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My Two Cents Worth - May 2015

Posted 9 years 6 days ago ago by Admin


Maintenance engineers and mechanics have known about ‘The Dirty Dozen’ for years. They are 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.

The Dirty Dozen:

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.

Lack of Communication

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

Lack of Knowledge

Air operators have a regulatory responsibility to ensure that their personnel have required training. A pilot or mechanic should always keep up to date on relevant information to perform their job 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


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.

Lack of Resources

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.

Lack of Assertiveness

Assertiveness is the ability to express our feelings, 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…”
  • Give consequences:
  •     “If we continue… this will be the result…”
  • Offer solutions:
  •     “We could… You may want to try… I’d like to…”
  • Solicit feedback:
  •     “What do you think?”

In all of the above scenarios, remember to deal with one issue at a time (not multiple issues), do not embellish or exaggerate, stick to the facts, and remain calm.


There are two types of stress: acute and chronic. Acute stress relates to the demands placed on the body because of current issues like time constraints for readying an aircraft for flight. Chronic stress results from long-term demands placed on the body by negative major life events such as divorce and financial worries, or positive events like having a child. Chronic stress can exaggerate the effects of acute stress. To handle acute stress, take a short break and relax by deep breathing. Dealing with chronic stress is more difficult and usually involves a lifestyle change.

Lack of Awareness

This is defined as “a failure to recognize all the consequences of an action, or lack of foresight.” To combat lack of awareness, try asking yourself these questions: What if…? Do I see the complete picture? What have I forgotten?


Norms are unwritten rules or behaviors in an organization that are dictated, followed, and supported by the majority of the group. With norms, they have become part of the company’s culture, often referred to as “the way we do things around here.”

Unfortunately, norms follow unwritten rules or behaviors that can deviate from well-proven rules, procedures, instructions, or SOPs. Norms can be enforced through peer pressure and force of habit. It is important to understand that most norms have not been designed to meet all circumstances, and therefore are not adequately tested against potential threats.

Keep The Dirty Dozen in mind while on the job. Just as awareness of them helps keep mechanics from making mistakes on the ground, they will help keep you safe in the air.

Safe Flying!

About Randy: Randy Mains is an author, public speaker, and a CRM/AMRM consultant who works in the helicopter industry after a long career of aviation adventure. He currently serves as chief CRM/AMRM instructor for Oregon Aero. He may be contacted at [email protected]