Human Error in Aircraft Maintenance

Human Error in Aircraft Maintenance

1- Introduction

            The present paper is an extensive investigation of the issue of different human factors involved in aviation operations specially maintenance of an aircraft. The paper investigates the causes and history of human error in maintenance and shed critical light on the historical development in aviation industry with regard to human error. Statistical and qualitative data have been included to get the gist of knowledge available in the area of human factors and human error. The paper examines specific errors, factors of errors in aircraft maintenance and suggests methods, procedures, and strategies to prevent and reduce these errors. The paper also points to the status of present day research in aviation with regard to human error.

2- Understanding Human Error

            According to Senders and Moray (1991), all humans have experienced human error. It occurs when someone interacts with complex systems, or machines. What we do is go over things that are contrary to what we intend to do. Thus in between the complexity of a system and the human intension while interacting with that system does a human error occur. It can be anything from unnoticed inconvenience to a “genuine catastrophe”. Therefore, a human error takes place while we put effort to maintain any complex systems which are the result of today’s modern lifestyle. Such an error can occur in management of the system, its design, operation, and so forth. Today our dependence on these systems for our well being tells that human error is also a strong and repeatedly occurring phenomenon that can lead to “hazard to human life and welfare, and to the ecosystems of Earth”. Human error has been an active factor in a number of devastating calamities: the aerospace accidents of Three Mile Island, Bhopals, and Chernobyls. Of errors that result in massive costs and accidents are “merely the tip of the iceberg”. Otherwise, around the globe every day people make errors that fortunately do not result in calamities. Although there have been attempts to understand human errors, its sources, and its possible consequences, to date, very little systematic study to understand human error has been done. One reason can be that human error is commonly taken as “a result or a measure of some other variable, and not as a phenomenon in its own right”; Kollarits’ “phenomenological” taxanomy (1937) is one of the earliest attempts to gauge the factor of human error. However, looking at the three major aerospace accidents, the need to study human error systematically is highly urgent. (pp. 1-5). Errors can be of “perception, intention, and execution”. To communicate to non-specialists, error classification can be as in “omission, substitution, insertion, and repetition”. Exogenous and endogenous are the two classes to gauge whether an error was on design or merely because of misfunctioning. Today, there is need to prepare a variety of taxonomies so that several tasks can be analyzed to learn more about human errors (pp. 50-55).

3- Human Factors in Aviation

In aviation, study of human behaviors, capabilities, and limitations are considered in the category of human factors. These factors are integrated into the systems designed for people keeping in mind the primary objective of improving safety, overall well-being of the people who operate such systems, and the performance of the systems. The founders of aviation did have concerns for human factors involved in flight procedures and they tried as such to improve upon it although in the very beginning the purpose of flying were only adventure and fun-making as well as discovery. Although majority of the earliest accidents took place mainly due to structural failures, studying human factors in aviation as an identified discipline of science was not done; the major focus in early days was to inform the pilot of various constraints present in making a flight. However, it is in the pre-World War I days that we find the roots of human factors in aviation and their recognition; it was due to the increased and critical role of airplanes in the warfare. Thus, human factors emerged as essential in the selection process of the pilot who was required to have certain characteristics to acquire the training of pilot: initially, “family background, character traits, athletic prowess, and recommendations from significant persons” (Jefferson, pp. 1-5, 1999). Throughout the jet era, human error has been attributed in part or whole responsible for 65 to 80 percent of accidents in air transport. Today manufactures and operators are constantly putting efforts to decrease the role and frequency of human error; thus the entire focus sees the automation of more and more task of the pilot; similar efforts are being put in the area of traffic control system. However, it is a burning question whether automation is the sole solution of the problem of air accidents. Data from last twenty years shows that although automation and advancement in technology and its use in aviation has reduced certain types of accidents, it is still a matter of fact that some grave areas do pose serious questions when it comes to the use of technology and adoption of automation. There are experts who view that automation cannot completely eliminate the factor of human error; and thus the struggle continues to date (Billings, pp. 1-6, 1997).

