aircraft design process and to identify benefits and drawbacks for all involved stakeholders.

Sizing implications of a regional aircraft for inner-city operations

Heinemann, P., Schmidt, M., Will, F., Kaiser, S., Jessberger, C. and Hornung, M.
Aircraft Engineering and Aerospace Technology, 89(4). doi:10.1108/AEAT-11-2016-0196

This technical work comprises an airport and aircraft symbiosis, designed to enable aircraft operation out of inner-city airports targeting the Advisory Council for Aviation Research and Innovation in Europe (ACARE) goals of a four hour door-to-door travel within Europe. The study is the result of an interdisciplinary group design project at Bauhaus Luftfahrt e.V. Shorter airport access and terminal processing times are seen as key enablers. During the development, a holistic view on the concept was ensured to allow the implementation in urban regions with the aim to relieve congested hub airports from direct passengers and aircraft movements and to permit faster travel times. The realization and operation within modern cities considers existing infrastructure. Space restrictions in city centers and the need for general acceptance from the public lead to demanding constraints for the overall aircraft design process. Combined with an economic market analysis, aircraft top level requirements were established that call for a low noise aircraft with Short Takeoff and Landing (STOL) capabilities. The paper describes the methodical approach and iterative procedure of the design process. A detailed concept for a 60 passenger single aisle aircraft is proposed for an Entry-Into-Service year 2040 with a design range of 1,500 nautical miles for a load factor of 90 %. Although the design for STOL and low noise operation had to be traded partly with cruise efficiency, a noteworthy reduction in fuel burn per passenger and nautical mile could be achieved against current aircraft. An assessment of potential technologies is conducted to provide the required enhancements to fulfill of the abovementioned constraints. Operational procedures were analyzed to reduce the noise propagation through flight path optimization. Furthermore a ground based assisted takeoff system was conceived to lower required takeoff field length and to prevent engine sizing just for the takeoff case. Cabin design optimization for a fast turnaround has been conducted to ensure a wide utilization spectrum. The results prove the feasibility of an aircraft developed for inner city operation.

Improving the Boarding Performance of Regional Aircraft

Schmidt, M., Heinemann, P.
2017 AIAA AVIATION Forum and Exposition, Denver, Colorado, USA. doi: 10.2514/6.2017-3424

The regional aircraft market segment is characterized by increasing competition and a high share of short flight missions below 300 nm (556 km). The turnaround process on shorter routes that can run multiple times a day becomes a competitive element for airlines. Usually passengers’ egress and ingress, together with refueling, cleaning and catering are imperative for the determination of total turnaround time. This paper evaluates modified door positions and seating concepts for regional aircraft with 50-110 seats. An operational assessment framework was applied which consists of an agent-based passenger flow simulation and a turnaround process module. A center door in the middle of the fuselage showed 9-16% shorter passenger ingress times, while a dual boarding scenario using doors located at both ends of the fuselage showed 24-32% shorter boarding times. The advantage of foldable seats with up to 53% lower boarding times is limited due to reduced space in regional cabins preventing passengers to step into the row while stowing their luggage. The maximum benefit, on a turnaround level, was identified as 3.3 minutes for 50 passengers and 5.1 minutes for 110 passengers. However, operational constraints could influence the scheduled ground time, interfering with the advantages gained in the concepts presented here. Thus, an implementation of a center door or foldable seats is questionable in the regional aircraft segment due to the small absolute time savings and the not yet accounted for additional weight and investment costs which operators face.

Optimization of Commercial Aircraft Utilizing Battery-based Voltaic-Joule/Brayton Propulsion

Isikveren, A. T., Pornet, C., Vratny, P. C., and Schmidt, M.
Journal of Aircraft, Vol. 54, No. 1 (2017), pp. 246-261. doi:10.2514/1.C033885

The intent of this investigation was to survey the potential and establish an array of technical targets for future aircraft employing hybrid-electric, battery based Voltaic-Joule/Brayton motive power systems with no additional electrical energy drawn from generators mechanically coupled to gas-turbines. Irrespective of passenger accommodation, i.e. 70 or 180 passengers, it was concluded that the tri-fan morphology (two under-wing podded gas-turbines and one aft-fuselage mounted electrically driven motor) would be an appropriate choice. Although a Battery Cell-level Gravimetric Specific Energy (referred to as “battery energy density”) of at least 1300 Wh/kg would be desirable, a less ambitious, yet still aggressive target of 900-950 Wh/kg for battery energy density was found to yield a worthwhile outcome. In terms of effecting a 15% block fuel reduction compared to a suitably projected gas-turbine only year-2035 aircraft, and, in keeping with the technical recommendations given above design range targets of 900 nm (1666 km) and 1100 nm (2037 km) for 70-passenger and 180-passenger aircraft respectively, were suggested. Finally, it was also established assuming the tri-fan morphology Normal Conducting Machines delivering shaft power output of 4.5 MW for the 70-passenger application and 8.5 MW for the 180-passenger aircraft would be required.

