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UK Civil Aviation Regulations

These are published by the CAA on our UK Regulations pages. EU Regulations and EASA Access Guides published by EASA no longer apply in the UK. Our website and publications are being reviewed to update all references. Any references to EU law and EASA Access guides should be disregarded and where applicable the equivalent UK versions referred to instead.

The origins of bowtie are to be found in a simplified fusion of fault and event tree methodologies.

In the 90’s the oil and gas industry founded and developed the practical application of bowtie as a tool to facilitate a better understanding of how risks were being overseen and managed. The benefits of the methodology have since been recognised in numerous other industries including defence, medical, financial and the aviation industry.

A barrier-based approach to risk

The aviation community are mostly familiar with Prof James Reason’s model, referred to as ‘Swiss cheese’ and the bowtie is a barrier-based structure illustrating this approach. This method is also referred to in ICAO’s Safety Management Manual (SMM) document referencing defensive barriers in accident causation with ICAO Annex 19 referring to understanding and appreciating safety risk controls

Bowtie achieves this by not only identifying the controls (or barriers) in place but also looking at control failure mechanisms (as escalation factors) and in turn how these are managed (as escalation factor controls). Based on these considerations, insights are gained into the organisation’s risk mitigation strategies and therefore into the appropriate management of safety resources.

The main strength of the barrier approach is as a qualitative tool, which is a practical solution for the challenges of risk assessment in the dynamic operating environments of the aviation industry.

The barrier approach of the bowtie, while most often used as a proactive risk assessment tool, may also be of benefit for the reactive classification of safety events as evidenced by the development of the Aviation Risk Management Solutions (ARMS) Safety Issue Risk Assessment (SIRA) tool.