Essay: Aviation maintenance

“When you get it right mighty beasts fly up into the sky. When you get it wrong people die.”-Roger Bacon. Aviation safety relies greatly on maintenance. When it is not done properly, it sum up to the majority of the aviation incidents and accidents. Some examples of maintenance errors are incorrect installation of parts, missing parts, important checks not being done. As a comparison to the many other threats to aviation safety like weather conditions, hijacking and pilot errors, just to mention a few, the mistakes during maintenance are more difficult to detect. Most often these mistakes are present but difficult to see and affect the safe operation of aircraft for a long period of time before being discovered.
Aviation maintenance technician (AMT) have to deal with a wide range of human factors which some are unique within the aviation maintenance industry. They often work odd hours like at night or early morning and in unusual environment such as confined spaces, on high up platforms, and in diverse temperature, humidity conditions. The work may be physically demanding, as well as it requires paying attention to details. Due to the nature of the maintenance responsibilities, AMTs mostly spend their time preparing for a task than actually undertaking it. Proper documentation of all maintenance work is the key element and AMTs normally spend a lot of time on updating the maintenance logs as well.
1.2 Human factors
Human factors (also known as Ergonomics) focuses on human beings and their interaction with products, equipment, facilities, procedures and environments used in the work and everyday living. The emphasis is on human beings and how the design of things people use and the environment in which they use these things to better match the capabilities, limitations and needs of the people.
1.2.1 Objectives of human factors
Human factors has two major objectives. The first one is to increase the efficiency and effectiveness with which work and other activities are carried out. This include increase suitability of use, reduce errors, and improve productivity. The second objectives is to encourage certain beneficial human values such as improved safety, reduction in stress and fatigue, widen comfort, magnify ease of use, elevate job satisfaction and boost up the quality of life.
It may seems an unattainable task to manage all these diverse factors but as Chapanis points out, only a few of the objectives are generally of great importance in a specific application and the objectives are usually correlated. For example, a product that is the results of human factors technology is usually not only safer, but also easier to use which results in less fatigue and stress and is more satisfying to the user.
1.2.3 Human factors history
It could be said that human factors started when early humans first fabricated simple tools. Such a claim, however, might be a little audacious. The development of the human factors field has been closely connected with developments in technology and as such had its commencement in the industrial revolutions of the late 1800s and early 1900s. It was during the early 1900s, for example, that Frank and Lillian Gilberth began their work in motion study and shop management. The Gilbreths’ work can be considered as one of the precursor to what is now called human factors. Their work included the study of skilled performance and fatigue and the design of the workstations and equipment for the handicapped. Their analysis of hospital surgical teams, for example, engendered in a procedure used today; a surgeon obtains an instrument by calling for it and extending his or her hand to a nurse who places the instrument in the proper orientation. Preceding to the Gilbreths’ work, surgeons picked up their own instruments from a tray. The Gilbreths found that with the old technique surgeons spent as much time looking for instruments as they did looking at the patient.
Despite the early contributions of people such as Gilbreths, the idea of adapting equipment and procedures to people was not harness. Behavioral scientists through World War II concluded that, even with the best selection and training, the operation of some of the complex equipment still exceeded the capabilities of the people who had to operate it. It was time to reconsider fitting the equipment to the person. Until 1960s, human factors in the United States was mainly focus in the military-industrial complex. With the race for space on, human factors quickly became a major factor in the space program and human factors in the United States proliferate beyond military and space applications. Human Factors groups could be found in many companies from computers to pharmaceutical, automobiles and other consumer products. Industry began to realize the importance and contribution of the human factors to the design of both workplace and the products manufactured there.
The computer revolution throw human factors into the public eye. Talk of ergonomically design computer equipment, user-friendly software, and human factor in the office appear to be part and parcel of almost any magazine or newspapers article involving computers and people. New control devices, information presentation via computer screen, and the impact of new technology on people are all areas where the human factors are helping.
The 1980s was, unfortunately also a decade impair by tragic, large-scale technological catastrophes. The incident at the Three Mile Island nuclear power station in 1979 set the stage for the 1980s. Although no lives were lost and the property damage was confined to the reactor itself, the incident came very close to resulting in a nuclear meltdown. The 1980s would not be so lucky. On December 4, 1984, a leak of methyl isocyanate (MIC) at the Union Carbide Pesticide plant in Bhopal, India took the lives of nearly 4000 people and injured another 200 000. Two years later in 1986, an explosion and fire at the Chernobyl nuclear power station in the Soviet Union resulted in more than 300 dead, widespread human exposure to harmful radiation, and millions of acres of radioactive contaminations. Three years later, 1989 an explosion ripped through a Phillips Petroleum plastics plant in Texas, United States. The blast was equivalent in force to 10tons of TNT. It killed 23 people, injured another 100 workers and resulted in the largest single U.S. business insurance loss in history ($1.5 billion). Meshkati in 1989 to 1991 analyze several of these disasters and his founding showed that inadequate attention to human factors considerations was a significant factor to each disaster he studied.