4- Aircraft Maintenance and Human Error

            Human error in aircraft maintenance generally appears to be an unintended discrepancy in aircraft attributable to non-actions or actions of the AMT (aircraft maintenance technician). Any maintenance task undertaken for aircraft also gives an opportunity for human error and consequences related to it. There are two types of basic forms of human errors that can take place in the maintenance process of an aircraft. The first case is when a discrepancy takes place after a maintenance task when this discrepancy was not there before. This can, for example, take place in the in the “failure to remove a protective cap from a hydraulic line before reassembly”, wrong installation of line-replaceable units, or the damaging of objects like air duct when a task was initiated. The other type of error is when an unsafe or unwanted operation takes place due to human error “while performing a schedule or unscheduled maintenance task designed to detect aircraft degradation”; examples of this type are, no notice being taken of structural crack when a visual examination was undertaken; or a defected avionics box sitting on aircraft just because incorrect examination of the problem had the wrong box removed. There are various reasons why such errors in maintenance take place. For instance, these maintenance errors can occur due to underprovided training of the AMT; meager allocation of funds and resources, non availability of some of the maintenance tools, poor allocation of maintenance tools, pressure of time, and so forth. Poor ergonomic layout of tools can also cause human error to take place (e.g., L-H faulty interface); missing manuals or incomplete documentation is reported to be another cause of human error in aircraft maintenance (e.g. L-S interface defect). A number of accidents have been reported to be caused by human errors committed in the maintenance task of an aircraft: the American Airlines DC-10, Chicago, 1979 occurred because of error in engine maintenance. Similarly, Boeing 747 (Japan Airlines) went through an instant decompression in the air when bulkhead failed because it was not properly repaired. As such there are a number of instances that clearly show that human error maintenance was a primary cause of the accidents (both L-H and L-S combined or separately). For example, when 93 of the major accidents (occurring between 1959 and 1983) world-wide were examined in details, it was noticed that 12% of these accidents were caused by the factors of maintenance and inspection. The following chart of that analysis depicts that various causes of the errors:

(source: Civil Aviation Authority, 2002.  www.caa.co.uk).

Another important observation comes from the fact that Civil Aviation Authority of the UK (UK CAA) has published a report in which major maintenance problems and discrepancies have been noted. These tell us that human error in maintenance is a very critical area. The areas reported are as follows:

Wrong installation of different components
Wrong parts being fitted
Discrepancies of electric wiring
Leaving loose objects in aircraft like tools, etc.
Falling short of lubrication
Panels, cowlings, etc. remain unsecure
However, an analysis of engineering related issues and human error pointed out to four major areas where errors of maintenance are most likely to take place. There are: (i) omission being 56%; (ii) wrong installation being 30 percent; (iii) wrong components being 08%; and (iv) others being 06%.  (caa.co.uk, 2002).

5- Human Error and in the Maintenance Environment

            Contrary to real-time nature of errors committed while the airplane is on flight, the errors committed in the maintenance face are not identified at the time when an error was made. This is even more likely to happen that a maintenance technician never knows whether they have made an error because it is possible that the detection of such an error might take much longer than on-flight errors. It is usually a malfunction of performance that we know some kind of error might have been committed in maintenance because “What is rarely known is why the error occurred”. When pilot errors are broken down into a number of lines, it is surprising to note that errors related to maintenance only get online: “maintenance and inspection deficiencies”. Analysis of three major air accidents reveals that maintenance environment errors in the three cases were similar to each other. These are as follows:

§          Personnel of inspection and maintenance failed to conform to established procedures and methods (known as active failure)

§          The other personnel who were responsible to ensure conformity to established rules and procedures failed to supervise “not in ‘one-offs’ but in what were symptomatic of longer-term failures (active and latent failures)”.

§          Positive actions were note taken by higher level management hence compliance with methods and procedures were observed at a short level.

§          Maintenance work was done by a maintenance worker who was assigned for a specific job or they started working on their own.

§          It was a notable similarity in the three cases that lack of communication was the basic factor playing role in the human errors committed in maintenance. (acc.co.uk, 2002).

6- Prevention of Human Error in Aircraft Maintenance

            It has often been pointed out by research and empirical evidence that however obvious the causal issues of an accident may appear to the critical investigation, it is not possible that an accident took place in isolation. In other words, there are related issues and factors that combinedly lead to an accident. This has led to an analysis of finding out errors at different levels and how to prevent these errors at each level. Today maintenance related human errors have been studied and the lessons learned in the ninety years history of aviation have led us to develop procedures to help prevent those errors (acc.co.uk, 2002).