Boarding and Turnaround Process Assessment of Single- and Twin-Aisle Aircraft

Schmidt, M., Heinemann, P. and Hornung, M.
55th AIAA Aerospace Sciences Meeting, American Institute of Aeronautics and Astronautics, Grapevine, Texas, USA. doi: 10.2514/6.2017-1856

An efficient aircraft turnaround is an essential element for airlines to be competitive. In current short-to-medium-haul operation, passenger boarding and disembarking are key processes of an aircraft turnaround and often on the critical path. This gets amplified with the recent trend towards denser aircraft cabins and larger aircraft equipment types. Hence, new concepts for optimized passenger processes are required, such as door position permutations or seat layouts, which provide more space for passengers’ movements and them stowing luggage. To identify reduction potentials, this paper evaluates novel layout configurations and seating concepts for single- and twin-aisle aircraft with 180-300 seats. An operational assessment framework is applied which consists of an agent-based passenger flow simulation, an aircraft design part based on handbook methods and turnaround process modelling. The findings revealed that a scenario using doors positioned at 1/4 and 3/4 of the cabin length could reduce the boarding time by up to 47% for single-aisle and up to 44% for a twin-aisle configuration compared to a single door for passenger processes. Furthermore, the implementation of foldable seats into single-aisle configurations enables to outperform conventional twin-aisle concepts boarding performance by up to 12% depending on the seat concept and door configuration. The turnaround assessment could show that latter seat concepts have the potential to close the current existing time delta between single- and twin-aisle configurations from 25% to 6%. Building upon these results, an evaluation of the operational integration into current operations and airline fleets based on a direct operating cost will be feasible.

2016

Boarding Process Assessment of Novel Aircraft Cabin Concepts

Schmidt, M., Engelmann, M., Rothfeld, R. and Hornung, M.
30th International Congress of the Aeronautical Sciences (ICAS), Daejeon, South Korea.

For airlines, an efficient aircraft turnaround is an essential element to be competitive. Passenger boarding and disembarking, as key processes of an aircraft turnaround, are often on the critical path. Hence, a passenger process time reduction would also shorten the total turnaround time. Novel cabin concepts which can be adapted during boarding, such as foldable seats, provide more space for passengers’ movements and them stowing luggage. Yet, such concepts have not been investigated thoroughly, even though they promise a significant process time reduction. This paper investigates a lifting seat pan and a sideways foldable seat concept using the two- dimensional agent-based passenger flow simulation framework PAXelerate. The case studies follow the Monte Carlo approach with a probabilistic distribution of passenger anthropometrics, a variation of load factor and hand luggage to be stowed. In comparison with a reference case, a state-of-the-art short-to- medium haul aircraft with 180 seats in a six- abreast single-aisle layout, a boarding time reduction of up to 28% could be identified. This can be translated into an 11%-shorter total turnaround time, which is a significant contribution towards promoted environmental goals of international regulators.

Conceptual Studies of a Transport Aircraft Operating out of Inner-City Airports

Heinemann, P., Schmidt, M., Will, F., Shamiyeh, M., Jessberger, C. and Hornung, M.
65th Deutscher Luft- und Raumfahrtkongress 2016 (DGLR). Braunschweig, Germany.

