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Cents Worth


Maintenance engineers and mechanics have known about ‘The Dirty Dozen’ for years. No, I’m not talking about the 1967 war movie. Rather, I mean the 12 most common human error preconditions or conditions that act as precursors to accidents or incidents for mechanics.

I first learned about The Dirty Dozen when I put together a crew resource management course for helicopter engineers and mechanics. I instantly realized that pilots would be safer if they knew about these dozen error traps too.

The Dirty Dozen is a concept developed in 1993 by Gordon DuPont, when he worked for Transport Canada. They have since become a cornerstone in maintenance training courses worldwide.


1. Lack of Communication 2. Complacency 3. Lack of Knowledge 4. Distraction 5. Lack of Teamwork 6. Fatigue 7. Lack of Resources 8. Pressure 9. Lack of Assertiveness 10. Stress 11. Lack of Awareness 12. Norms

The Dirty Dozen can affect our performance and should be remembered by anyone working in and around aircraft, whether pilot or mechanic. Let’s dissect these dozen culprits more closely.


Studies have shown that generally only 30 percent of verbal communication is received and

6 May 2015

understood by either person in a conversation. People normally remember what was said first and last in an exchange; consequently it is important to put the most important part of our message first and then repeat it at the end. Depending on the complexity of the message, it might be more effective to provide some form of written instruction, such as a checklist.


Complacency is defined as “self-satisfaction accompanied by a loss of awareness of the danger.” If an activity has become routine and we’re feeling fat dumb, and happy, we may be missing important signals because we tend to see what we expect to see.


Air operators have a regulatory responsibility to ensure that their personnel have required training. Pilots and mechanics should always keep up to date on relevant information to perform their jobs safely.


Distraction is anything that draws our attention away from the task at hand. Psychologists say distraction is the number one cause of forgetting things. We are always thinking ahead, thus we have a natural tendency when we are distracted before returning to a job to think we are further ahead than we actually are.

LACK OF TEAMWORK An effective team will:  Maintain a clear mission  Maintain team expectations  Communicate to all team members  Maintain trust  Pitch in FATIGUE

Scientific studies have shown that, similar to being under the influence of alcohol, when

fatigued we tend to underestimate the problem and overestimate our ability to cope with it. It’s been proven that after 17 hours of wakefulness we are functioning as if we had an equivalent blood alcohol level of 0.05 percent. After 24 hours, the level increases to 0.1 percent. It is also noteworthy that the more fatigued we are, the more easily we become distracted.


A lack of resources can interfere with our ability to complete a task because there is a lack of supply and support. Low-quality products also affect our ability to complete a task.


Urgent demands that can influence our performance include: 1. Company demands 2. Client demands 3. Peer demands

4. Self-induced demands

Interestingly, of these four demands, we put the most pressure on ourselves. Self-induced pressures are those occasions where we take ownership of a situation not of our doing. The “monkey on our back” is ours because we accepted and took ownership of it. Being assertive and not accepting said monkey will help distance us from the assumed “urgency” of the induced pressure to perform.


is feelings, the ability to express our opinions, beliefs, and needs in a

positive, productive manner. It is not the same as being aggressive.

The following are examples of how a lack of assertiveness can be offset.

 Get the persons attention and state the problem:

“John, I have a concern with…”

By Randy Mains

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