Make An Effective Root Cause Analysis
Within an aviation safety management system, a root analysis should be conducted of special cause variations which caused an incident. The two types of variations are the common cause variations and special cause variations. A common cause variation exists within the system itself as an inherent risk and is to be mitigated by applying a risk analysis of a probability exposure level upon arrival at location, direction, or time. Bird migration and seasonal airframe icing are examples of common cause variations. Special cause variations do not exist within the process itself but are interruptions to a process by external forces. Birds or wildlife on the runway, or icy runway are special cause variations, since they are beyond airport certification requirements, and the airport operator is expected to maintain a bird and wildlife free runway environment and a contamination free movement area. However, for an airport operator both bird and wildlife and ice contamination are common cause variations to which they should apply an expected exposure level upon arrival of an aircraft.
The two most common root cause analysis processes are the 5-Why-s and the Fishbone. The fishbone analysis is a visual analysis, while the 5-Why-s is a matrix. Preferred method is defined in the Enterprise’s SMS manual. A root cause output, or corrective actions required, will vary with the type of analysis used and the subjectivity of the person conduction the analysis. The first step in a root cause analysis is to determine if a root cause is required and why it is required. A risk level matrix should identify when a root cause is needed. A root cause analysis should be conducted for special cause variations. However, the risk level of a special cause should be the determining factor for the analysis. For a risk matrix to be both objective and effective, it must define the immediate reaction upon notification, identify when a root cause analysis is needed and define both the risk levels when an investigation is required, and at what acceptable risk level an investigation is conducted.
When conducting a root cause analysis there are four factors to be considered. The first factor is human factors, the second is supervision factors, the third is organizational factors and the fourth is environmental factors. Environmental factors are categorized into three sub-factors, which are the climate (comfort), design (workstation) and culture (expectations). Culture is different than organizational factors in that these are expectations applied to time, location, or direction. Example: A client expect a task to be completed at a specific time at an expected location with direction of movement after the task is completed. Organizational factors are how the organizational policies are commitments to the internal organization in an enterprise and the accountable executive’s commitment.
|There is only one root cause, |
but several options for selection
|The root cause is your compass.|
A root cause analysis is to backtrack the process from the point of impact to a point where a different action may have caused a different outcome. A five columns root cause matrix should be applied to the analysis. Justifications for five columns analysis is to populate the root cause matrix with multiple scenarios questions rather than one scenario that funnels into a root cause answer. The beauty of a five-column root cause analysis is that answers from any of the column may be applied to the final root cause, and if it later is determined to be an incorrect root cause, the answers to the new root cause analysis is already populated in the matrix. When the root cause is assigned, it should be stated in one sentence only. It is easy to fall into a trap assigning the root cause to what was not done. However, since time did not stop and something was done, the root cause must be assigned to what was done prior to the occurrence. An example of an ineffective root cause would be that the pilot did not conduct a weight and balance prior to takeoff. In the old days of flying, the weight and balance of a float plane was to analyze the depth and balance of the floats. Airplanes flew without incidents for years using this method. For several years standard weights were applied to personnel and luggage. Applying the standard weight process is similar to applying the float analysis process. Aircraft flew without incidents for years applying guestimates of weight rather than actual weight. At the end of the day, the fuel burn became the tool to confirm if correct or incorrect weight was applied. That a weight and balance was not done is not the root cause. The root cause could be one or a combination of human factors, organizational factors, supervision factors or environmental factors. The next step in a root cause analysis is to analyze these factors to assign a weight score to the root cause factor.
A weight score is applied to human factors, organizational factors, supervision factors and environmental factors by asking the 5-W’s + How. Examples of considerations are shown below.