An inner-city airport concept is proposed as a result of an interdisciplinary group design project at Bauhaus Luftfahrt, as a novel approach towards the realization of the Advisory Council for Aviation Research and Innovation in Europe (ACARE) goals of a four hour door-to-door travel. Accelerated airport and terminal processing times are seen as key enablers for the idea. Therefore existing infrastructure is used that provide the required space and connectivity. A holistic concept is conceived for application in urban regions to relieve congested hub airports from direct passengers and aircraft movements and achieve faster travel times. The paper summarizes the key requirements and constraints that are driving the design, such as the airport layout and facilities. Due to space limitations in width and length, possible aircraft concepts have to deal with short runways and need to gain acceptance of the surrounding population. This leads to an aircraft design, which is strongly coupled to the airport infrastructure and forces the requirement of a very low noise design with Short Takeoff and Landing (STOL) capabilities. A concept for an Entry-Into-Service year 2040 is proposed, that fulfils these requirements and leads to a significant reduction in fuel burn per passenger and nautical mile, for a 1500 nautical mile design range with 54 passengers, compared to a year 2000 reference. New airframe and propulsion technologies were analysed and implemented to help achieving the desired specifications. The low noise design, required for acceptance among the population in urban areas, leads to an investigation of different noise reduction technologies for airframe and propulsion systems and their interaction. Off design analysis and cabin design optimization has been conducted to ensure a wide utilization spectrum and a quick turnaround time.

Multi-Modal Transport Hub Concept for Inner-City Airport Operation

Urban, M., Jessberger, C., Rothfeld, R., Schmidt, M., Batteiger, V., Plötner, K.O. and Hornung, M.
65th Deutscher Luft- und Raumfahrtkongress 2016 (DGLR). Braunschweig, Germany.

The Advisory Council for Aviation Research and Innovation in Europe (ACARE) Strategic Research and Innovation Agenda intends maximum intra-European travel times of four hours door-to-door for 90% of passengers in 2050. However, todays’ commercial air travel is affected by several time-consuming influences which results not only in an unintended extension of the actual travel time well beyond single flight time but also increases the hassles for the passengers along the journey. In order to meet this target, Bauhaus Luftfahrt e.V. has developed an integrated transport solution during its internal Group Design Project in collaboration with Glasgow School of Arts. This transport concept consists of an inner-city airport combined with a short takeoff and landing (STOL) capable, short-range aircraft, providing capacity for up to 60 passengers. Scrum, an agile development methodology, was utilized to realize the development of both – the airport and aircraft concepts – from an initial idea within a highly constrained time scope of overall three months. This paper presents the development of the inner-city airport concept, which overbuilds city space that is currently occupied by railway tracks and features full integration into the existing rail and air traffic systems. With 16 hours of daily operations, the inner-city airport was designed for up to 10.5 million annual passengers. The building consists of four levels including the runway level on top, the apron level, located directly below the runway, a public terminal and a rail level. The roof-top runway with a length of 640 meters – combined with an aircraft elevator system and a distributed security check concept – allows for shortened overall travel times. In addition, the potential air traffic capacity increase, by introducing inner-city airports in Europe, Asia and the United States of America, was investigated to estimate the concept’s effects on existing air traffic infrastructure. However, several key challenges were identified, hereunder the additional emissions of airport operations within city centers, arising safety implications, and the required adaptation of all required ground handling and passenger processes to the self-imposed time and space restrictions. Further, potential benefits – of the multi-modal, inner-city transport hub – were examined with regards to the travelers’ and residents’ interests.

Sizing Performance Implications of a Regional Aircraft for Inner-City-Airport Operations

Heinemann, P., Schmidt, M., Jeßberger, C., Will, F., Kaiser, S. and Hornung, M.
Symposium on Collaboration in Aircraft Design (SCAD), Warsaw, Poland.

This technical work comprises an airport and aircraft symbiosis, designed to enable aircraft operation out of inner-city airports targeting the Advisory Council for Aviation Research and Innovation in Europe (ACARE) goals of a four hour door-to-door travel within Europe. The study is the result of an interdisciplinary group design project at Bauhaus Luftfahrt e.V. Shorter airport access and terminal processing times are seen as key enablers. During the development, a holistic view on the concept was ensured to allow the implementation in urban regions with the aim to relieve congested hub airports from direct passengers and aircraft movements and to permit faster travel times. The realization and operation within modern cities considers existing infrastructure. Space restrictions in city centers and the need for general acceptance from the public lead to demanding constraints for the overall aircraft design process. Combined with an economic market analysis, aircraft top level requirements were established that call for a low noise aircraft with Short Takeoff and Landing (STOL) capabilities. The paper describes the methodical approach and iterative procedure of the design process. A detailed concept for a 60 passenger single aisle aircraft is proposed for an Entry-Into-Service year 2040 with a design range of 1,500 nautical miles for a load factor of 90 %. Although the design for STOL and low noise operation had to be traded partly with cruise efficiency, a noteworthy reduction in fuel burn per passenger and nautical mile could be achieved against current aircraft. An assessment of potential technologies is conducted to provide the required enhancements to fulfill of the abovementioned constraints. Operational procedures were analyzed to reduce the noise propagation through flight path optimization. Furthermore a ground based assisted takeoff system was conceived to lower required takeoff field length and to prevent engine sizing just for the takeoff case. Cabin design optimization for a fast turnaround has been conducted to ensure a wide utilization spectrum. The results prove the feasibility of an aircraft developed for inner city operation.

