Resilience in air transport
ComplexWorld Position Paper (December 2012) - Click to download
This section addresses the research theme “Resilience in Air Transportation”. Resilience is a fundamental property of the natural ecosystem that enables quick recovery after numerous disturbances occurring frequently. This vital ability of the ecosystem makes resilience a very desirable property of man-made socio-technical systems like an air transportation system.
Forms of defining resilience in the literature
The term resilience has been introduced first by Hoffman  in the field of mechanics and material testing in 1948. One decade later Holling  implemented the term in ecology. Currently the topic of resilience is widely spread and extensively studied. Up to the present time plenty of papers and books have been published on resilience, covering different research domains. For instance, the works          serve a good representation of the various interpretations or forms to define resilience. In the different research domains, these forms have been termed as engineering resilience, ecological resilience and resilience engineering.
The first form - engineering resilience - defines resilience as the time required for a system or as the ability of a system or as the capability of a substance to return to an equilibrium or steady-state or original state, following a disturbance or some time later after the removal of the disturbance factor    . It should be noted that Hoffman  uses the term resiliency to describe this inherent ability of a substance whereas under resilience a more extensive property which takes into account the size and shape of the object as well, is formulated.
The second form - ecological resilience - determines resilience as the ability or as the capacity of a system to absorb a disturbance, whilst essentially retaining the same function, structure, identity and feedbacks     .
The first form of definition assumes the persistence of single or global equilibrium or stable state whereas the second form proposes multiple equilibrium or stable states.
Oxford Dictionary  gives the following definitions of the terms resilient and robust:
- resilient (adjective)
- (of a substance or object) able to recoil or spring back into shape after bending, stretching, or being compressed;
- (of a person or animal) able to withstand or recover quickly from difficult conditions;
- robust (adjective)
- (of an object) sturdy in construction;
- strong and healthy; vigorous;
- (of a system, organization, etc.) able to withstand or overcome adverse conditions;
- uncompromising and forceful;
- (of wine or food) strong and rich in flavor or smell.
- (of an object) sturdy in construction;
Hence, it may be stated that engineering resilience tends semantically to resilience and ecological resilience inclines to robustness. A well structured overview on robustness or ecological resilience can be found in .
The third form - resilience engineering - has been introduced by Hollnagel et al.  in 2006. It investigates human and organizational aspects with regard to the design of safety critical socio-technical systems. Resilience engineering is a paradigm for safety management that focuses on how to help people to cope with complexity successfully when exposed to pressure. In the White Paper on Resilience Engineering for ATM, in 2009 EUROCONTROL  has provided the following definition of resilience: Resilience is the intrinsic ability of a system to adjust its functioning prior to, during, or following changes and disturbances, so that it can sustain required operations under both expected and unexpected conditions.
In various domains the terms resilience and robustness have been defined and redefined many times. Even within the same domain there exist different particular meanings. The following table
|used in synonymic sense||resilience||stability|
provides a summary of terms found in the literature which are used synonymously.
This section is based on 
Concepts of resilience in the air transportation context
The realization of the performance targets set by SESAR  incorporates the incremental step approach of three operational phases. This encompasses the time based operations, trajectory based operations and performance based operations, which are aligned with the SESAR definition of the service levels 2, 3 and 4. The third operational phase, performance based operations, aims to implement an European high performance, integrated, network-centric and collaborative and seamless air ground ATM System. To achieve the performance goals, network operations will be planned collaboratively, using a system wide information management. Performance based operations of the ATM System can be seen as the method of resolution to realize the political and socio-economical expectations of the ATM System in future.
The ATM System as a socio-technical system is driven by economic interests of the participating stakeholders. Hence, it is performance oriented. Its performance is evaluated by means of key performance indicators, which are, for instance, delay, throughput, punctuality. Key performance indicators, defined by ICAO, are assigned to 11 key performance areas (KPAs). They encompass safety, security, environmental impact, cost effectiveness, capacity, flight efficiency, flexibility, predictability, access and equity, participation and collaboration, interoperability. KPAs are a way of categorizing performance subjects related to high-level ambitions and expectations. Disturbances like the hurricane Sandy, which in 2012 caused massive disruptions in the air transportation systems, not only in North America but also in Europe, affect the continuous realization of performance targets. Generally, disturbances deteriorate the performance of the ATM System, which state expressed by performance indicators undergoes undesirable changes. By means of investigating resilience and robustness as system properties, one is able to mitigate negative impacts on performance.
