SMS Quick Takes: How to Assess Safety Risk
How to Assess Safety Risk
In the first two posts of this series, we laid the groundwork for effective Safety Risk Management (SRM) by explaining how to describe systems and operating environments and how to perform hazard identification using Federal Aviation Administration (FAA) (see FAA Advisory Circular 120–92D, pp. 2–7, paragraph 2.6.3) and International Civil Aviation Organization (ICAO) (see ICAO Doc 9859 – Safety Management Manual (SMM), p.(vii), Hazard) definitions. Now we’ll discuss what you’ll do next: risk assessment.
This is the next SRM step under part 5 once hazards have been clearly identified and where organizations evaluate how serious a hazard could be and how likely it is to lead to an aircraft incident or accident, before deciding whether additional risk controls are needed.
Risk assessment is often misunderstood as a mathematical exercise. In reality, it’s a structured decision-making process designed to support sound safety judgments using a consistent, repeatable approach.
✈️ What Does “Assessing Risk” Mean in SRM?
Under part 5 and FAA Advisory Circular (AC) 120–92D, assessing safety risk means evaluating two dimensions for each identified hazard:
- Severity: How serious could the potential outcome be?
- Likelihood: How probable is it that the hazard could lead to an incident or accident?
Together, these elements help organizations understand risk exposure and prioritize safety actions appropriately. Importantly, risk assessment is not about predicting the future with precision—it’s about making informed decisions using available data, operational knowledge, and professional judgment.
✈️ Severity: How Bad Could It Be?
Severity reflects the potential consequences if a hazard leads to an aircraft incident or accident.
Under 14 CFR part 5 and FAA Advisory Circular 120-92D, severity categories are not universal. The organization should define them to reflect its systems, aircraft, and operating environment. Commonly used categories often resemble the following generic examples:
Does not significantly reduce system safety or operational capability (this is inconvenient, but manageable).
Example: A minor airframe discrepancy found during preflight and corrected using standard procedures, resulting only in a brief delay.
Reduces safety margins or increases workload to a noticeable degree (this meaningfully degrades operations).
Example: A system malfunction that requires a go-around or diversion, increasing crew workload and reducing margins, but remaining manageable.
Severely reduces safety margins or significantly increases workload, with potential for serious injury (this puts safety at real risk).
Example: A combination of degraded weather and system anomalies during a critical phase of flight that nearly results in loss of control.
Results in multiple fatalities and/or loss of the aircraft (this is unrecoverable).
Example: A loss-of-control accident with no opportunity for recovery.
- Focus on aviation safety outcomes, not business inconvenience.
- Consider effects on people, aircraft, and operational control.
- Apply severity categories consistently across similar hazards.
For example:
- A hazard involving runway contamination may have high severity due to loss of control potential.
- A hazard involving incorrect documentation for a non-critical component, identified and corrected before flight, may have lower severity.
✈️ Likelihood: How Often Could It Happen?
Likelihood describes how often a hazard could reasonably be expected to result in an aircraft incident or accident, given current conditions and controls.
The organization should define likelihood categories to reflect its operational environment. Commonly used categories often resemble the following generic examples:
So unlikely it can be assumed the event may never be experienced (we don’t realistically expect this to happen).
Unlikely, but possible under specific or unusual conditions (this could happen, but not very often).
Could occur sometimes during normal operations (this could happen from time to time).
Expected to occur more frequently than not if exposure continues (we expect this to happen again).
Expected to occur regularly (this happens a lot).
Unlike severity, likelihood assessments can be informed by data and experience, including safety reports, audits, operational exposure, and historical events — recognizing that perfect data is rarely available.
- Base likelihood on realistic operating conditions.
- Consider exposure (how often the activity occurs).
- Account for existing controls already in place.
- Avoid pure “gut feel” without operational context.
For example:
- A hazard tied to daily flight operations will generally have a higher likelihood than one associated with a rare maintenance activity.
- A hazard occurring regularly during winter operations will often rate higher than one that only appears under rare or one-off conditions.
✈️ Why Risk Assessment is Often Challenging
Organizations frequently struggle with risk assessment for reasons akin to those of hazard identification:
- Over- or under-estimating likelihood because of limited data.
- Treating severity and likelihood as absolute rather than relative.
- Applying inconsistent criteria across departments.
- Debating numbers instead of discussing risk drivers.
- Letting perceived business pressure influence ratings.
FAA and ICAO guidance emphasize that consistency matters more than precision. A simple, repeatable approach applied uniformly across hazards is far more effective than a complex system used inconsistently.
✈️ Using a Risk Matrix
A risk matrix is the most common tool used to combine severity and likelihood into a single risk classification.
| Likelihood \ Severity | Catastrophic | Hazardous | Major | Minor |
|---|---|---|---|---|
| Frequent | High | High | High | Medium |
| Probable | High | High | Medium | Medium |
| Occasional | High | Medium | Medium | Low |
| Remote | Medium | Medium | Low | Low |
| Improbable | Low | Low | Low | Low |
Illustrative example of a safety risk matrix. Operators should tailor severity, likelihood, and risk acceptance criteria to reflect their systems, operating environment, and documented SMS procedures, consistent with 14 CFR Part 5 and FAA AC 120-92D.
Risk matrices typically:
- Display severity on one axis and likelihood on the other
- Use color-coded zones (for example, green, yellow, red)
- Help determine whether a risk is acceptable or requires further control, based on risk assessment criteria
A risk matrix does not replace judgment. It does support consistent decision-making. Used correctly, it helps organizations:
Compare risks across different systems or activities; prioritize safety actions; document why a risk was accepted or mitigated.
Mask important assumptions; create false precision; become a “check the box” exercise.
✈️ Assessing Risk Before and After Controls
Risk assessment under part 5 is typically performed twice.
- Initial (or inherent) risk: This reflects the risk before additional controls are applied.
- Residual risk: This reflects the risk after existing or new controls are in place.
This distinction is critical: many hazards may initially score as unacceptable but become acceptable once effective controls are applied and verified.
Risk acceptance decisions should be made using criteria established by the organization and documented within its SMS.
✈️ Avoiding Common Pitfalls in Risk Assessment
- Adjusting severity or likelihood to “fit” a desired outcome
- Using controls to justify a low initial risk
- Ignoring uncertainty or assumptions
- Applying different standards to similar hazards
- Treating the matrix as the decision, rather than a tool
A disciplined SRM process separates analysis from decision-making. The analysis informs leadership; it does not predetermine the answer.
✈️ Risk Assessment Applies Across Aviation Sectors
Whether your organization operates aircraft, maintains them, designs or modifies them, or manufactures parts or assemblies, the principles of severity, likelihood, and risk matrices apply the same way: the specifics differ, but the structure does not.
Do you have questions or concerns about SMS? Share them with us!
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