The basic area to start work to prevent human error in maintenance of an aircraft starts from classification of errors in different areas from overhauling to tightening a screw or changing a defected part of the engine. There are certain prevention strategies that are recommended to be used to prevent human errors in maintenance. There are three major areas in which the prevention strategies for human errors are proposed. These are reduction or errors, capturing of errors, and tolerance for errors. Reduction of errors involves that there should be a direct attempt to reach to the source of error itself. Improving this reach to different parts of aircraft; improving the light system in which maintenance is done; improvement in the training of the technicians of the aircraft are some of the prevention strategies in the phase of error reduction. These are considered to abate chances of careless errors. The second area, capturing of error, is when it is assumed that an error in maintenance has been made. Thus, here the attempt to “capture” that error is made before the airplane takes off. Some examples of capturing mistakes can be post-task inspection, step by step verification within an assigned task, and tests of function and operation after a task has been performed. The third phase, error tolerance, “refers to the ability of a system to accept an error without catastrophic (or even serious) consequences”. In the phase of aircraft maintenance, error tolerance refers to two areas: one is the overall design of the aircraft; the other is the design of the entire maintenance system followed for an aircraft. Instances of error tolerance in aircraft maintenance can be as follows: on the aircraft, a number of electrical or hydraulic systems should be incorporated so that one human error can come to bear consequences only on one system; there should be multiple inspection opportunities so that a fatigue crack can be caught before that crack can reach to a critical length. Of the three strategies of prevention, the error reduction strategy is the only one that addresses the human error directly. The other two strategies, error capturing and error tolerance, are linked directly with the integrity of the system. “From a system safety perspective, human error in maintenance does not directly or immediately cause an aircraft to be unsafe”. Unless it is the case that maintenance technician is working on in-flight aircraft, this would be the case always (caa.co.uk, 2002).

7- Gap between Maintenance and Psychology

What is important is that the gap between maintenance technicians and psychology (with relation to the operation of aviation) should be narrowed as much as possible for better result. Although pilot community and the industry related psychologists have been working together to work out a number of problem present to the pilot community, with a few exceptions, manufacturers, aircraft designers, maintenance technicians, and field psychologists have been two worlds apart which says much about the present challenges with regard to the maintenance and presence of human errors in maintenance. It is therefore important that psychologist and maintenance technicians find a common ground to work for the betterment of the maintenance systems so that errors and chances for human errors can be directly addressed and prevented. Today, it is highly demanded of the aviation psychologists that they “must move beyond the individual human-machine interface issues to a collective systems analysis approach”.

8- Research in Aviation

            Human factors in aviation came to find a substantial place in World War II and proper developments, tests, research, evaluation cycle were seen emerging on the serious grounds of study. This step ahead became possible due to the role played by the human-machine system and the grave results of human error. Thus, considerable research found its place in the discourse of aviation that led to significant insights. However, with the end of the Cold War military spending shrank and so the funding for research on human factors. Today strategic focus on human factors and errors is what is seen as the most critical area of study in the departments of “research, development, testing, and engineering” (RDT&E). Today, the research in aviation include: decision making on command-level, advanced automation in cockpit, ways of improving decision making at command-level in control staff and Navy, and the betterment of 3-D audio system, to name a few. It is the central focus of the present research to reduce, as much as possible, the role of human factors in the operation of technology and thus reducing the role of human errors in aviation and maintenance of an aircraft. Testing issues like compliance and verification are at the uppermost layer of all the present research of gauging human factors and human eorrors (Jeffrey, pp. 15-19, 1999).

9- Conclusion

Human error has been a likely factor in a number of malfunctions of in-flight malfunction throughout the history of aviation. Although considerable efforts have been put to reduce human errors from operation, this has essentially been done in the area of pilot community and maintenance department has not received the required amount of attention. Major reason for this is the fact that maintenance errors are not diagnosed directly on the system which is a weak area of today’s aviation and which is now receiving inclined attention. What is needed for prevention of human error in aircraft maintenance today is that different departments must work together in harmony to each other so that a safe and sound flight can become a reality of the present aviation industry which is expanding by the moment.
Works Cited

Billings, C. E. (1997). Aviation automation: the search for a human-centered approach. Mahwah, NJ: Lawrence Erlbaum Associates, pp. 1-20.

Caa.co.uk (2002). Human errors in aircraft maintenance and inspection: safety regulation group. Retrieved on December 15th from: http://www.deepsloweasy.com/HFE%20resources/CAA%20HFE%20in%20Aircraft%20Maint%20and%20Inspect.pdf

Jefferson, M. K. (1999). “A historical overview of human factors in aviation”. In Handbook of aviation human factors, (Daniel J. G., J. A. Wise, & V. D. Hopkin, Eds.). Mahwah, NJ: Lawrence Erlbaum Associates. pp. 1-5.

Jeffrey, G. (1999). “The role of human factors research in avitaion”. In Handbook of aviation human factors, (Daniel J. G., J. A. Wise, & V. D. Hopkin, Eds.). Mahwah, NJ: Lawrence Erlbaum Associates. pp. 15-20.

Senders, J. W., & Moray N. P. (1991).  Human error: cause, prediction, and reduction. Hillsdale, NJ: Lawrence Erlbaum Associates, pp.1-55.