The Dirty Dozen

A large number of maintenance-related aviation accidents and incidents occurred in the late 1980s and early 1990s. Then, Transport of Canada identified twelve human factors that degrade a person’s ability to perform tasks effectively and safely, which could lead to errors during aircraft maintenance.

The Dirty Dozen list of human factors has raised awareness of how humans can contribute to accidents and incidents. The concept was intended to focus on reducing and capturing human error.

These twelve factors are known as the “dirty dozen“. It was eventually adopted by the aviation industry as a simple means to discuss human error in maintenance. It is important to know the dirty dozen, how to recognize their symptoms, and most importantly how to avoid or learn from the errors caused by the dirty dozen.

Avoid the Dirty Dozen – according to the FAA, about 80 percent of aviation maintenance mistakes involve human factors, and if these mistakes are not detected, this would lead to accidents. There are 12 common causes of human factor errors. Let’s understand one by one.

12 human factors for aircraft maintenance proficiency

The Dirty Dozen of Human Factors are listed below –

1. Lack of Communication

Lack of communication is a failure to transmit, receive, or provide enough information to complete a task. Lack of communication is a key human factor that can result in incorrect, or faulty maintenance. Never assume that the work has been completed.

In verbal communication, only 30% of information is received and understood by either side in a conversation. Others usually remember the first and last part of what you say.

Maintenance Engineers/Technicians must communicate with one another and explain what work has and has not been completed when changing shifts.

How to improve communication

  • Say the most important things in the beginning and repeat them at the end.
  • Use checklists.

2. Complacency

Overconfidence leads to complacency. When maintenance personnel gain experience from repeated tasks, a feeling of self-satisfaction and false confidence arises. Repeating tasks such as inspections can be ignored or skipped because maintenance personnel has performed the task several times without ever finding fault. The misconception can be made that inspection of the item is not important. However, even if rare, a fault may exist.

He or she must be mentally engaged in doing the work. All inspection items should be treated with equal importance. It must never be assumed that an item is acceptable when it has not been inspected. An engineer/technician should never sign for any work that has not been performed by him.

Avoid the tendency to see what you expect to see

  • Expect to find errors.
  • Don’t sign it if you didn’t do it.
  • Use checklists.
  • Learn from the mistakes of others.
  • Always double check your work.

3. Lack of Knowledge

Lack of knowledge means a shortage of training, information, and/or ability to perform successfully.

Lack of knowledge while performing maintenance on aircraft can result in a faulty repair which can have catastrophic consequences.

Maintenance personnel must be sure to use the latest applicable maintenance data and follow each step of the procedure as outlined. They must understand the differences that exist in design and maintenance procedures on different aircraft. For this, they have to get training on different types of aircraft.

When in doubt, a technician/engineer with experience on the aircraft should be consulted. It is always better to delay the maintenance process than to do it incorrectly and cause an accident.

Don’t guess, know

  • Use current manuals.
  • Ask when you don’t know.
  • Participate in training.

4. Distractions

Distraction is anything that draws your attention away from the task at hand. They are the number one cause of forgetting things, including what has or has not been done during the maintenance procedures. Distractions can be mental or physical in nature.

Distraction occurs because our mind works much faster than our hands and we are actually always thinking ahead. It depends on personality, physical circumstances, and the environment.

While performing maintenance on an aircraft, distraction may disrupt the procedure and when work resumes, it is possible that the technician skips over a detail that needs attention.

Get back in the groove after a distraction

  • Use checklists.
  • Go back 3 steps when restarting the work.
  • Only fix parts that you are trained to fix.
  • Ensure that the maintenance manual you are using is up to date.
  • If you do not know how to fix something, ask for help from someone who does.

5. Lack of Teamwork

Lack of teamwork is a failure to work together to accomplish a shared goal. Teamwork involves everyone understanding and agreeing on actions to be taken.

Personality differences in the workplace must be left outside the workplace, and organizations should emphasize that a lack of teamwork can ultimately affect aviation safety.