Plans for building a permanent space station required a huge involvement of human factors. Computers, mobile phones, electronics and its application to just about everything will keep a lot of human factors busy for a long time. Other development should also increase the demand for the human factors like biomechanics, medical industries and drones. The U.S. Occupational Safety and Health Administration (OSHA) formulated ergonomics regulations for general industry. A law passed by the U.S. Congress in 1988 ordered the Federal Aviation Administration (FAA) to expand its human factors research efforts to improve aviation safety. Two other areas where human factors are expanding are in the medical devices and in the design of products and facilities for the elderly.
1.3 Aircraft Maintenance Industry
1.3.1 MRO
Aircraft maintenance industry also known as Maintenance, Repair and Overhaul (MRO) may be defined as ‘All actions which have the objective of retaining or restoring an item in or to a state in which it can perform its required function. The actions include the combination of all technical and corresponding administrative, managerial and supervision actions.’
MROs providers play a vital role in assisting the world’s airline fleets. It is estimated that the global market is worth up to $50 billion. MRO providers exist all around the world, with the majority of the market shares concentrated in North America (35%), Western Europe (26%) and Asia Pacific (17%). Most of the world’s top 10 MRO providers are headquartered in these regions. MRO Providers can be classified into four groups namely; in-house (e.g. Qantas Engineering), Independent Third party (E.g. ST Aerospace), Airline third party (e.g. Iberia Maintenance), Original Equipment Manufacturers (E.g. Honeywell).
1.3.2 Task of MRO
(1) Configuration Management and Maintenance Engineering
Configuration management (CM) is a system engineering process for establishing and maintaining consistency of a product’s performance, functional and physical attributes with its requirements, design and operational information throughout its life. It regroup preventive maintenance, corrective maintenance, condition monitoring, predictive maintenance and fault diagnosis.
Every airlines has a maintenance program for each types of airplanes it operates. The program are developed jointly with the manufacturers of the equipment and must be approved by the FAA. Each involves a series of increasingly complex inspection and maintenance steps fit to an aircraft’s flying time, calendar time, number of landings and take offs. With each steps, maintenance personnel explore the aircraft, taking apart more and more components for a closer look. Among the many inspection and maintenance procedures, a typical program involves: a visual inspection ‘walk around’ of an aircraft’s exterior, several times each day to look for worn tires, leaks, dents, cracks and other surface damages. An inspection every 3-5 days of the aircraft’s landing gear, control surfaces such as flaps and rudder, oxygen systems, fluid levels, lighting and auxiliary power system. An inspection every six to nine months of all the above plus internal control system, hydraulic systems and cockpit and cabin emergency equipment. A check every 12-17 months, during which aircraft are opened up extensively so inspectors can use sophisticated devices to look for wear, corrosion and cracks invisible to human eyes. A major check every 3-5 years in which aircraft essentials taken apart and put back together again, with landing gear and many other components replaced.
In between these schedules maintenance checks, computer onboard the aircraft monitor the performance of aircraft systems and recode such things as abnormal temperature, fuel and oil consumption. In modern airplanes, this information is transmitted in real time to ground stations while the airplane is in flight. All U.S. airlines have extensive maintenance facilities and do most of their own maintenance work. Some tasks, however are contracted to independent parties, both domestic and foreign, since many airlines now operate globally. All of the repair stations the airlines use must be FAA-approved and no matter where the work is done, the airline itself retains the ultimate responsibility for the quality of the work.
(2) Maintenance Planning and Scheduling
It consist of performing long-range planning for inventory, human resources, capacity and visit planning. Provide notice to materials planning for special programs, conducts short planning, ensuring manpower, parts, hangar facilities availability and tools and equipment availability. It also have to establish capabilities for non-routine work, create an efficient sequence of work, schedule work cards and forecasting of inventory.
(3) Quality Assurance
It involves performing monitoring, analysis of causes of non-quality throughout organization. They have to audit the configuration model for accuracy and completeness, audit maintenance review board findings, changes in schedule maintenance program and auditing part number in part catalogue to engineering documents to validate parts catalogue number to be approved for use. The airlines also have the ultimate responsibility for all of the parts they buy. To ensure that all parts meet original manufacturer specifications, airlines have vigorous purchasing procedures and quality control programs that test parts when they are delivered.
