The Human Factor in Aviation Maintenance
Kenneth L. Arrington
Embry-Riddle University

Abstract
Aviation maintenance professionals have earned high levels of technical skills training associated with their profession, however research in a number of industrial sectors indicate that up to 80% of accident causes can be attributed to a breakdown in human interaction. Human error cannot be eliminated it is essential fact of the human condition (Maddox, 1998).
Maintenance professionals will always try to avoid making errors. Unfortunately, even the most highly trained and motivated professionals will make mistakes, however, with suitable understanding of the human factor and appropriate training, professionals can mitigate the consequences of errors. The human factor component of aviation maintenance can be grouped in four general categories: 1. Effective training for technicians and inspectors; 2. On the job safety of maintenance workers; 3. Human error that compromises public safety; and 4. Overall cost of maintenance errors.

The Human Factor in Aviation Maintenance
Aviation is an industry where mistakes mean lives are at risk. Airplanes have become more complicated and sophisticated in their evolution within the past 50 years. Maintenance technicians must continuously update their proficiency and knowledge in airplane repair because of the enormous differences in new and old aircraft that are presently in use (Maddox, 1998).
Aviation maintenance professionals have earned high levels of technical skills training associated with their profession, however research in a number of industrial sectors indicate that up to 80% of accident causes can be attributed to a breakdown in human interaction. Human error cannot be eliminated it is essential fact of the human condition (Maddox, 1998).
The science of human factor has been established [resolutely] in the Aviation Industry. The foremost continuing study of equipment and human factor performance was started during
World War II. Focus was targeted on [eradicating] accidents with cockpit design and aircrew operations, concentrating on equipment, training, human performance under duress, and vigilance (Reason and Maddox, 1998). Due to numerous catastrophic in-flight tragedies, such as the Aloha Airlines flight 243 in April of 1989 where people were sucked out of the plane, there was a great human outcry for why these types of tragedies occurred. Investigators determined that flight 243 developed structural fuselage deterioration and failure due to decompression caused by rivet failure, owing to the vigilance effect. On the nineteen year old plane, one fourth of the top of the fuselage was sheared of in-flight at 2400 feet, causing passengers to be ripped out of their seats and flung into the air.

The Federal Aviation Association (FAA) held an international conference to address aging aircraft in June of the same year (1989), and the conclusion of the conference was noted, “The more we look at problems in maintenance operation, and particularly those of aging aircraft, the more we saw human factor as some part of the problem (Congressman James Oberstar, pg. 3, 1989). The process of inspecting rivets is monotonous, repetitious, exhausting work susceptible to human error. How do we ensure that the right information is finding its way to the right people at the right time? How do we know whether training or inspectors and mechanics are all it needs to be? These questions are not easy to answer; we are dealing with human beings who don’t perform according to mathematical models. Airline mechanics require certification by the FAA and must have a high school diploma. Most mechanics learn their skills in a FAA-certified Aviation Maintenance Technical school. A few mechanics are trained on the job by experienced mechanics, and their work must be supervised and documented by certified mechanics until they have FAA certification. The FAA requires recent work experience to keep the certification valid. Applicants must have at least 1,000 hours of work experience in the prior 24 months or take a refresher course (Hawkins, 1987). In the workplace, the Aviation Maintenance Technician (AMT) must be productive on new equipment as quickly as possible. New aircraft technology is introduced frequently, aircraft are constantly modified. Selecting the proper training methods and developing effective training material assumes a heightened level of importance in today’s aviation maintenance environment. Training and management require the ability to assess employee needs, evaluate personality

