The Dirty Dozen: Common Human Error Factors in Aircraft Maintenance Mishaps

To better equip aircraft maintainers to combat the risks they encounter daily, Air Education and Training Command Safety (AETC) is leveraging what one safety expert termed “The Dirty Dozen.” This list identifies 12 of the most common human error factors leading to aircraft maintenance mishaps. This list is by no means all-inclusive, but it includes some of the most frequent elements that influence people in the maintenance community to make mistakes. Understanding these hazards enables maintainers to avoid costly and dangerous errors.

Whether maintaining a legacy airframe with decades of “lessons learned” or a fifth generation aircraft with advanced automated aircraft health management and troubleshooting systems, The Dirty Dozen affects everyone.

“When we choose to let these 12 human factors catalyze unnoticed, the probability and severity of mishaps increase,” said MSgt Clinton Gessler, AETC Safety Directorate Flight Safety Senior Noncommissioned Officer. “However, when we deliberately allocate time and energy toward accomplishing the basics of maintenance—tool accountability, FOD (foreign object damage) walks, cleaning up spills, following tech data, and paying attention to details—we reduce the likelihood of a mishap occurring.”

Drawing from SKYbrary (https://www.skybrary.aero/), an electronic repository of aviation safety knowledge, the following information identifies and defines The Dirty Dozen and provides suggested countermeasures to reduce risks posed by each of these hazards.

THE LIST

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

LACK OF COMMUNICATION

Poor communication often appears at the top of contributing and causal factors in accident reports and is, therefore, one of the most critical human factor elements. Communication refers to transmitter and receiver, as well as the method of transmission. Transmitted instructions may be unclear or inaccessible. The receiver may make assumptions about the meaning of these instructions, and the transmitter may assume the message has been received and understood. With verbal communication, it is estimated only 30 percent of a message is received and understood.

Detailed information must be passed before, during, and after any task, and especially across the handover of shifts. Therefore, when messages are complex they should be written down. Organizations should encourage full use of logbooks, worksheets, checklists, etc. Furthermore, for critical operations, such as towing or jacking an aircraft or conducting an engine run, ensure all team members understand their roles and expectations and what to do if things go wrong. This extra communication may add time to tasks, but even one mishap costs much more time to sort out and may result in loss of life.

COMPLACENCY

Complacency comes from familiarity with a task accompanied by loss of awareness of potential dangers. Such a feeling often arises when conducting routine activities that have become habitual and may be considered by an individual (sometimes by the whole organization) as easy and safe. With less vigilance, important warning signs can be missed.

Complacency can also occur following a highly intense activity, such as recovering from a possible disaster. The relief felt at the time can result in physical relaxation and reduced mental vigilance and awareness.

Although too much pressure and demand cause over-stress and reduced human performance, too little pressure results in under-stress, boredom, and complacency, which can also result in reduced human performance. Therefore, when conducting simple, routine, and habitual tasks, and when fatigued, it is important to maintain an adequate, or optimum, level of stress through different stimulation. Always assume you can make a mistake if not careful. Following written instructions and adhering to procedures that increase vigilance, such as inspection routines, can provide suitable stimulus. It is important to avoid working from memory, assuming something is okay when you have not checked it, and signing off on work you are unsure has been completed. Teamwork and mutual cross-checking provide adequate stimulus when fatigued. If supervising, be actively involved in the activities of your subordinates in a positive, motivating way. Effective leadership means helping our Airmen stay actively engage with their tasks by ensuring they perform with excellence, while also teaching them how to do so.

LACK OF KNOWLEDGE

The regulatory requirements for training and qualification can be comprehensive and organizations must enforce these requirements. Otherwise, lack of on-the-job experience and specific knowledge can lead workers into misjudging situations and making unsafe decisions. Aircraft systems are so complex and integrated that it is nearly impossible to perform many tasks without substantial technical training, current relevant experience, and adequate reference documents. Furthermore, systems and procedures can change substantially and employees’ knowledge can quickly become out-of-date.

