In this week’s article we will cover the topic of another very popular methodology in aviation Safety called “Bow-Tie” and how to use such methodology.
WHAT IS BOW-TIE METHOD?
The Bowtie methodology is a risk assessment tool that can be used to analyze and demonstrate causal relationships in high risk scenarios. Bow-Tie popularity lays in the fact that it is primary visual tool which helps Safety Managers to have a clear picture of relationships between threats, hazards, top events and consequences. Another good explanation written by the Skybrary: A Diagrammatic illustration of the hazard, the undesirable event, the trigger events/threats and potential outcomes, and the risk controls put in place to minimise the risk.
WHY IT HAS THE NAME BOW-TIE?
Due to its resemblance to a clothing bow-tie, this particular tool or methodology derived its name from that piece of clothing as it depicts the wings on each side and central point just like the Bow-Tie.
The resemblance of Bow-Tie
WHAT IS THE PURPOSE OF BOW-TIE?
Bow-Tie serves as an ideal tool to demonstrate and learn about the relationships in high risk scenarios. Furthermore, it has a clear benefit to increase awareness and understanding of the safety risk. Airlines in particular are keen to use such tool in their risk management as it gives a visual feedback and simplifies the process of identification of critical risk controls or barriers which are put in place. Monitoring such barriers, safety managers can easily assess their effectiveness. Finally, its such a simple tool that it can be used to showcase expenses and potential costs to the management.
HOW TO USE BOW-TIE?
Bow-Tie is very simple to understand. You can draw such diagram or, what we recommend, to use any risk assessment digital tool that supports Bow-Tie diagrams (our software ICARUS has a specialized module for creating Bow-Tie diagrams).
The Bow-Tie consists of different elements that build up the safety risk picture. The safety risk picture revolves around the hazard (something in, around or part of an organisation or activity which has the potential to cause damage or harm) and the top event (the release or loss of control over a hazard known as the undesired system state).
The steps to create Bow-Tie are the following:
- Step 1: Define the top event in which the safety control has been lost (for example, bird strike on landing)
- Step 2: Define the main hazard or undesired system state that can contribute to such top event which is being analyzed (for example: birds flying near the airport)
- Step 3: Define the threats that can cause the top event (for example: birds migration, marsh near the airport etc.)
- Step 4: Define the consequences that would occur if the top event is triggered (for example: engine fire, windscreen destroyed etc.)
- Step 5: Define the defenses or critical risk controls between the threats and the top event (for example for birds flying near the airport we can put a barrier establish airport wildlife management system) – its important that each threat has at least one barrier connected to it
- Step 6: Define the barriers or critical risk controls between the top event and the consequences (for example, for the consequence engine fire, our barriers could be enhance pilot training, develop emergency procedures etc.
- Step 7: Consistently monitor and assess the effectiveness of your defenses and barriers
Also, the Bow-Tie consists of an additional element – Escalation factors. Safety barriers are not 100% effective, as well as having inherent and temporary weaknesses. In Bowtie, the conditions influencing the effectiveness are called escalation factors, degradation factors or barrier decay mechanisms which will not be explored further in this article.
Full Bow-Tie diagram with all elements
ICARUS AND BOW-TIE?
ICARUS software has successfully integrated Bow-Tie methodology in aviation. Now, ICARUS customers can develop their own high risk scenarios, connect Bow-Tie elements and monitor the effectiveness of its barriers. The Bow-Tie module is integrated into Risk Management module, therefore possible to connect with other information in the software.
Example of simple Bow-Tie diagram in ICARUS software
