Fatigue in Aviation Maintenance Environments

Fatigue in the aviation maintenance workplace is a long standing issue according to the National Transportation Safety Board (NTSB). Since 1997, the NTSB has maintained this issue on their Most Wanted List. The NTSB’s most wanted list is comprised of the most critical aviation safety improvements

necessary in the eyes of the Board. The item was added to the list after a few accidents ended with fatigued mechanics or inspectors as one of the contributing factors.

The Most Wanted List item # A-97-71(FAA) specifically demand the Federal Aviation Administration (FAA) “review the issue of personnel fatigue in aviation maintenance; then establish duty time limitations consistent with the current state of scientific knowledge for personnel who perform maintenance on carrier aircraft”. (NTSB 1999)
According to the NTSB, the FAA’s response and actions taken are not acceptable to mitigate the risk of aircraft accidents due to technician or inspector fatigue.

What Has the FAA Done?
AAR-100 is the FAA’s Human Factors Division. This division has a sub-division focused solely on human factors in aviation maintenance. In 1998, after an agreement with the FAA, Galaxy Scientific spearheaded an effort from industry experts to publish Human Factors Guide for Aviation Maintenance. In 1999, the division issued a report titled Study of Fatigue Factors Affecting Human Performance in Aviation Maintenance. From the human factors guide by Galaxy Scientific, the FAA determined that more research was necessary to understand how fatigue affects the safe performance of aviation maintenance. It was decided the best approach would be to employ the services of an outside entity to have independent research in the subject. In the mean time, the FAA revised its Advisory Circular (AC) 120-72 Maintenance Resource Management Training to include information that should be a part of the training to cover the risk of fatigue.

The study was completed in 2001 by a team from Embry-Riddle and Galaxy Scientific. The document titled Evaluation of Aviation Maintenance Work Environments, Fatigue, and Human Performance provided great insight into the issue. The results of the study will be discussed further later in this paper. The FAA took the actions recommended in the study, which will be discussed further also.
Presently, the NTSB is not satisfied with the FAA’s approach since no regulatory action has been made in the matter.

What is Fatigue?
We have all experienced fatigue. There is sometimes confusion in distinguishing fatigue from tiredness. The two are not interchangeable. One definition of fatigue is ‘Decreased capacity or complete inability of an organism, organ, or part to function normally because of excessive stimulation or prolonged exertion’. (Orlady & Orlady 1999) The excessive stimulation and prolonged exertion in an aviation maintenance environment can be due to many factors. Lighting, vibration, extreme temperatures, and the mere tediousness of a task are some of the factors. It is the NTSB’s contention that the resulting fatigue from these factors have been contributions to some accidents and will certainly be in future accidents.

The 2001 Study
As stated previously, Aviation Maintenance Work Environments, Fatigue, and Human Performance was undertaken to provide insight to just how fatigue might play a role in an accident. In this study, one-hundred randomly selected aviation maintenance personnel agreed to wear monitoring devices for a two-week period. These devices measured temperature, lighting, sound levels, and sleep conditions.

The second half of the study was done in the form of a questionnaire filled out by five-hundred aviation maintenance personnel; also selected randomly.
The study covered more areas than just fatigue related issues. This paper will attempt to stay in line with fatigue causing factors only.

Sleep Patterns
The results concluded that the subjects slept on average of five hours per night. The researchers utilized the results of a Gallup poll conducted on the general public in 1997 as their measure of how much sleep an individual needs to feel alert. The optimal time according to this poll was just over seven hours.

Participants selected a button on the device when they went to bed to indicate they were going to sleep. The device only counted one as actually sleeping if the instrument was not moving; meaning the person must be totally still in order for the measurement to be accurate. Otherwise, the time was counted as pre-sleep, or a falling asleep period.
There were differences between the amount of time subjects reported they were sleeping versus the amount of time the device reported they were sleeping.

In general, the participants answering the questionnaire felt they worked with inadequate lighting. They also felt that poor lighting has a negative impact on their job performance. The study concluded that the survey data was likely more accurate than the monitoring equipment because the survey was based on people’s perception. It was noted that the study could not conclude how inadequate lighting affects performance.

Shift Work
The survey portion of the study revealed that a very large percentage of participants who work the night shift indicated that they feel frequent fatigue at work. Those who work the day shift did not report feeling fatigued as often at work. This suggested to the researchers that those on the night shift were at greater risk of degraded performance than those working during the day.