It is important for employees to undertake continuing professional development and for the most experienced workers to share their knowledge with colleagues. Part of this learning process should include the latest knowledge on human error and performance. It should not be taken as a sign of weakness to ask someone for help or for information; in fact, this should be encouraged. Checklists and publications should always be referred to and followed. Never make assumptions or work from memory.

Finally, good leaders help their subordinates see value in investing in their own expertise. Encourage intellectual curiosity and independent study of the more technical subjects associated with aircraft maintenance.

DISTRACTION

Distraction could be anything that draws a person’s attention away from their task. Some workplace distractions are unavoidable, such as loud noises, requests for assistance or advice, and day-to-day safety problems requiring immediate solutions. Other distractions can be avoided or delayed until more appropriate times, such as messages from home, management decisions concerning non-immediate work (e.g., shift patterns, leave entitlement, meeting dates, administrative tasks), and social conversations.

Psychologists say distraction is the number one cause of forgetting things, hence the need to avoid becoming distracted and to avoid distracting others. Humans tend to think ahead. Thus, when returning to a task following a distraction, we tend to think we are further ahead than we actually are.

To reduce errors from distraction, it is best to complete a task before responding. If the task cannot be completed without hurrying, then we can prominently mark (or “lock off”) the incomplete work as a reminder to ourselves and anyone else who may complete the work. When returning to work after being distracted, it is a good idea to commence at least three steps back, so we retrace some steps before picking up the task again. If necessary, having someone else double-check our work using a checklist may be appropriate and useful.

Management has a role to play in reducing the distractions placed on their employees. This may involve good workspace design, management of the environment, and procedures that create “safety zones,” “circles of safety,” or “do not disturb areas” around workers engaged in critical tasks.

Finally, when approached by a co-worker during a critical task, Airmen of all ranks are encouraged to respectfully communicate their need to complete the task before responding. If you need a minute to get to a logical pause in what you are doing, say so. “Can I get back to you in three minutes? I’m on step two of four on this checklist, and I don’t want to miss anything.”

LACK OF TEAMWORK

In aviation, many tasks and operations are team affairs. No single person (or organization) can be responsible for the safe outcomes of all tasks. However, if someone is not contributing to the team effort, this lack of effort can lead to unsafe outcomes. Workers must rely on colleagues and outside agencies, as well as give others their support. Teamwork consists of many skills each team member needs to prove competence.

Some key teamwork skills include leadership, followership, effective communication, trust building, motivation of self and others, and praise giving. To create an effective team, it is necessary that the following issues, as appropriate, are discussed, clarified, agreed on, and understood by all team members:

• Clearly defined and maintained aim(s) or goal(s)
• Each team member’s roles and responsibilities
• Communication messages and methods
• Limitations and boundaries
• Emergency procedures
• Individual expectations and concerns
• What defines a successful outcome
• Debriefing arrangements
• Team dismissal arrangements
• Opportunities for questions and clarification

A team’s effectiveness can also be improved through the selection of team members to reflect a broad range of experience and skill sets, as well as through practice and rehearsal.

Good team players ensure the team is all on the same page before any critical task.

FATIGUE

Fatigue is a natural physiological reaction to prolonged physical and/or mental stress. We can become fatigued following long periods of routine work and shorter periods of hard work. When fatigue becomes a chronic condition, it may require medical attention, but workers should never self-medicate! As we become more fatigued, our ability to concentrate, remember, and make decisions reduces. Therefore, we are more easily distracted, and we lose situational awareness. Fatigue can also negatively affect a person’s mood.

Fatigue self-management involves a three-sided program of regular sleep, healthy diet (including reduced use of alcohol), and exercise. Work of a critical and complex nature should not be programmed during the low point on the body’s circadian rhythm (usually 3 to 5 a.m.). In addition, when fatigued, always get someone else to check your work.

Moreover, it is estimated that 80 percent of the body’s calories are burned by the brain as it processes the complex problems we encounter daily. Some maintenance tasks are physically challenging, but long hours of problem-solving and intense mental engagement can create fatigue as well.