characteristics develop performance requirements that are challenging, while not beyond each person’s capabilities, and assess performance. Training should be considered and integral part of good aviation maintenance management. Practice is a proactive activity when incorporated with training (Chandler, Chapter7, and pg. 4). In aviation, accidents occur in a sequence of mistakes made, like a domino effect. Stress pushes the first domino into the rest, causing the effect. Whatever particular job a person is performing, they must take steps to avoid undue stress. Aviation maintenance is stressful because aircraft make money flying instead of being tended to in a hanger. There is enormous stress in finishing airplane maintenance within a short timeframe and getting the aircraft functional to avoid flight delays and cancellations. There are many things to be careful about, such as using the correct tools, installing the correct parts, and working in dark, tight spaces. Stress management is an important skill for maintenance personnel to hone so that they can adequately cope with stress and prevent it from overwhelming their ability to properly work (Burnette, Chapter 3, and p. 36). Aviation maintenance managers realize that a big part of their job responsibilities entail public safety. The biggest anxiety of maintenance supervisors, technicians, or inspectors is that an error, once committed, will stay unrevealed or uncovered, until an accident occurs. Improper repairs will cause breakdowns which will increase equipment failure and accidents. Some human error can be so frequent that they become the accepted practice. For example, a maintenance worker may have got into the habit of omitting final checks during routine maintenance procedures. Other human errors may only occur during exceptional circumstances such as a misdiagnosis of a routine failure. An example is a blown fuse on an electrical system

where the AMT switches out a component instead of consulting his electric flowchart which may not correct the problem. Vigilance tasks are types of tasks where a user must maintain attention on the task while waiting for an uncommon, unpredictable event, such as an AMT inspector, inspecting rivets for stress or corrosion effects. Failures of both airframe and engine inspections have highlighted the potential impact of human limitations on inspections system performance. A number of visual and Non-Destructive Inspections (NDI) techniques require the inspector to work continuously on repetitive tasks for extended periods. Examples are fluorescent penetrant inspections of engine rotor blades, eddy current inspections of large batches of wheel bolts, and magnetic particle inspections of landing gear components. Such tasks typically occur on all shifts and can involve inspections at low periods of the human circadian rhythms. Inspectors may be subject to the effects of cumulative fatigue from overtime and shift work. The functions of search and decision are the most error prone, although for much of the inspections, especially NDI, set up can cause its own unique errors (Murgatroyd, et al., 1994). Inspection tasks with Vigilance-like effect are performed at times when attention depletion or (decrements) would be expected.
Folk (2002), Fletcher and Dawson (1998) and French and Morris (2003) all give advice on avoiding cumulative fatigue states, with work rest schedules. Maintenance and inspection errors are implicated in 12% of major air accidents. However, maintenance error costs not just lives, but money too. A short list of cost factors associated with maintenance errors are: 1) Average cost of a flight engine shutdown = $500,000;
2) Average cost of a flight cancellation = $50,000; and 3) Average cost of a return to gate = $15,000. The Airline Transportation Association estimates that ground damage costs are $850

million per year. The average ground damage incident cost is $70,000. One airline estimates between $75-$100 million per year on human error (nationaltransportationlibrary- integratedtrisoline.bts.gov/).

Discussion Human error is inevitable. Reducing accidents and minimizing the consequences of accidents that do occur is best achieved by learning from errors, rather than by attributing blame. Feeding information from accidents, error and near misses into design solutions and management systems can drastically reduce the chances of future accidents. Studying human error can be a very powerful tool for preventing disasters.

References
Burnette, J.T, (1989) pg.1-5. Chapter 3: Workplace Safety
Chandler, T.N, (2003) pg.1-7 Chapter 7: Training
Department of transportation cost of aviation http://www.bts.gov/ (2010):
Fletcher, A. & Dawson, D. (2001). Field based validations of a work related fatigue model based on hours of work. Transportation Research, Part F4, 75-88.
Hawkins, F. H. (1987). Human factors in flight
Maddox, M.E, (1989).pg. 1-3 Chapter 1: Human Factors
Murgatroyd, R. A., Worrall, G. M., & Waites (1994). A study of human factors influencing the reliability of aircraft inspection. AEA Technology, AEA/TSD/0173
Reason and Maddox, ME, pg. 1-11 Chapter 14: Human Error
Sanders, M. S., & McCormick, E. J. (1987). Human factors in engineering and design, library.erau.edu/worldwide/find/online-full-text/hfami.htm –