Every aviation safety management system (SMS) contains a subsystem to manage risk associated with reported safety issues and audit findings. This subsystem can be called the SMS' risk management system as this system provides the logical workflow necessary to efficiently:
Reported safety issues and audit findings enter the SMS risk management system. The risk management system provides a repeatable process to run safety issues through the organization's documented risk management processes. These processes may be manual or facilitated by the use of SMS database software.
Aviation SMS databases provide operators with repeatable workflows and tools to track and document the safety teams' risk management activities. Most aviation service providers benefit from SMS databases in that accountable executives, operational department heads and safety managers can more easily monitor organizational safety performance with the use of real-time dashboards or predefined charts and graphs.
Most commercially available SMS databases also have sophisticated modules to conduct in-depth investigations that include documentation capabilities for:
Each safety issue that is processed in the risk management system has a life cycle. Some safety concerns may require an in-depth investigation, while minor issues may not warrant a full-blown investigation. During the investigatory process, a root cause analysis may be performed by:
Root cause analysis for one aviation safety manager is not root cause analysis for another safety manager. What I'm trying to say is that there is no standard definition or process for root cause analysis in SMS guidance materials.
This lack of standardization is not a negative thing, as it gives aviation service providers the flexibility to create a process that best fits them. In anticipation of this, oversight agencies like the FAA or ICAO provide little guidance on how to conduct a root cause analysis.
It’s less important to “define” root cause analysis than to understand how you can use a method to meet root cause analysis goals. Root cause analysis is performed by adopting a method, such as:
Either of these methods will be used to:
Below, we will take a more in-depth look at three methods for root cause analysis while running safety issues through your risk management life-cycle.
Fishbone diagrams, also known as cause and effect diagrams, derive their name from the fish-like appearance of a completed diagram. Fishbone diagrams are also known as cause and effect diagrams and Ishikawa diagrams.
These diagrams have:
Filling out these diagrams simply involves looking at the safety issue from the perspective of each fin (category), and establishing the relevant factors (branches). Next, for each branch, establish the reasons (sub-branches) that the branch exists. These sub-branches are usually your root causes. See the above example picture to see what this looks like.
The benefits of using fishbone diagrams are:
The cons of fishbone diagrams are:
5-Whys analysis is the most common method used for root cause analysis. Some of the reasons this method is ubiquitous in aviation SMS risk management processes are that the process is:
Unlike some of the other methods, however
Performing 5 whys analysis is easy to do. It involves starting at your hazardous condition/risk event, and then asking “Why did this happen?” You will then establish the preceding event/reason that leads to the hazardous condition. Next, you will ask, “And why did this preceding event happen?” Once again, you will establish the next event.
You will repeat this process until you arrive at the root cause. Usually, you will ask "Why?" about 5 times, give or take a couple. You know you have arrived at the root cause when there is no real answer to “why?” In other words, when your answer is “just because,” you have arrived at the root cause.
Bowtie analysis is traditionally considered a comprehensive analysis solution, as it establishes everything from root causes to final consequences. Because bowtie analysis is so thorough, it can be time-consuming and abstruse. However, there is no reason organizations can’t use only the “left side” of the bowtie to establish a timeline of all contributing events from root causes to hazardous conditions.
Performing bowtie analysis for root causes is somewhat similar to 5 whys analysis:
Unlike the 5 whys, bowtie analysis:
However, reasons you might use 5 whys analysis instead of bowtie are:
It’s also possible to create a custom root cause analysis method that meets your organization’s specific needs. For example, you might create:
It’s not so important which method you use. What matters is how well your root cause analysis meets the goals of obtaining the root cause from your analysis.
For a similar method of analysis, see this guide to SMS Shortfall Analysis.
Last updated in July 2024.