Introduction
Increasing the overall fleet utilization and optimizing the gate-to-gate punctuality have been important operational goals of the air transport industry for a long time. The management of aircraft turnaround operations thereby affects the punctuality performance of turnarounds1 and consequently the overall gate-to-gate punctuality. The turnaround time is basically defined as the duration between on and off block of the aircraft. This includes the time to complete full off-loading, loading, refuelling, catering and cabin cleaning procedures2. However, most processes of the critical path defining the turnaround duration can hardly be optimized any more. This is especially the case for conventional boarding processes mainly due to cabin layout and airport infrastructure constraints during boarding and de-boarding of passengers.
Developing a passenger container, which can be fully loaded and de-loaded from the aircraft would be a potential solution for significantly decreasing the overall turnaround time. Cabin boarding - and de-boarding - as well as cleaning and catering processes would be relocated to the landside of the airport, inside the terminals, or in the case of a multi-modal container concept even to specific passenger boarding terminals e.g. downtown of world metropolises, before the complete container is moved into the aircraft. Additionally multi-modality could be reached if the container is compatible with other ground and water based means of transport. Multi-modal transport, that is using two or more transport modes for a trip between which a transfer is necessary, seems an interesting approach to solving today’s transportation problems with respect to the deteriorating accessibility of city centres, recurrent congestion, and environmental impact3.
Especially in the field of ground transportation research multi-modal transport networks have been investigated for a long time. Cargo can either be accompanied by the means of transport using more than one mode, where trailers are transported on trains or vessels, or use different modes during transit, such as containers on trucks and trains, often termed inter-modal transport. Road-rail (train-truck) and road-water (fishy-back) combinations are of major interest4 and already exist, especially for cargo transport. Within the field of passenger transportation multi-modality can be referred to as the ability to seamlessly switch between transport types with limited waiting times and smooth transitions5. However, efficient multi-modality between air and ground based transportation both, for cargo and passenger application, has (hardly) not been realized yet. This is mainly due to the fact that weight, space and structural limitations hamper the application of containers within an aircraft. Although conventional aircraft cargo containers are already used for several decades, they cannot be efficiently used in a multi-modal transport system, because they are solely optimized for aircraft application primarily due to weight and space constraints.
In case of the proposed idea of a multi-modal passenger container, one has to be aware that the integration of such a container will certainly have a big influence on the aircraft design and structure as well as on airport design, and therefore poses a great technical challenge. First approaches for a passenger airplane container system that comprises a pod can be found in the US patent Passenger Airplane Container System6 (see FIG. 1).
FIG. 1: Passenger Airplane Container System [US Patent 64944404]
Another useful example, but with different objectives, demonstrates possible additional benefits of a passenger container concept: The Airplane Safety Body Passenger Compartment7 (see FIG. 2). In this patent “an airplane safety body passenger compartment is provided which contains a mechanism for ejecting the passenger compartment from an elongated receptacle in the fuselage when an airplane is in danger of crashing so that the parachutes will gently float the passenger compartment to the earth.”
FIG. 2: Airplane Safety Body Passenger Compartment [US Patent 4699336]
These two concepts could stimulate the future development of the proposed multi-modal passenger container. However, before detailed studies concerning the technical realization will be started, the operational benefits of the proposed system for airlines as well as airports, public transport networks and of course passengers should be investigated during a phase of incubation of the idea. The challenges for implementing such a system can be exemplary shown by the concept of mobile lounges, which are currently used at certain airports, but proved to be not very successful (see FIG. 3).
FIG. 3: Mobile lounges are currently used at certain airports, however they haven't become widely accepted
Benefits to the Air Transport System
As the air transport demand will strongly grow over the next decades8, an increase of flight delays in the global air transport system has to be countervailed. Coping with airport congestion issues will certainly stay of major importance. The optimization of current, conventional airport processes has almost reached a limit. Only radical changes within the ATM system as well as ground handling procedures will allow additional capacity improvements without systematically increasing the number of runways or the airport infrastructure. The proposed idea of a multi-modal passenger container shows the opportunity of further improving airport ground handling or rather turnaround processes and therefore helps to alleviate the congestion challenge.
Nowadays, typical turnaround times lie in the area of 30 minutes for single-aisle short range aircraft like the A3209, 75 minutes for twin-aisle long range aircraft like the A340-50010 and up to 90 minutes and more for the A38011 (see FIG. 4). The critical path is thereby defined by the time needed for de-boarding and boarding as well as refuelling of the aircraft, whereas refuelling is not allowed while passengers are on board the aircraft (with some exceptions).
FIG. 4: Exemplary turnaround diagram for the Airbus A380 using two bridges and standard servicing via main and upper decks [source Airbus S.A.S.].
The proposed concept of a passenger container will potentially allow minimizing the required time for de-boarding and boarding and therefore decreasing the overall turnaround time between approximately 10 and 25 minutes depending on the aircraft size. This will cause additional gate capacities at the airport as well as financial benefits for the airlines due to increased aircraft utilization. Additionally a multi-modal system will help to further optimize ground traffic flows to and from the airport. Since refuelling of aircraft demands most of the time during turnaround, one could also think about fuel tank modules, which potentially would further improve aircraft handling.