Challenges for ground operations arising from aircraft concepts using alternative energy

Schmidt, M., Paul, A., Cole, M. and Plötner, K.O.
Journal of Air Transport Management. doi:10.1016/j.jairtraman.2016.04.023.

Current research in the field of future aircraft concepts aims at accommodating ambitious reduction goals set e.g. 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 aircraft requirements with current procedures, discusses the necessary adaptions to operational processes. The results highlight certain 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.

PAXelerate - An Open Source Passenger Flow Simulation Framework for Advanced Aircraft Cabin Layouts

Schmidt, M., Engelmann, M., Brügge-Zobel, T., Hornung, M., and Glas, M.
54th AIAA Aerospace Sciences Meeting, American Institute of Aeronautics and Astronautics, San Diego, California, USA. doi:10.2514/6.2016-1284

An annual uptick in air traffic of up to 5.0% challenges the involved stakeholder. Focusing on the ground operation, short passenger egress and ingress processes are an essential element of an efficient aircraft turnaround, since they constitute the critical path. A review of advanced aircraft concepts and cabin layouts revealed a lack of quantified assessment regarding their operational performance, even if they offer huge potentials for improvement with respect to overall process time. Available passenger flow simulation frameworks are limited in their application to timely adaptable cabins during the boarding procedure, such as using foldable seats, or their public availability is restricted. Tying in with this shortfall, the proposed agent-based passenger flow framework PAXelerate is especially designed to allow a flexible assessment of novel cabin architectures and ensures code accessibility due to an open source license. The simulation frameworks build upon OpenCDT containing a structured data model and graphical user interface. PAXelerate features a cabin designer, agent builder and simulation core using parallel thread processing techniques to enable a realistic agent interaction. Being validated for state-of-the-art short- to-medium haul aircraft cabin layouts, advancement regarding wide-body as well as multi-deck cabin arrangements and novel carry-on storage solutions are targeted for future improvements.

2015

Conceptual Studies of Future Hybrid-Electric Regional Aircraft

Isikveren, A. T., Pornet, C., Vratny, P. C., and Schmidt, M.
22nd International Symposium on Air Breathing Engines (ISABE), Phoenix, Arizona, USA.

The intent of this investigation was to survey the potential and establish an array of technical targets for future aircraft employing hybrid-electric, battery based Voltaic-Joule/Brayton motive power systems with no additional electrical energy drawn from generators mechanically coupled to gas-turbines. Irrespective of passenger accommodation, i.e. 70 or 180 passengers, it was concluded that the tri-fan morphology (two under-wing podded gas-turbines and one aft-fuselage mounted electrically driven motor) would be an appropriate choice.Although a Battery Cell-level Gravimetric Specific Energy (BCGSE) of at least 1300 Wh/kg would be desirable, a less ambitious, yet still aggressive target of BCGSE 900-950Wh/kg was found to yield a worthwhile outcome. The investigation also gauged the relative merits between projected Normal ConductingMotors (NCM) and emerging High-Temperature Super-conducting Motor (HTSM) technologies. It was concluded, apart from a 2-4% reduction in aircraft design weights due to HTSM, from what is known today ofoperating economics and independent of aircraft accommodation,projected NCMwas seen to be a pragmatic choice. In terms of effecting a 15% block fuel reduction compared to a suitably projected gas-turbine only year 2035 aircraft, and, in keeping with thetechnical recommendations given above design range targets of 900 nm (1666 km) and 1100 nm (2037 km) for 70-passenger and 180-passenger aircraft respectively, were suggested. Finally, it was also established assuming the tri-fan morphology NCM delivering shaft power output of 4.5 MWfor the 70-passenger application and 8.5 MWfor the 180-passenger aircraft would be required.