Build solid teamwork

  • Discuss how a task should be done.
  • Make sure everyone understands and agrees.
  • Trust your teammates.
  • Ensure that lines of communication are open between personnel.
  • Discuss specific duties when jobs require more than one person to eliminate any questions.
  • Always look out for co-workers with safety in mind.

6. Fatigue

Fatigue is a major human factor that has contributed to many maintenance errors as a result of accidents. Fatigue can be mental or physical. Emotional fatigue is also present and affects mental and physical performance. Stress and overworking can also lead to fatigue.

A fatigued person may be easily distracted. He or she may experience abnormal mood swings. Fatigue results in an increase in mistakes, poor judgment, and wrong decisions. A fatigued person may also lower his or her standards.

Eliminate fatigue related performance issues

  • Watch for symptoms of fatigue in yourself and others.
  • Have others check your work.

7. Lack of Resources

Lack of resources includes not having enough manpower, equipment, documentation, time, parts, etc., to complete a task.

When there is a lack of resources available to properly fix something, it should be decided to stop maintenance until the appropriate parts are available. Never replace a part with one that is not compatible for the sake of getting the job done.

Improve supply and support

  • Order parts before they are required.
  • Have a plan for pooling or loaning parts.
  • Preserve all equipment through proper maintenance.

8. Pressure

Aviation maintenance tasks require individuals to perform in an environment with constant pressure to do things better and faster without making mistakes.

The pressure to fix things is always present in aviation. Maintenance personnel should not allow time pressures to get in the way of finishing maintenance safely.

Reduce the burden of physical or mental distress

  • Communicate concerns.
  • Ask for extra help if time is an issue.
  • Put safety first.
  • Ensure that the pressure is not self-induced.
  • Communicate if you think you will need more time to complete a repair rather than rush through it.

9. Lack of Assertiveness

Lack of assertiveness occurs when a person is not self-confident enough to speak up for their rights and ideas. Failure to speak up or document concerns about instructions, orders, or the actions of others.

Lack of assertiveness in failing to alert others when something does not seem right can result in many fatal accidents. Do not let something that you know is wrong continue by ignoring it.

Express your feelings, opinions, beliefs, and needs in a positive, productive manner

  • Express concerns but offer positive solutions.
  • Resolve one issue before addressing another.
  • Provide clear feedback when a risk or danger is perceived.
  • Never compromise your standards.
  • Allow coworkers to give their opinions and always accept corrective criticisms.

10. Stress

Stress is a physical, chemical, or emotional factor that causes physical or mental tension.

Aviation maintenance is always a stressful task due to many factors. Aircraft must be airworthy and flying in order to make money for any airline. This means that maintenance must be done within a timeline to avoid flight delays or cancellations.

Stress is the subconscious response to the demands placed on a person.

Manage stress before it affects your work

  • Take a rational approach to problem solving.
  • Take a short break when needed.
  • Discuss the problem with someone who can help.
  • Healthy eating, exercise, and a sufficient amount of rest can reduce stress levels.

11. Lack of Awareness

Lack of awareness is a failure to recognize a situation, understand what it is, and predict the possible results. It is a failure to recognize all the consequences of an action or lack of foresight.

After completing the same tasks multiple times, maintenance personnel can develop a lack of awareness for what is around them. They tend to lack common sense and vigilance because they have completed the same task so many times.

See the whole picture

  • Make sure there are no conflicts with existing repairs or modifications.
  • Fully understand the procedures needed to complete a task.
  • Always ask coworkers to check your work.

12. Norms

Norms are short for “normal”, or the way things are normally done. They are unwritten rules that are followed or tolerated by most of the organization. Negative norms can detract from the established safety standard and cause an accident to occur.

Be aware that just because it seems normal does not make it correct. The easiest way of accomplishing something may not be the standard.

Help maintain a positive environment with your good attitude and work habits

  • Existing norms don’t make procedures right.
  • Ensure that everyone follows the same standard.
  • Follow good safety procedures.
  • Identify and eliminate negative norms.

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