When focusing on the aspects of a performance based approach for investigating resilience of an ATM System that is experiencing disturbances and being provided that safety is given at any time, the definition in , derived from the safety science perspective, did not appear sufficient enough for achieving this goal. Because of the simultaneous existence of engineering resilience and ecological resilience and various interpretations of resilience and robustness in different research domains as well, it was necessary to develop a new concept of resilience and robustness with respect to an ATM System. It has to be stressed that a clear differentiation between both terms had to be accomplished, as well as definitions had to be made to enable measurement of the terms. Moreover, in literature, exist many contradictory applications of the terms disturbance, stress and perturbation. So, it was necessary to clarify their particular meaning in the context of ATM. Taking into account the aims mentioned above, a framework, which incorporates a concept of the interdependencies between robustness, resilience and other relevant terms, has been developed in  . In this new framework the terms of disturbance, stress and perturbation are linked together to create a new terminology of resilience and robustness in the context of a socio-technical system. There, the term disturbance is defined as a cause, whereas stress and perturbation have been determined as an effect caused by a disturbance. The idea to this logical differentiation of the terms disturbance, stress and perturbation is originated in ecosystems.
Depending on a perspective - safety or performance - there are two concepts of resilience in the air transportation context:
This section is based on 
This section is devoted to describing recent research results that are relevant to the research theme of resilience in air transport. If you have any related results that you wish to contribute, please feel free to add your contribution as a subsection below. Also consider linking your results with relevant portions of the main text of the article and/or other articles (e.g. related research lines) to increase its visibility and help give it a context inside the research theme.
- R.M. Hoffman, A generalised concept of resilience, Textile Research Journal 18(3): 141-148, 1948
- C.S. Holling, Resilience and stability of ecological systems, Annual Review of Ecology and Systematics 4: 1-23, 1973, URL: http://www.annualreviews.org/doi/pdf/10.1146/annurev.es.04.110173.000245
- F.S. Brand and K. Jax, Focusing the meaning(s) of resilience: resilience as a descriptive concept and a boundary object, Ecology and Society 12(1): 23, 2007, URL: http://www.ecologyandsociety.org/vol12/iss1/art23/
- L.H. Gunderson, Ecological Resilience - in Theory and Application, Annu. Rev. Ecol. Syst., 31: 425-39, 2000
- C.S. Holling, Engineering resilience versus ecological resilience, pages 31-44 in P. Schulze, editor. Engineering within ecological constraints. National Academy Press, Washington, D.C., USA, 1996
- E. Hollnagel, D.D. Woods and N. Leveson (Eds.), Resilience engineering: Concepts and precepts, Aldershot, UK: Ashgate, 2006
- S.L. Pimm, The Balance of Nature?, Chicago: Univ. Chicago Press 434 pp., 1991
- C.L. Redman and A.P. Kinzig, Resilience of past landscapes: resilience theory, society, and the longue durée, Conservation Ecology 7(1): 14, 2003, URL: http://www.consecol.org/vol7/iss1/art14
- B. Walker, C.S. Holling, S.R. Carpenter and A. Kinzig, Resilience, adaptability and transformability in social-ecological systems, Ecology and Society 9 (2): 5, 2004, URL: http://www.ecologyandsociety.org/vol9/iss2/art5/
- Oxford Dictionaries, URL: http://oxforddictionaries.com/
- EUROCONTROL, A white paper on Resilience Engineering for ATM, 2009, URL: http://www.eurocontrol.int
- Olga Gluchshenko, Peter Foerster “Performance based approach to investigate resilience and robustness of an ATM System”, ATM Seminar 2013, June 10-13, 2013 in Chicago, IL, USA, URL:http://www.atmseminar.org/seminarContent/seminar10/papers/277-Gluchshenko_0127130117-Final-Paper-4-8-13.pdf
- SESAR JU, Concept Story Board, 2nd June 2009
- ICAO, Manual on Global Performance of the Air Navigation System, Doc 9883, 2009, URL: http://portal.aerocivil.gov.co/portal/pls/portal/!PORTAL.wwpob_page.show?_docname=8053536.PDF
- O. Gluchshenko, Definitions of Disturbance, Resilience and Robustness in ATM Context, DLR Report IB 112-2012/28, release 0.07, 2012, URL: http://elib.dlr.de/79571/1/IB-112-2012-28_web_Gluchshenko_0.07.pdf
- O. Gluchshenko, Concept of Resilience and Robustness in ATM Context, unpublished
- E.J. Rykiel, Towards a definition of ecological disturbance, Australian Journal of Ecology, Volume 10, Issue 3, pages 361 - 365, September 1985