Frida Eiman Kajsa Jönsson
Abstract
LFV Teknik is an airport consultancy group within the Swedish Civil Aviation Administration. They make risk assessments in connection to changes of the airport routines, when new technological equipment is to be installed or when already existing equipment are to be rebuilt. The risks are assessed in a risk matrix, but today there are no standardized outlines how to perform the assessment. This results in different assessments depending on which person who made it.
Background
This thesis is a master thesis at the programme Risk Management and Safety Engineering at Lund University Faculty of Engineering. The project was carried out in cooperation with LFV Teknik with the aim to analyse common airport associated aviation risks.
The aviation industry is associated with many risks in the every day activities. On account of this all the Swedish airports must, in a form of safety cases, prove to the Swedish Civil Aviation Authority that enlarging and reconstructions that are planned to be done on buildings do not pose a risk to flight safety. Within the Swedish Civil Aviation Administration there is a particular division, LFV Teknik, that among other things works with performing safety cases. These contain a systematic survey of potential risks and analysis associated with the new system that is supposed to be introduced at the airport. After performed analysis, the risks are assessed in a risk matrix concerning the parameters probability and consequence. The axis of consequence is divided into four steps from minor to catastrophic occurrences. The axis of probability has one quantitative and one qualitative definition, and is divided into five steps from extremely improbable to frequent. Depending on where in the risk matrix the risk ends up it will be categorized into
acceptable, unacceptable or to be reviewed (LFV Teknik, 2004).
LFV Teknik is dealing with a number of risks, named typical risks, which frequently recurs in the safety cases. These could for example be obstacles on or near the runway, collision between two aeroplanes, powerful braking of an aeroplane or light system failure during take-off or landing.
In the present situation there are no standardized outlines for how to perform the risk assessment. Because of this the assessments may differ from each other depending on the person who has done the assessment. People have different perception of risk that may influence assumptions and conclusions in the work of safety case. The perception of risk means that persons assess risks different because of earlier experiences, knowledge about the risk, the range of the consequences etc. The assessor also chooses how many actions in the chain of events that are to be taken into account, both with regards to possible consequences and to underlying conditions. This leads to that one and the same risk may be assessed differently from case to case, and consequently uniform assessment does not appear.
Purpose
This thesis aims to analyse the risk matrix and at forming the basis of a more objective risk assessment of 18 type risks by establish probability and possible consequences of these.
Method and delimitations
Interviews with twelve flight safety experts (pilots, safety coordinators and analysts) were made in the aim of finding possible consequences and probabilities for 18 typical risks plus belonging risks. The same questions and scenarios were used in each interview, so that the results could be put together and compared.
Risks can bring both positive and negative consequences. To increase the aviation safety it’s nevertheless the negative consequences that are most important. Because of this only the negative effects has been treated in the interviews and in this thesis.
Results
The results of the interviews show that undesired occurrences, as for example disruption of light systems, which occurs before decision height do not pose a threat for flight safety. In flight simulators pilots train their ability to handle these situations and they mean that they do have time to break off approach and to do a go around. The majority of the interviewed persons also mean that the passengers wouldn’t even notice that something had gone wrong during the landing and that a go around was done.
Undesired occurrences that occur after decision height do on the other hand involve increased risk.
The results show that the consequences of undesired occurrences though are rare. Often the probabilities for catastrophic or major occurrences are very small. This is related to the fact that take-off and landing often are made automatically and therefore are not affected of total light failure.
Nevertheless, the research also shows that the airport and the aeroplanes have got a number of safety barriers. These, for example redundant systems, make the risk often very small or non-existent. In case of a decline of more than one safety barrier at the same time, the probability is higher for serious consequences.
The most critical light system to go out is the runway centre line lights and the runway edge lights. During take-off the runway centre line lights give the pilot information about the depth of the runway and also help the pilot to keep the aeroplane centred on the runway. During landing the runway edge lights show how the aeroplane is situated in relation to the runway.
Discussion
The probabilities for the consequences were often very small, wherefore uncertainties of the results occur. For the human person it’s often hard – or in some cases even impossible - to assess small probabilities (Riskkollegiet, 1991). The difference of 10^-6 and 10^-7 are one example when it’s difficult to tell the difference but important to the final results. Even tough the results sometimes are spread, one can see if the risk would result in catastrophic or minor accidents and also give a hint of how probable this is.
Because of the uncertainty of the probabilities LFV Teknik is recommended to complement the results with a consensus group. The purpose of this group is to analyse the results from this thesis
and to find answers from the interviews that are less reliable. An answer that sticks out among the others may depend on if the person who answered misunderstood the question, didn’t have the right experience and knowledge about the risk or his/her perception of risk.
The definitions of the consequence axis in the risk matrix contain quite a lot of indistinctness.
Among other things synonymous words are used in the different classes of consequences that allow free scope for the assessor to make his own interpretations. Also, only possible to assess risks associated with safety and health, despite that LFV Teknik works according to the environmental management system ISO 14001. Because of insufficient definitions the risk matrix should be completed with numbers and example of possible consequences for each class on the consequence axis. This would simplify the assessment and the differences between the assessments would be reduced.
Nevertheless this is going to be developed in the organisation of the Swedish Civil Aviation Authority and a new improved version is going to reach the organisation within two years.
Conclusions
A short summary of the conclusions of the thesis:
An undesired occurrence, which occurs before decision height, does not pose a threat for flight safety.
An undesired occurrence, which occurs after decision height, involves increased risk. The probabilities of catastrophic occurrences are nevertheless often very low.
The most critical light systems to go out is the runway centre line and edge lights.
LFV Teknik should compose a consensus group to analyse the results of this thesis because of the uncertainties of the low probabilities.
References
LFV Teknik, H., 2004, Handbok i säker- hetsbevisning för LFV Teknik, LFV Teknik, Norrköping.
Evaluation of airport associated aviation risks
Riskkollegiet, 1991, Att jämföra risker, Skrift nr 1, Riskkollegiets Skriftserie, Stockholm.
Safety Culture in Extensive Projects