Special Cause Variations

 Special Cause Variations

By OffRoadPilots

Special cause variation, also known as assignable cause variation, refers to the

variation in a process or system that can be attributed to specific, identifiable

factors or events that are not part of the inherent, normal variability of the

process. In other words, special cause variation represents deviations from the

expected or standard performance of a process that can be traced back to specific,

often unusual, and non-random factors.

Key characteristics of special cause variation include:

Identifiability: Special causes

are specific and identifiable.

You can pinpoint the exact

reason or event that caused

the variation in the process.

Unpredictability: Special

cause variation is typically

unpredictable and sporadic.

It is not part of the regular

pattern of variation that a

process exhibits.

Infrequent Occurrence:

Special causes occur

infrequently and are often

considered exceptions or

anomalies in the process.

Isolation: When special cause

variation is detected, the goal is to identify and isolate the cause, so it can be addressed and eliminated to improve process stability and consistency.

To better understand special cause variation, it is often contrasted with common

cause variation, which represents the inherent variability in a process that is

typically present even when the process is operating under stable conditions.

Common cause variation is a result of the natural variation within a process and is

expected to occur over time.

In various fields such as quality control, manufacturing, and process improvement,

distinguishing between special cause and common cause variation is essential for

effectively managing and improving processes. Statistical tools and process control

techniques, such as control charts, are often used to detect and address special

cause variation and maintain process stability and consistency.

A root cause analysis is required after a special cause variation interrupts or

deviate a process. Root cause analysis (RCA) is a systematic process used to

identify the underlying or fundamental causes of an issue, problem, or incident. It

is a valuable problem-solving technique employed in various fields, including

engineering, healthcare, manufacturing, and business, to understand why

something went wrong and to develop effective solutions to prevent it from

happening again. RCA typically involves the following steps:

Clearly articulate the special cause variation to investigate. This step is crucial

because it sets the scope and boundaries for the analysis. It was a special cause

variation which lead to an issue, and this cause must be specific and clearly defined

in the written text of the background for the root cause analysis.

Collect data and information related to the problem. This can include incident

reports, documentation, interviews with involved parties, and any relevant

records.

Determine the immediate or proximate causes of the problem. These are the

events or factors that directly led to the issue.

Dig deeper to find the root or underlying causes of the problem. These are the

systemic or foundational factors that allowed the immediate causes to occur.

Common tools used for this step include the "5 Whys" technique, fault tree

analysis, fishbone diagrams (Ishikawa diagrams), or process flowcharts.Not all root causes are of equal importance. Prioritize them based on their impact,

frequency, and the feasibility of addressing them. This helps in focusing resources

on the most critical issues.

Once you have identified the root causes, devise corrective actions or solutions to

address them. These actions should be specific, actionable, and targeted at

preventing the recurrence of the problem.

Implement the corrective actions and continuously monitor their effectiveness.

Verify that the problem has been resolved and that there are no unintended

consequences.

Keep a record of the entire

RCA process, including the

identified causes and

corrective actions taken. This

documentation is valuable for

future reference and for

sharing lessons learned.

Root cause analysis is a

proactive approach to

problem-solving that aims to

address the source of issues

rather than just treating

symptoms. It helps SMS enterprises improve their processes, enhance product and

service quality, and is designed to prevent costly and potentially dangerous incidents from happening again. After root cause analysis and the corrective action is implemented, new special cause variations may adapt to processes, and deviate from expected outcome.

Special cause variations are independently adaptable to the process. A corrective

Special cause variation is the square root of PI and is without an end or beginning.action plan is designed to correct a known special cause variation, but a new

special cause variation will sooner or later integrate itself in a process, interrupt

the process, and cause a different outcome. The new process output may be

advantageous to the outcome or destructive to the outcome. A special cause

variation is neutral without preferences to the outcome.