Finally, if you feel tired but your mission demands you continue, communicate your fatigue to your team and supervisor. Your supervisor needs to know if your decision-making suffers or your fatigue otherwise makes your situation hazardous for you or your teammates.

LACK OF RESOURCES

If all parts are not available to complete a maintenance task, there may be pressure to complete the task using old or inappropriate parts. In addition, a lack of other resources—whether personnel, time, data, tools, skill, experience, or knowledge—can interfere with one’s ability to complete a task. In some cases, the resources available, including support, are of low quality or inadequate for the task.

When the proper resources are available and at hand, there is a greater chance we will complete a task more effectively, correctly, and efficiently. Therefore, forward planning to acquire, store, and locate resources is essential. Properly maintaining the available resources, including the humans in the organization, is also key.

Ensure resource shortfalls are communicated to your supervisor, and if you are a supervisor, ensure they are passed up the chain of command. Commanders may have to assume risk to complete mission tasks without sufficient resources, but they rely on you to ensure they are aware of where those gaps are. Do not assume someone else informed leadership about the problem, and guard against cutting corners to “make it happen” without the required resources to complete the mission.

PRESSURE

Pressure is to be expected when working in a dynamic environment, especially in combat. However, when pressure to meet a deadline interferes with our ability to complete tasks correctly, then it has become too much. It is the old argument of quantity versus quality, and in aviation, we should never knowingly reduce the quality of our work. Pressure can be created by lack of resources, especially time, and from our own inability to cope with a situation. We may come under direct or indirect pressure from the organization/company, clients, and even our colleagues. However, one of the most common sources of pressure is within us. We put pressure on ourselves by taking on more work than we can handle, especially other people’s problems, by trying to save face or positively promoting superpowers we do not possess. These poor judgments are often the result of making assumptions about what is expected of us.

Learning assertiveness skills allows a worker to say, “No! Stop!” and communicate concerns with colleagues, clients, and the organization. These skills are essential. When deadlines are critical, then extra resources and help should always be obtained to ensure the task is completed to the required level of quality.

The bottom line is we need to generate airpower at the right time and place to achieve the desired effects in combat. However, a task done poorly may cause mission failure, and an on-time failure is still just that: failure.

LACK OF ASSERTIVENESS

Being unable to express our concerns and not allowing others to express theirs creates ineffective communications and damages teamwork. Unassertive team members can be forced to go with a majority decision, even when they believe it is wrong and dangerous to do so.

Assertiveness is a communication and behavioral style that allows us to express feelings, opinions, concerns, beliefs, and needs in a positive and productive manner. When we are assertive, we also invite and allow others to assert themselves without feeling threatened or undermined. Speaking one’s mind assertively is not to be confused with aggression. It is about communicating directly, honestly, and appropriately, giving respect to the opinions and needs of others without compromising our own standards.

Assertiveness techniques can be learned. They focus on keeping calm, being rational, using specific examples rather than generalizations, and inviting feedback. Most importantly, any criticisms should be directed at actions and their consequences rather than people and their personalities. This approach allows others to maintain their dignity and a productive conclusion to be reached.

Any Airman is empowered to call, “Knock it off!” before a mishap occurs. It is better to stop, take a breath, and ensure critical steps have not been overlooked before metal gets bent or people get hurt.

STRESS

There are many types of stress. Typically, there are two distinct types in the aviation environment—acute and chronic. Acute stress arises from real-time demands on our senses, mental processing, and physical body, such as dealing with an emergency or working under time pressure with inadequate resources. Chronic stress is accumulated and results from long-term demands on an individual’s physiology by life’s demands, such as family relations, finances, illness, bereavement, divorce, or even winning the lottery. When we suffer stress from these persistent and long-term life events, it can mean our threshold of reaction to demands and pressure at work can be lowered. Thus, at work we may overreact inappropriately, too often and too easily.

Some early visible signs of stress include changes in personality and moods, errors of judgment, lack of concentration, and poor memory. Individuals may notice difficulty in sleeping and an increase in fatigue, as well as digestive problems. Longer-term signs of stress include susceptibility to infections, increased use of stimulants and self-medication, absence from work, illness, and depression.