Most of the participants themselves did not feel that the fatigue they felt affected their work performance at all. The largest population indicating their work was affected were those on the night shift.

Temperature and Sound Pressure
The data was listed in the study, but no analysis was given. It was only indicated that Phase 3 of the study would attempt to identify how this data correlates to fatigue.

Study Observations/Recommendations
The researchers determined that the lack of sleep is a cultural issue that can only be addressed by training. They concluded that it is likely that the personnel are simply unaware of the recommended sleep needed to function properly. The training would educate the workforce on how fatigue can put them at risk for making a mistake and how to recognize signs of fatigue.

Although the data on temperature was not analyzed, the recommendation was made to educate the workforce on how temperature can affect job performance. The training should also include mitigation strategies, such as having water available to those who are working in high heat environments.

For sound and noise levels observed, the recommendation was to refer to the Human Factors Guide for Aviation Maintenance, as this publication addresses mitigation strategies for those working in high noise environments.

Writer’s Evaluation
This study conducted appears to be faulty in many ways. It was evident that the data collected by the sleep monitoring device was likely inaccurate if the device only counts one as sleeping if they are not moving. It would also seem that the researchers could have utilized a more scientific based set of standards for sleep than a Gallup Poll. Some of the data collected in the research was not even analyzed in the study, only reported. This data on things such as sound and temperature levels would seem to be very valuable in providing a complete assessment of fatigue levels.

With the information collected and the way in which it was analyzed, the only recommendation the researchers could make was training. Another factor working against them attempting to make any other recommendation than training is the fact that there has been no research done to measure how and when fatigue of maintenance personnel has attributed to failures in the system. That information would need to be available to substantiate any type of regulatory action by the FAA on duty time limitations. The researchers acknowledge this in their closing remarks. Phase 3 of the study has yet to be conducted. It is not known why the FAA has not funded this activity.

Pilots versus Mechanic Duty Limits
The NTSB feels that mechanics should be held to duty time limitations the same as pilots. The writer disagrees with this. Pilots flying an aircraft cannot go take a break. They are literally stuck in their work environment. Weather changes constantly create challenges. Pilots also must be alert enough at all times during flight to implement any one of hundreds of contingency actions in a split second. Duty time limitations are warranted easily if these circumstances are taken into consideration.
Mechanics, on the other hand do have the option to take a break at any time. They normally are not working in conditions where contingency actions are required instantaneously. Mechanics need an awareness and education about how fatigue can potentially lead to inadvertent unsafe acts.

Industry Culture Change
The Centre for Applied Behavior Research as the University of Southern Australia is known for being a world leader in the study of how fatigue affects safety of job performance. The Centre contends that a lack of sleep and shift work are the two most important causes of fatigue. Based on research done in the university’s Sleep Centre, it was discovered that fatigue can be most closely compared to being under the influence of alcohol beyond legal allowable limits. One’s judgment is affected as well as the ability to react and reason logically. The Centre worked with the Australian Rail Industry and the Australian Air Force to develop a comprehensive fatigue management program. The program consists of education, fitness for work testing, and a software based fatigue modeling and management system. Currently, the aviation industry and others are working with the Centre and following suit with the same types of programs.

The issue of fatigue is seen as one that needs to be addressed by the employer and the employee. Legislation will not change the lifestyles of individuals. Employers must have the flexibility to arrange schedules to meet production requirements. Employees have the responsibility and the right to stop and ensure they are fit to perform the safety sensitive functions for which they are employed.
The FAA’s Aviation Safety Team is in full force educating mechanics, as are the Professional Aviation Maintenance Association along with many other industry groups. The key is finding a balance between the mechanic’s and employer’s needs. The risk can be managed without federal laws. This is obviously the conclusion of the FAA and other experts in the field of human behavior and human factors.

Folkard, S. (2002). Work Hours of Aircraft Maintenance Personnel Civil Aviation Authority, CAA Paper 2002/06
Dawson, D. (2001b) Field Based Evaluations of a Work Related Fatigue Model Based on Hours of Work Transportation Research Part F
Orlady & Orlady (2005) Human Factors In Multi Crew Flight Operations Chapter 9
NTSB (1997) A-97-71
FAA (2003) AC120-72 Maintenance Resource Management Training
FAA (1999) Study of Fatigue Factors Affecting Human Performance in Aviation Maintenance
Galaxy Scientific (2001) Human Factors Guide for Aviation Maintenance