A corrective action plan (CAP) follow-up is a crucial step in the process of

addressing and rectifying issues or problems within an SMS enterprise. It involves

monitoring and evaluating the progress of the corrective actions that were

implemented in response to identified problems or deficiencies. The purpose of

the follow-up is monitoring to assess if actions taken are effective in resolving the

issues, that the special cause variation was eliminated, and to analyse if new

special cause variations, or drift, are introduced to the process. A CAP

implemented does not prevent future special cause variations to be introduced.

Here are the key steps involved in a corrective action plan follow-up.

Review the Corrective Action Plan: Begin by revisiting the original corrective action

plan to understand the specific actions that were proposed and agreed upon. This

should include a clear description of the problem, the root causes, and the steps to

address them.

Establish a Follow-Up Schedule: Determine a follow-up schedule that outlines

when and how often progress will be assessed. The frequency of follow-ups may

vary depending on the nature and urgency of the problem but typically includes

regular check-ins.

Assign Responsibility: Clearly define who is responsible for monitoring and

overseeing the corrective actions. Assign roles and responsibilities to ensure

accountability. This may involve team members, managers, or specialized

individuals depending on the complexity of the issue.

Data Collection and Analysis: Gather relevant data and information to assess

progress. This may involve collecting metrics, conducting surveys, reviewingincident reports, or other forms of data collection that are pertinent to the issue at

hand.

Evaluate Progress: Compare the actual progress made against the objectives and

goals outlined in the corrective action plan. Determine if the actions taken have

had the desired impact and are effectively addressing the root causes of the

problem.

Adjustments and Revisions: If progress is not as expected or if new special cause

variations arise, be prepared to make adjustments to the corrective action plan.

This may involve revising the plan, changing strategies, or allocating additional

resources.

Communication: Keep all relevant stakeholders informed about the progress of the

corrective action plan. Effective communication is crucial to ensure everyone

involved is aware of the status and any changes that may occur.

Documentation: Maintain detailed records of the follow-up process, including

meeting minutes, data collected, and any changes made to the plan.

Documentation is essential for transparency and accountability.

Closure: Once the corrective actions have successfully addressed the special cause

variation, and it is unlikely to recur, formally close the corrective action plan. This

involves obtaining final approvals and ensuring that the issue is resolved to

compliance with the SMS policy and expected outcomes.

Continuous Improvement: Use the insights gained from the corrective action

process to improve organizational processes and prevent the same issue from

occurring in the future. Encourage a just culture of continuous improvement. The

difference between continuous and continual improvements is that continuous

improvement is the change, or repair to current process for the purpose of

maintaining a known process, while continual improvement is to abandon the

current process an implement a new process. Example of a continuousimprovement process is to change from verbal format recording to written format

reporting. Example of a continual improvement process is to change from paper

format process to a web-based electronic format such as SiteDocs.

(www.sitedocs.com – offroadpilots@gmail.com)

Corrective action plan follow-

up is an iterative process that

may require multiple cycles of

assessment and adjustment

until the desired outcomes

are achieved. It is a vital

component of quality

management and risk

mitigation in SMS enterprise

organizations.

Special cause variation occurs

in processes due to specific, identifiable factors or events that are not part of the

inherent, normal variability of the process. These factors or events can be categorized into various reasons.

External Factors: Special causes can be introduced by external influences that are

beyond the control of the process. For example, changes in environmental

conditions, equipment malfunction, power supplies, external supplier issues,

human factors, organizational factors, supervision factors and environmental

factors can lead to special cause variation.

Human Errors: Mistakes made by individuals involved in the process can introduce

special cause variation. This includes errors in data entry, measurement, or

operation of machinery.

NOTE: Human error is a sub-category of Human Factors, which are integrated, or

built into a system for a desired process output. Human errors may not necessarily

cause an accident, it could also improve a process reliability.