Novel Aircraft Ground Operation Concepts Based on Clustering of Interfaces

Schmidt, M., Nguyen, P., and Hornung, M.:
SAE Technical Paper 2015-01-2401, Seattle, Washington State, USA. doi:10.4271/2015-01-2401

The projected uptick in world passenger traffic challenges the involved stakeholders to optimise the current aviation system and to find new solutions being able to cope with this trend. Since especially large hub airports are congested, operate at their capacity limit and further extensions are difficult to realise. Delays due to late arrival of aircraft or less predictable ground operation processes disrupt the airport operations in a serious way. Various concepts improving the current turnaround processes have been presented thus far, whereby radical aircraft design changes have little chances for realisation in the short term. By maintaining the established overall aircraft configuration, the concepts promote higher probability to become commercially available for aircraft manufactures and operators. Based on a clustering of aircraft interfaces, such as doors and service panels, for state-of-the-art passenger aircraft, concepts targeting to reduce the required resources and time are presented. First studies show that relocating and installing wider passenger doors allow shortening the passenger egress and ingress process by up to 55% compared to current short-to-medium haul aircraft. From a cabin layout point of view, a merger of two galleys and spatial separation from the cabin entrance area would enable a parallelisation of de-/ boarding and catering operations which save up time to 20%. The implementation of these single improvements radically shortens the average turnaround time by almost 55% for a full-service carrier and 32% for a low-cost carrier scenario. Furthermore, weight penalties due to additional installed aircraft systems are translated into block fuel deltas of around +0.3% on a 500 nm (926 km) trip. The presented concepts promote a large improvement potential to turnaround time with minor-to-moderate aircraft modifications as well as a higher level of process robustness and thus have the potential to increase airline revenues.


Scenario-Based Life-Cycle Cost Assessment of Future Air Transport Concepts

Schmidt, M., Plötner, K. O., Öttl, G., Isikveren, A. T., and Hornung, M.
International Journal of Aviation Management, Vol. 2, 2015, pp. 167–182. doi:10.1504/IJAM.2015.072378

The aviation industry stakeholders operate in a volatile environment. Because of the long life-cycles of aircraft, the consideration of future developments is vital for the Life-Cycle Cost (LCC) assessment of aircraft concepts. Using current LCC models, a multiplicity of assumptions about the future development manipulates the results to a varying degree. Hence, a link between scenarios, as an established method for describing possible future developments, and LCC models is necessary to determine the scenario-driven LCC parameters. In order to establish this link, the relations between the key scenario factors and scenario-driven LCC parameters were mapped out during an expert workshop. Each relation of the resulting network is investigated individually and regression equations based on historical values describe the dependencies. The resulting model allows the evaluation of aircraft concepts for a variety of future scenarios. The findings of a first case study assessing the economic efficiency of the A320 and A320neo in three future scenarios reveal significant differences in direct operating cost. As a result of identifying cost drivers for different future environments, it is now possible to provide more accurate predictions about the future cost of flying. Furthermore, the established linking is a major step to forecast the net present value of a new aircraft concept during the conceptual design phase.


Impact of short- to medium-haul aircraft block time changes on airline yields

Plötner, K. O., Schmidt, M., Röhm, T., and Hornung, M.
CEAS Aeronautical Journal, Volume 6, Issue 4, pp. 599-611. doi:10.1007/s13272-015-0165-0.

According to various studies, significant reductions of mission fuel burn might be achieved by lowering cruise speeds using different aircraft technologies. The change of cruise speed will have an impact on aircraft operations, mainly on block times, airline networks and hence a possible impact on airline yields. Therefore, this paper describes the effect of changed block times on passenger demand and airline yields. The used methodology is based on the discrete choice theory and is applied to simulate passenger choice in airline networks using 2004 data from the US airline market. With a change of cruise speeds and corresponding block times, analyses showed an increase of average yields by +2 % with a decrease of block times by −10 %. With an increase of block times by +20 %, a decrease of average yields by −4 % was identified. Also non-linearities between changes of yields and load factors could be observed. Changes to yields are heavily depending on origin–destination (OD) characteristics and are mainly driven by available flight alternatives.


