Kapitel 6.2 Safety Assessment

Abstract

All efforts addressing the safety of flight operations with regard to wake vortex encounter (e.g. wake warning systems) or aiming at increasing the capacity of the air transport system by adjusting wake turbulence separations (e.g. new separation schemes) ultimately aim at reducing the risk of severe wake encounters or must assure that the level of risk is not increased. It is the task of dedicated safety assessments to validate that this risk is either reduced or kept at current levels. Those risk-based safety assessments that consider the possibility of unintentional wake encounter must determine the probability (i.e. frequency) of wake vortex encounters and their associated severity level. Severity assessments concern the determination of the severity of a specified wake vortex encounter. Within such assessments severity criteria correlate objective, measurable quantities with severity descriptions of more general nature and stakeholder-wide understanding. Safety assessments may differ in depth. The most detailed assessments include models of air traffic, weather, wake vortex transport and decay as well as dynamic wake encounter simulations to determine frequency and severity of wake encounters on a statistical basis. Experience shows that a common definition of applicable severity criteria is especially difficult to achieve. This difficulty is due to the fact that many different stakeholders are directly concerned (basically answering the question: “which wake encounter is acceptable?”) but that they have different perspectives, experiences and requirements. While an airline might already be concerned about the number of encounters affecting passenger comfort, a regulator is more likely to be concerned only about encounters leading to incidents.