Likelihood of Public Acceptance
Using a multi-modal passenger cabin system will positively affect both, the travelling and non travelling public. Boarding and de-boarding processes will be faster and more convenient for passengers, as long as getting into the container doesn't have to happen a long time before the flight. Thus, it has also to be studied where people will have to get in the container, in the airport or at specific boarding terminals downtown? Also the question has to be addressed if the different logistics that would be used for the passenger capsule might impose unwelcome changes on some passengers or not. For example, if the intermodal system would make a longer abidance at the airport gate impossible, some passengers could miss the "shopping experience" before the flight. This will also have an impact on airport non-aviation revenues. The introduction of a multi-modal transport system connecting air and ground transport will potentially reduce ground traffic to and from the airport as well as local airport emissions.
Radical Content
The introduction of the proposed multi-modal passenger container will require radical changes of aircraft, airport and ground transportation systems. The philosophy of boarding and de-boarding inside the airport or even at specific passenger boarding terminals e.g. downtown of world metropolises poses a totally different system compared to today’s aircraft turn-around processes. Aircraft, airports as well as ground and water based transportation will have to be strongly adjusted in order to enable an implementation of the revolutionary multi-modal concept. If successfully implemented the concept promises radical efficiency improvements in the sectors of ground handling as well as passenger flows to and from the airport.
Credibility of the Physics
Although the execution of the idea will bring up several technical issues, the physics of law will in no case be in doubt. The aircraft design for integrated passenger containers sets mainly a technical challenge (e.g. criticality of aircraft weight), whereas the multi-modal traffic system involves operational hurdles based on existing infrastructure constraints (e.g. vehicle dimension for integration in road or rail systems).
Criteria for Successful Incubation
The main purpose of the multi-modal passenger container concept is the improvement of aircraft turn around as well as airport transfer connection efficiency. Clearly there are major implications for aircraft design related to the concept, but these should be in this stage of a downstream nature. During the incubation phase the operational benefits for the proposed system for airlines as well as for airports and public transport networks have to be investigated. Finally those benefits have to be assed in order to find an configuration (number of total passengers in the aircraft, size and number of containers, etc.)
The following key questions have to be answered in order to enable a successful incubation. It is also mentioned how these key elements might be demonstrated or measured.
1. How is the potential turnaround time decrease depending on the aircraft size?
An analysis of real airport aircraft handling data will support the derivation of the economy of time potential if the boarding and de-boarding of passengers as well as catering and cleaning processes take place “outside the aircraft”. Thus, an important part of the incubation study should be to find out for how much of the aircraft fleet the idea is useful.
2. What is the potential benefit for airlines and airports if the turnaround time is radically decreased?
Comparing the Low Cost Vs Regular Airlines Business Model demonstrates that a reduced turnaround time and a resulting higher utilization has benefitial financial advantages for an airline. Thus, answering this question requires an analysis of airline flight schedules and its potential impact on airline revenues as well as airport capacity if flight frequencies (per day or week) could be increased through shorter turnaround times. Also other criteria like passenger service and runway utilisation have to be assessed?
3. What operational and infrastructural changes would be required for airport operators?
This question demands a close look at current airport operational and infrastructural aspects as well as an analysis of requirements for the infrastructural integration of the proposed multi-modal container system.
4. How could the concept be integrated into a multi-modal airport transfer connection network to and from major city centres?
An analysis of and comparison with existing ground transportation research studies on multi-modal transport concepts will support finding feasible answers to the question where people will have to get in the container to improve the overall system. Could there be a number of containers going to/from different locations and linking to the same aircraft?
Timescale for Incubation
A period of two years will be necessary to achieve demonstration of the key feasibility points above.
Budget required for Incubation
A budget of 300000 € (two university researchers for two years) might be needed to accomplish the aims of incubation.
Partnering needs for Incubation
The partnering of an aeronautical engineer with expertise on the overall air transport system including airline and airport operations together with the knowledge of a transportation engineer will enhance the chance for successfully incubating the concept. While the aeronautical engineer could focus on operational airline aspects (questions 1 & 2 above) a transportation engineer will more likely be able finding answers to the questions 3 & 4 above dealing with airport operation in combination with ground transportation network aspects.
Related and Supporting Capabilities
The proposed concept will require changes in the aircraft and the airport systems. Clearly there has to be some mechanism for lifting or moving the pod from the airport or other place to the aircraft and installing it into its position there. Also the catering links have to be amended as well as issues of security and ID, but these seem to be much less difficult. The airport would need to be designed or adapted to use this system and the design might make it difficult to run the airport in a conventional way. Similar considerations apply to land-based transport modes.
Scalability of the Idea
The future implementation of the proposed concept of a multi-modal passenger container will certainly require dramatic technical and infrastructural changes of the aircraft, the airport and the airport connection system. At a first stage the passenger container system could be established only within the airport boundaries before it could later be expanded as a multi-modal system connecting air and ground transportation.
Thus, this idea is not very scalable insofar as it can only operate if at least five criteria are met:
1. Some land based transport system can use the containers at departure end
2. Departure airport can handle these containers
3. Aircraft between two points can handle them
4. Arrival airport can handle them
5. Arrival land transport can handle them
These aircraft could certainly also be handled conventionally at airports without the specific multi-modal or container handling infrastructure. In this case however all propable disadvantages of the concept (e.g. aircraft weight penalty) have to be taken into account.
Going up from this means adding new airports and land transport to the population of adapted places. The idea cannot be introduced more gradually than this. It will also bring some inflexibility into the operating equation as the conventional and multi-modal pods are not conceptually intermixable. It is these issues and their consequences and implications that could be dealt with in these two parts.
Finally, one of the key scalability issues will surely be the need to design and produce new aircraft to carry the containers. Consequently, fleet renewal times will be a key factor in order to succesfully integrate such a new and revolutionary system.
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