As the range of operations and participants in aviation increases, the challenge of effective risk management across the aviation system will grow. How can we successfully manage the risks associated with these new aviation entrants, particularly the growing variety of drones/Unmanned Aircraft Systems (UAS) operations?
In this latest blog in our ‘drone integration’ series, we look at UAS operations from a safety perspective using an enhanced bowtie modelling approach as part of a new approach to safety assessment. We start in the UK, looking at the safety analysis of the future aviation system (introduced by Richard Derrett-Smith in a previous blog), and then draw conclusions from recent work undertaken for an ANSP looking at incorporating first-stage UAS Traffic Management (UTM) services into its existing risk models.
Safety analysis of the future aviation system.
The impact of new aircraft, new operators and new operating models will challenge our understanding of aviation risk and poses significant questions on how best to manage risk in the future. For example:
- A typical drone mission will probably use a hybrid navigation system, maybe even including machine learning algorithms in the background, so its performance is dependent on a collection of systems not just one.
- The UTM system will incorporate more inputs than an ATM system, at a faster rate, on a larger scale, and integrate with ATM. This will stretch the mental modelling abilities of ATCOs.
- The number of interfaces and interactions in the overall aviation system will increase, this means boundary assumptions (which are critical to most safety cases/standards/certifications) are harder to define, and existing ones likely to be invalidated).
There is no overarching consolidated record of aviation risk (in the UK) and no single risk baseline from which to make risk informed judgements about the impact of changes to the aviation system. Aviation system changes at a local level can be managed, e.g. a change in runway usage at an airport, a change to an Air Traffic Control (ATC) system at a specific Air Traffic Service Unit (ATSU), or a change in aircraft systems, as the number of interactions are limited and can be understood. But this approach does not scale effectively when you are introducing thousands of new aircraft of many different types, operating in uncontrolled airspace, and where the existing surveillance and navigation technology will not function to the required level of accuracy to ensure safe operations for all airspace users.
Added to this, there are potentially tens or hundreds of organisations entering the aviation industry with no/limited corporate history in aviation and the associated standards and culture that drive exemplary safety performance.
Today’s aviation safety case is based primarily on the lessons learned from incidents and accidents. It uses traditional safety methods to explore ways of identifying problems and developing mitigations to address them. With an expansion of aviation operations comes a demand for parallel improvements in safety, keeping the number of accidents as low as has been achieved today, and the risk as low as reasonably practicable. This means a different approach to assessing aviation safety is needed.
The UK’s Future Flight Initial Safety Framework includes safety analysis that uses a new approach to assessing total future aviation safety. The safety analysis is based on understanding risk by looking at the different stakeholder interactions within the future aviation system, not just future aircraft and associated technologies, but also the operators, airspace environment, ground infrastructure, control systems or operational system lifecycle.
Let’s take a closer look at the initial steps in that analysis.
Step 1 – Understand the risk picture.
Safety has always been the highest priority for the aviation industry and aviation is rightfully considered one of the safest modes of transport. To understand how we deliver high levels of safety performance, we can map the numerous stakeholders, with interactions occurring between many of them and try to understand what the key activities are, the hazards and controls currently in place, and why they are successful. Then we can assess the impact of new entrants on the system, by looking at how the interfaces, interactions, hazards and controls change. The bowtie modelling concept is helpful for defining the current aviation system and visualising it in an understandable way. It depicts risk, providing an opportunity to identify and assess the key controls either in place or lacking between a Threat and Consequences.
In our work for Future Flight, we used the ‘’Significant Seven’’ bowties developed by the UK CAA as a credible basis for the current aviation system. These are however limited to CAT aircraft operations and therefore extending this to encompass all airspace users is a key priority.