Process Changes: Any deliberate or unintentional changes made to the process can

introduce special cause variation. This includes adjustments to process

parameters, changes in raw materials, or modifications to equipment. A complete

system analysis for planned process changes is needed, while unintentional

process changes are drift, or introduction of other acceptable work practices.

Equipment Failures: Mechanical or technical failures of equipment used in the

process can lead to special cause variation. For example, a machine breakdown or

a sensor malfunction can disrupt the process.

Outliers: Occasionally, extreme or rare events can occur that disrupt the process.

These events might include accidents at arriving or departing airport, extreme

weather conditions, or other unforeseen circumstances.

Variability in Input: Variability in the inputs or materials used in a process can result

in special cause variation. For instance, if the quality of raw materials varies

significantly, it can lead to variations in the output. New personnel hired are

special cause variation, which could lead to unplanned outputs.

Inadequate Training: Insufficient training or skill level of personnel involved in the

process can lead to errors and special cause variation. Training serves two

purposes. One is to detect drift in operational control by flight crew or mechanics,

the second is to detect organizational drift. A potential issue with assigning training

tasks to a person who does not hold a position to train as a regular trainer is that

there is often not enough time to do so adequately and introduce a special cause

variation. In preparation for training an instructor needs to do research, design a

training plan, scheduling g, and develop target specific training goals to conform to

an SMS enterprise’s safety policy and training objectives.

There are SMS enterprises, both large and small, that believe training is busy-time, or waste of time since their personnel was already trained. In addition, refresher training that

is not a part of a regulatory requirement are discouraged and not allowed during

regular working hours. When an SMS enterprise, or a person in a leadershipposition does not seek or take advantage of all training opportunities available to

their personnel, their skills become stale.

Failure of their Daily Quality

Control Process: Problems in

quality control mechanisms,

such as ineffective inspection

processes or sampling

methods, can allow defects or

deviations to enter the

process and cause special

cause variation. A proven

system to maintain daily

quality control as a

prerequisite for the triennial

quality assurance audit is the Daily Rundown Max system, which is supplied by an

aviation college for airport operators. The Daily Rundown system takes airport

operations from the level of an airport maintainer, to the level airport manager

and manual design and maintenance, and to the accountable executive level for

regulatory compliance.

Design Flaws: Sometimes, special cause variation can be traced back to design

flaws in the process or equipment, which can lead to unexpected performance

issues. Some years ago, a flaw was discovered in compressor turbine disk by

applying non-destructive testing of the CT disk. This test was the first test after the

final production stage and after it had left the production line. The test discovered

a flaw in the material and was reported. There was no safety management system

reporting avenue at that time, just an inspection report. This material flaw was the

very first flaw in a CT disk that management new of. At some point during the

manufacturing process a special cause variation was introduced. There have been

several CT disk failures in turbine engines and Sioux City IA is the best high-profile

accident known.

It's important to note that the identification of special cause variation is a critical

step in process improvement and quality control. By identifying and addressing the

specific causes of variation, organizations can work to eliminate or mitigate these

factors to achieve more consistent and predictable processes. This, in turn, leads

to improved product or service quality and overall operational efficiency. Statistical

methods, such as control charts, hypothesis testing, and root cause analysis, are

often used to detect and address special causes in various industries and

processes.

Special cause variations are common process variations in the aviation industry.

For our own comfort and safety while flying, we like to believe that established

processes and checklists are fail-free, and when adhered to, there will be no longer

be any aircraft accidents. We also like to believe that 100% of pilots adhere to

100% of processes 100% of the time. However, here is the news, special variations

in aviation will always exist, which is one reason to run with a healthy safety

management system which includes a daily rundown quality control system.

Super Centers normally have automatic walk-in doors and walk-out doors. As long

as the automatic doors are functioning as expected, everything is fine and without

scuffles. When the walk-out door malfunction and remains open, there is a special

cause variation. This special cause variation is a causal factor for scuffles. The

special cause variation is not the root cause, but a variation interrupting the

designed process.

OffRoadPilots