Determining Airport Airside Capacity Utilization: A Demand-Driven Approach

Schinwald, C., Schmidt, M., Hornung, M.
15th AIAA Aviation Technology, Integration, and Operations Conference. Dallas, Texas, USA. doi:10.2514/6.2015-2594

The global air transport system has seen significant growth rates over recent decades. International global traffic, measured in passenger kilometers at least doubled every ten years. According to the market forecasts of aircraft manufacturers and authorities, traffic is set to grow significantly. This predicted increase in demand is mainly due to the increased travel needs of the global population and a general rise in income. Since many airports around the world were unable to develop airport capacity in line with rising demand, this has resulted in widespread capacity shortages. With these considerations in mind, a continual convergence of air traffic demand and airport capacity is expected in the future. Hence ever-increasing pressure is being placed on the system. Any remaining airport capacity will become a scarce resource in certain regions. This paper presents a method whereby the capacity situation of an airport can be analyzed. In addition to an examination of the overall remaining capacity, arrival-departure slot dependency is taken into account. This additional indicator has a significant impact on the remaining usable capacity available to aircraft operators and provides more realistic results. The data used for this analysis has been extracted from the Official Airline Guide (OAG) database from 2012. In a case study, Munich’s “Franz Josef Strauss” airport is taken as the subject of analysis. The method used revealed that the two largest air traffic categories, full-service carriers using Munich airport as a hub and operating regional- respectively narrow-body aircraft face an average capacity utilization of 90%. Full service-carriers using Munich airport as a destination airport and operating heavy aircraft have the lowest capacity utilization of all segments analyzed (81%).

2014

Impact of Short-to-Medium Haul Aircraft Block Time Changes on Airline Yields

Plötner, K.O., Schmidt, M., Röhm, T., Hornung, M.
63th Deutscher Luft- und Raumfahrtkongress 2014 (DGLR). Augsburg, Germany.

Significant reductions of mission fuel burn might be achieved by various studies by lowering cruise speeds using different aircraft technologies. The change of cruise speed will have an impact on aircraft operations mainly on block times, airline networks and hence a possible impact on airline yields. Therefore, this paper describes the effect of changed block times on passenger demand and airline yields. The used methodology bases on the discrete choice theory and is applied to simulate passenger choice in airline networks using 2004 data from the US airline market. With a change of cruise speeds and corresponding block times, analyses showed an increase of average yields by +2% with a decrease of block times by -10%. With an increase of block times by +20%, a decrease of average yields by -4% was identified. Also non-linearities between changes of yields and load factors could be observed. Changes to yields are heavily depending on Origin-Destination (OD) characteristics and are mainly driven by available flight alternatives.


Profit-Based Network Level Evaluation of Aircraft Block Times

Schmidt, M., Plötner, K.O., Seitz, A., Isikveren, A.T., Hornung, M.
29th International Congress of the Aeronautical Sciences (ICAS). St. Petersburg, Russia.

For the replacement of today´s aircraft, a significant reduction of mission fuel burn and noise is targeted by various future studies to achieve promoted emission targets. A Cruise Speed Reduction (CSR) should result in significant fuel burn savings, however, also leads to network-wide implications. The framework presented in this paper goes beyond an usual aircraft fuel burn trade-off study. For a holistic evaluation of the economic impact of changed block times, different models for aircraft performance, aircraft scheduling, Direct Operating Cost (DOC) and passenger demand need to be applied. Therefore, aircraft designed for cruise speed Mach numbers (M) of M0.66- 0.82 based on ducted fan and open rotor propulsion technologies were analysed regarding their impact on block times. Based on an operational evaluation of schedule disruptions, speeds down to M0.70 seem feasible. Echoing this result, DOC analyses demonstrated the lower bound of CSR should be set to around M0.70. In contrast, taking airline yields into account, the results show that for aircraft using open rotor or turbofan propulsion technology an optimized design cruise speed is around M0.78-0.80.


Implications of Aircraft Concepts Using Alternative Energy on Ground Operation

Schmidt, M., Paul, A., Cole, M., Plötner, K.O.
18th Air Transport Research Society (ATRS) World Conference. Bordeaux, France.

Current research in the field of future aircraft concepts aims at accommodating ambitious reduction goals set e.g. by national and international regulators. These concepts should not only be investigated concerning the aircraft efficiency but also in terms of their compatibility with existing ground handling procedures and airport infrastructure requirements as these influence the overall performance of a future aircraft concept. The paper addresses this aspect focusing on case studies concerning hybrid-electric and universally-electric aircraft concepts analyzing implications on 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 considered future aircraft concepts. Anticipated challenges in aligning aircraft requirements with current procedures are stressed and necessary adaptions of operational processes are discussed. The results highlight certain adaptions of the current system that are necessary before an aircraft’s entry into service and provide a first basis for the strategic planning of the involved stakeholders.