It is important to recognize the early signs of stress and to determine whether it is acute or chronic. Coping with daily demands at work can be achieved with simple breathing and relaxation techniques. Perhaps more effective is having channels of communication readily available through which to discuss the issue and help to rationalize perceptions. It is entirely appropriate some of these channels involve social interaction with peers.

These changes must be achieved with support from the organization. Organizations should, therefore, have employee assistance (or well-being) policies that include stress reduction programs.

As with many of these factors, communication is key. Let your supervisor know if your personal stressors are affecting you at work. They may not be aware of how factors external to what they see when you are at work may be adding to your total stress.

LACK OF AWARENESS

Working in isolation and only considering one’s own responsibilities can lead to tunnel vision, a partial view, and a lack of awareness of how our actions can affect others and the wider task. This lack of awareness may also result from other human factors, such as stress, fatigue, pressure, and distraction.

One problem with “channelized” attention is it prevents you from noticing key events happening around you that may affect your task. If you are so focused on prepping for an engine run that you fail to notice someone else “borrowed” your fire bottle before the start, you may wish you had been aware of what was happening so you could intervene at the time, rather than delaying the engine run for 30 minutes to find the required fire suppression.

Additionally, you may lack awareness of how your task relates to everything that comes after it. Understanding the “why” helps you remember the “how” to do it correctly and “what” can result if you do not. It is important to build experience throughout our careers, especially concerning the roles and responsibilities of those we work with and our place in the wider team. Developing our foresight is essential in preempting the effects our actions may have on others. Furthermore, asking others to check our work and challenge our decisions helps us gain relevant experience and expands our awareness as well as theirs.

Combat lack of awareness through good communication and asking questions. If you do not know “why” you are doing something, ask! If your supervisor does not have time to explain it, hold on to your question and follow up with them once the task at hand is complete. If you are the supervisor, anticipate “why” questions and answer them as thoroughly as time/opportunity will allow. If you do not know the answer, admit it, find the answer, and follow up with your Airmen.

NORMS

Workplace practices develop over time, through experience, and often under the influence of a specific workplace culture. These practices can be good or bad, safe or unsafe. They are referred to as “the way we do things around here,” which become norms. Unfortunately, such practices follow unwritten rules or behaviors, which deviate from the required rules, procedures, and instructions. These norms can then be enforced through peer pressure and force of habit. It is important to understand most norms have not been designed to meet all circumstances and, therefore, are not adequately tested against potential threats. They also lack flexibility when the broader situation changes. Norms that were good enough on fourth generation fighters may not work for fifth generation aircraft, especially when every mistake costs much more to repair.

Compliance with regulatory guidance should be the first norm in any maintenance organization. Rules and procedures have been designed and tested and, therefore, ought to be enforced and followed rigorously. When workers feel pressure to deviate from a procedure or work around it, this information should be fed back so the procedure can be reviewed and amended, if necessary.

Study the written guidance and respectfully challenge the norm using factual data whenever possible. This challenge will require assertiveness and good communication, but if you are new to the unit, you may be the only one who is still outside the culture enough to see the real risk the norm creates. This may mean you stay on the outside a little longer, which can be tough, but you may save a life. Change must start somewhere, with someone bold enough to ask tough questions.

Ultimately, if you have alerted your chain of command to unsafe norms without success, changing norms may require you to go outside of your unit. If necessary, consider talking to wing safety or the wing Inspector General rather than accept a hazardous situation.

NOTE: Following is a link to the Airman Safety App (ASAP), which allows Airmen to report safety-related risks and close calls using the Airman Safety Action Report. Anyone, anywhere, with almost any device, can quickly and easily report safety-related problems involving personnel, equipment, or property. Remain anonymous if you wish. Reporting is the first step to obtaining a solution for improvement. Reporting is simple and only takes between three and 10 minutes. Click on the following link to start your report. It is fast and easy!
https://asap.safety.af.mil/#/