A Look at Aviation Risk Management Solutions: Safety Issue Risk Assessment

Written by Stuart Grimsey, Senior Consultant at Baines Simmons

ARMS SIRA: Moving from Events to Safety Issues

In my previous article, we explored how the ARMS Event Risk Classification (ERC) tool supports triaging incidents. However, triaging alone does not effectively manage risk. Once an organisation identifies a recurring pattern or hazard theme, the question becomes: how serious is this issue in context, and what level of control or mitigation is needed? Traditional Risk Management provides a framework to address this, the Aviation Risk Management Solutions (ARMS) Safety Issue Risk Assessment (SIRA) methodology approaches this from a different angle.

SIRA complements ERC by focusing on proactive assessment of known safety issues, rather than reactive classification of past events. The tool is designed to help organisations evaluate the real-world risk of hazards by considering four core elements:  

1. Frequency / probability of the Triggering Event 
2. Effectiveness of Avoidance Barriers 
3. Effectiveness of Recovery Barriers 
4. Severity of the accident outcome 
   
   

In this article we’ll look at SIRA’s outputs, the process and pros and cons of the methodology.



SIRA Outputs: Explained

Like ERC, SIRA aims to offer repeatable and defensible outputs that can inform data-driven risk-based decision-making. But the goals of the tool are subtly different. 

SIRA is designed to enable: 

1. Quantified Risk Judgement – By analysing how often a hazard could lead to an accident and how well it’s currently controlled, SIRA allows organisations to place safety issues on a risk matrix with meaningful granularity. This supports prioritisation and resourcing decisions. 
2. Barrier-Based Thinking – SIRA leans heavily on the use of BowTie or similar models. It doesn’t just ask “how likely is this to happen?” but rather “how strong are our defences at each stage?”. 
3. Structured Decision Making – By taking a four-part approach (Frequency, Avoidance, Recovery, Severity), SIRA provides a logical and transparent framework that can be challenged, audited, and improved over time. 
4. Alignment with SMS and Management of Change – The output from SIRA supports Safety Management System (SMS) processes and is especially valuable when assessing safety implications of changes to equipment, operations, or organisational structure.

SIRA Methodology: Process
The SIRA methodology consists of four interlinked stages, all of which can be mapped using the ARMS SIRA Excel Tool:

Step 1 – Define the Safety Issue 

This may sound obvious, but poorly scoped safety issues are a leading cause of weak risk assessments. SIRA requires that the issue be clearly articulated, including relevant aircraft types, operational contexts, and timeframes. For example: “Runway excursion risk during wet weather at coastal airports due to deferred rubber removal.” 

Step 2 – Estimate Hazard Frequency (F) 

How often does the hazard (e.g. rubber build-up, maintenance oversight, unstable approach) occur in your operation? Expressed per sector or relevant operational unit, this estimate is often supported by Flight Data Monitoring (FDM), audit results, or expert judgement.

Step 3 – Evaluate Barrier Effectiveness 

SIRA uses a two-layer barrier model: 

• Avoidance Barriers – How likely are existing systems to prevent the hazard from escalating into an unsafe situation? 
• Recovery Barriers – If the hazard does lead to an event, how effective are the systems in place to recover from it? 

These are scored on a logarithmic scale representing failure probability. This approach avoids vague discussions of “likelihood” and instead focuses on the actual capability of your safety controls. 

Step 4 – Determine Consequence (Severity) 

This is the most credible outcome (not the worst imaginable) if both barrier layers fail. For instance, a runway excursion in good weather might have negligible consequences, whereas one during low visibility at a challenging airport might plausibly result in major damage or injury. 

Once all four elements are assessed, the results are passed through a two-stage matrix process. A free Excel tool is available for this, and some SMS Software applications have module add-ons to do this, although it is perfectly feasible to complete manually: 

• Stage 1: Combines Frequency and Avoidance to define the event likelihood. 
• Stage 2: Combines event likelihood and Severity, adjusted by Recovery barrier failure rate, to define risk tolerance level.
   

This outcome falls into one of two zones: Tolerable levels of risk (Accept, Monitor, Secure) or Unacceptable levels of risk (Improve, Stop).

The ARMS Methodology for Operational Risk Assessment in Aviation Organisations v4.1 (2010, available to download from EASA or Skybrary and the manual for ARMS ERC and SIRA) contains several worked examples covering ERC and SIRA.