Future Transport Ultra-Low Emissions Technology Options

Isikveren, A.T., Schmidt, M.
G.A.R.S. Workshop “Air Transport and Climate Change. Worms, Germany.

Flightpath 2050 and the Strategic Research and Innovation Agenda (SRIA) have elaborated emissions and external noise targets according to chronological waypoints. There is growing evidence that indicates for Airframe, and, Propulsion and Power Systems (PPS) the projected cumulative impact of currently active and previous European Commission and National Framework Programmes will fall around 8% short of the year 2035 target (51% CO2-emissions per passenger-km reduction) given in the SRIA document. If one extends the comparative exercise to include appreciation of SRIA 2050, there is a likelihood the outcome will be in greater deficit, namely, 15% away from the 68% CO2-emissions reduction. These observations do not include more stringent regulatory rules as well as changes to passenger anthropometry, cabin comfort and amenities in the future. Upon definition of a research framework called Ultra-Low Emissions Systems (ULESys) and by examining various combinations of Airframe and PPS technology ideas it was concluded serious consideration needs to be given to the multi-functional benefits afforded by hybrid-electric architectures. A number of so-called “Annexed Technologies” such as the C-Wing morphologies and associated adaptive structures, the Propulsive Fuselage (dedicated propulsor encircling the aft fuselage), electric taxiing, wholesale use of Carbon Fibre Reinforced Plastic, and, maximized seating density within a given cabin volume, would ameliorate performance and serve to complement any advanced electrical systems architecture utilised for hybrid-electric PPS.

2013

Contributions of Cabin Related and Ground Operation Technologies Towards Flightpath 2050

Schmidt, M., Plötner, K.O., Pornet, C., Isikveren, A.T., Hornung, M.
62th Deutscher Luft- und Raumfahrtkongress 2013 (DGLR), Stuttgart, Germany.

The vision of the European Commission (EC) for 2050 is a 75% reduction in carbon dioxide (CO2) emissions per passenger kilometer relative to the capabilities of conventional aircraft in 2000. This paper focuses on airframe related contributions to a reduction of CO2 emissions in terms of structural changes of the cabin and fuselage design. Furthermore, thus far disregarded emissions during the on-block time at the airport are considered and ground operation enhancements are presented to reduce these. For the methodical approach several separate sensitivity analyses were performed to assess the CO2 impact of cabin and fuselage modifications, in terms of higher passenger density, reduced interior weight or usage of Carbon Fiber Reinforced Plastic (CFRP) for the fuselage structure, on the basis of a narrow-body medium-to-short haul reference aircraft. Moreover, the impact of electric taxiing and reduced on- block Auxiliary Power Unit (APU) running time are investigated. The result of the investigated airframe related technologies is a 6.5% CO2 emission reduction compared to the reference aircraft and a 6.2% reduction for the ATM and ground operation. However, the reduction potential of the presented strategies is insufficient to reach to target Flightpath 2050 goals solely from the investigated areas. Hence, further studies have to be conducted to improve cabin related designs and ground operation based processes to ensure the fulfillment of the released targets.


Impact of Electrically Powered Transport Aircraft on Energy and Battery Demand for Germany

Plötner, K.O., Vratny, P.C., Schmidt, M., Isikveren, A.T., Hornung, M.
62th Deutscher Luft- und Raumfahrtkongress 2013 (DGLR). Stuttgart, Germany.

A possible Entry-into-Service (EIS) of electrically powered transport aircraft with a concept of interchangeable batteries will result in higher demand of electric energy at airports. Additionally, batteries will be introduced as new types of containers which have to be handled at the airports. Therefore, this paper focuses on the analysis of overall electric energy and battery demand for Germany as well as for each German Airport with significant passenger volumes. Furthermore, using scheduled air traffic data from 2012 leads to a first estimation of the impact of E-Aviation on electric energy demand for a specific day and the number of required batteries for each flight. Finally maximum number of batteries and housing space for recharging are identified for various recharging times including overnight charging option. Using the Bauhaus Luftahrt Ce-Liner concept as a possible replacement of today’s single-aisle aircraft like A320 and B737 families, a replacement potential of 54% for all flights from and to Germany was determined. With an electrification of future regional aircraft, the replacement potential of today’s fleet increases to 81%. Replacing all A320 and B737 operated in 2012 will lead to overall electric energy demand for Germany of 9.75TWh or 2% of the German annual electric energy consumption. Using renewable energy source like photovoltaic or wind energy, the required area exceeds the operational area for most of the German Airports, hence airports have to be included into the national and European electricity network. Various battery recharging times from one to twelve hours were investigated with their impact on maximum provided electric capacity and number of required batteries for German airports. It could be shown that longer charging times significantly increase the number of required batteries at the airport; however the maximum electric capacity decreases significantly, leading to a more balanced electric energy demand with lower peak loads. However, required housing space for batteries also increases significantly. Even if bigger airports are more constrained in their operational area, it can be assumed that battery storage at airports might not be a constraining factor for introducing E-Aviation.


