A Fuzzy-based Site Selection Framework for Emergency Landings of Commercial Aircraft

What is it about?

It is rare for a commercial passenger aircraft to be forced to carry out an emergency landing. Nevertheless, when such an event occurs, pilots are responsible for selecting a suitable landing site and flying the aircraft towards that site for a safe landing. This study addresses the challenges associated with the selection of the best emergency landing site – in a total loss of thrust scenario – by proposing a fuzzy logic framework which mimics the reasoning and decision-making process of airline pilots. The framework consists of a number of fuzzy logic systems which are used to quantify the risk associated with each landing site (conventional or unconventional) within the remaining gliding distance of the aircraft. The landing sites are then ranked in order of risk and presented to the crew. This risk assessment is not limited to the landing sites themselves, but also accounts for risks associated with the trajectories leading to those sites. Various aspects of the fuzzy logic framework – including the fuzzy variables, fuzzy sets, membership functions and fuzzy rules – were defined with the input of experienced commercial airline pilots and are discussed in this paper. The results of a preliminary evaluation of the proposed framework demonstrate its suitability for the intended scenario.

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Photo by Erwan Hesry on Unsplash

Photo by Erwan Hesry on Unsplash

Why is it important?

Various situations can force the crew of a commercial passenger aircraft to perform an emergency landing, including: Total Loss of Thrust (TLOT), onboard fire, structural damage and hydraulic failure. The onboard automation of current passenger aircraft – such as the A320 and B737 – provides limited assistance in these situations. For instance, the Flight Management System (FMS) provides a list of nearby airports; however, it is up to the crew to identify the most suitable landing site and to fly towards it whilst avoiding hazardous weather, high terrain, and other obstacles along the way. The chances of a successful landing depend on various factors, including the ability of the crew to: react quickly and assess the post-failure performance of the aircraft; evaluate different landing options and make tradeoffs between various criteria; and fly the aircraft in a way that it can reach the selected landing site at a safe height and speed. The process leading to the selection of a landing site has to account for the influence of various factors, including: the glide performance of the aircraft; the aircraft’s altitude at the onset of the emergency situation; the prevailing weather conditions; the distance to each candidate landing site; and the physical characteristics of each landing site. Assuming that information on these factors is available and quantifiable, a computerised system that can quickly evaluate and rank potential landing sites – on the basis of risk – would be very useful and is highly desirable.

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