Operating Cost Estimation for Electric - Powered Transport Aircraft

Plötner, K.O., Schmidt, M., Baranowski, D., Isikveren, A.T., Hornung, M.
2013 Aviation Technology, Integration, and Operations Conference, AIAA Aviation. Los Angeles, California, USA. doi:10.2514/6.2013-4281

Different international commitments in the aviation industry concerning environmental protection entail a drastic reduction of emissions in the near future. To meet these ambitious targets, research facilities and aircraft integrators work on developments of novel propulsion systems and pursue various approaches especially with hybrid and full-electric propulsion systems. Besides the technical feasibility of all these concepts, the impact of this technology on operating costs arises. To be able to understand operating cost drivers for electric-powered transport aircraft, this paper focuses on the development of an operating cost method for electric-powered aircraft and first applications. Especially, a new cost category of batteries replacing fuel as energy source was investigated in detail. Besides an assessment of costs for battery acquisition, battery lifetime including residual value and battery maintenance, the paper also reviews the development of local and global electricity prices compared to fuel prices. Regarding the impact on maintenance costs of a full-electric powered aircraft, first cost estimations for High-Temperature Superconducting (HTS) motors and associated Air Transport Association (ATA) chapters are presented. The developed cost method was applied to a full-electric aircraft concept and compared to a conventional aircraft concept, both with an expected technology level for entry into service in the year 2035. Applying today´s charging scheme to electric powered aircraft, significant higher Take-off and Landing (TOW and MLW) Weights result in higher landing and navigation charges, flight crew costs or airframe direct maintenance costs. Battery acquisition, deprecation and insurance costs raised cost of ownership by +23%. On the other side, first analysis showed that engine direct maintenance costs of HTS-motors could be lowered by nearly 34% compared to conventional turbofan architecture. Heavily influencing the final cost comparison, a 2% reduction in required energy costs was calculated taking today´s average fuel and electricity prices into account. The analysis showed a possibility – depending on energy prices and environmental charges – of cost-neutral operation of fully electric-powered aircraft compared to advanced combustion technologies with the benefit of enabling air transportation without any anthropogenic emission impact.


Scenario-Based Life-Cycle Cost Assessment of Future Air Transport Concepts

Schmidt, M., Plötner, K.O., Öttl, G., Isikveren, A.T., Hornung, M.
17th Air Transport Research Society (ATRS) World Conference. Bergamo, Italy.

The aviation industry stakeholders operate in a volatile environment. Because of the long life-cycles of aircraft, the consideration of future developments is vital for the Life-Cycle Cost (LCC) assessment of aircraft concepts. Using current LCC models, a multiplicity of assumptions about the future development manipulates the results to a varying degree. Hence, a link between scenarios, as an established method for describing possible future developments, and LCC models is necessary to determine the scenario-driven LCC parameters. In order to establish this link, the relations between the key scenario factors and scenario-driven LCC parameters were mapped out during an expert workshop. Each relation of the resulting network is investigated individually and regression equations based on historical values describe the dependencies. The resulting model allows the evaluation of aircraft concepts for a variety of future scenarios. The findings of a first case study assessing the economic efficiency of the A320 and A320neo in three future scenarios reveal significant differences in direct operating cost. As a result of identifying cost drivers for different future environments, it is now possible to provide more accurate predictions about the future cost of flying. Furthermore, the established linking is a major step to forecast the net present value of a new aircraft concept during the conceptual design phase.

2012

Scenario-Based Life-Cycle Cost Assessment of Future Air Transport Concepts

Schmidt, M.
Diploma Thesis. Technical University Munich. Munich, Germany.