(4) Post visit Analysis and Support
It consist of conducting analysis of planned versus actual work package for manpower and materials. They have to identify and analyze unscheduled work, perform closure on material management open items, execute billings and measure performance and trends. Performance and trends of engine vibration, heat to airplane delays.
1.3.3 Aircraft Maintenance Staffs
The aircraft maintenance profession is as old as aviation itself. The training of workers traditionally would lie in the hand of the aircraft owner through an apprenticeship scheme, as this is a field that largely relies on skill base. At the beginning aircraft maintenance focused on mechanical systems and the engine as the aircraft was made up of a structure, control mechanism and the engine. However with new aircraft technology, aircraft maintenance engineering become more complex due to extra equipment being installed into aircrafts such as; auto pilot, navigational systems and lately in-flight entertainment and so forth. The aviation industry has seen a number of insurrection mainly driven by technology which brought the aspect of safety in the industry. Safety in this context does not limit itself to safety of the crew and passengers onboard the aircraft, but also safety of those on the ground as well.
Due to this necessity of ensuring safety in this particular field, government regulations became a necessity and therefore have a critical role in the safety of aviation maintenance. The licensing began in 1909 and by the year 1919 the first international licensing standard were established as Annex E of the Paris Convention. The early standards of licensing were manly for the air crew and was based on medical fitness as well as experience. The first personnel licensing standards were applied by the International Civil Aviation Organization (ICAO) in 1948. This licensing was structured to ensure control through a metrics comprising; categories, groups and rating. Each maintenance engineering license is different as a rating is applied on a license depending on the training the engineer has received on a specific aircraft and part. ICAO is responsible for establishing the licensing standards but enforcement of the standards in the responsibility of the government of the state of any given country. Today the training of aircraft maintenance personnel make certain that safe practices are incorporated accompanied with Human Factors so as to make sure that this safety culture in maintained.
There are basically two main bodies under which workers get certification namely the FAA and the European Aviation Safety Agency (EASA). Mechanic certification under FAA guidelines requires the mechanic have at least 18 months of practical experience with either power plants or airframes, or 30 months of practical experience working on both at the same time. As an alternative to this experience requirement, a candidate could graduate from an FAA-Approved Aviation Maintenance Technician School or have military work experience supervised by a certified aviation mechanic. Following completion of one of these requirements, the FAA imposes additional testing requirements be met by the applicant. Aircraft Maintenance Technicians (AMTs) or Mechanic Airframe & Power plant (A&P) refers to an individual who holds a mechanic certificate issued by FAA and his job is to inspect and perform or supervise maintenance, preventive maintenance, and alteration of aircraft and aircraft systems.
Mechanics seeking certification from EASA will have to comply with part-66 Certifying Staff of the EASA. Part 66 is based on the older Joint Aviation Requirements (JAR) system and includes 3 levels of authorization: Category A (Line Maintenance Mechanic): This permits the holder to issue certificates of release to service following minor scheduled line maintenance and simple defect rectification within the limits of tasks specifically endorsed on the authorization. Category B1(Mechanical) and/or B2 (Avionics) (Line Maintenance Technician): B1 category permits the holder to issue certificates of release to service following maintenance, including aircraft structure, power plant and mechanical and electrical systems. Replacement of avionic line replaceable units, requiring simple tests to prove their serviceability, are also be included in the privileges. Category B2 aircraft maintenance license shall permit the holder to issue certificates of release to service following maintenance on avionic and electrical systems. Category C (Base Maintenance Engineer): permit the holder to issue certificates of release to service following base maintenance on aircraft. The privileges apply to the aircraft in its entirety in a Part-145 organization”).
To become an engineer one will attend a certified school that is registered under the ‘National Airworthiness Authority’ of the country they are seeking to work for. Under the course they will basically learn all that is required for maintaining a typical aircraft. Once the theoretical work is complete, the student will then go through an apprenticeship which range from 2 to 4 years, depending on the institution requirements. Once the theory and practical part of the source is complete, the student will receive a License without Type Rating (LWTR). An engineer can now decide whether to gain further certification or seek employment just as a general maintenance engineer who is not certified in a specific maintenance type.
A significant difference between the US and the European systems is that in the US aircraft maintenance technicians (Part 65 Airframe and Powerplant Mechanics) are permitted to work under their own certificates and approve their own work for return to service. European Part 66 certificate holders are required to perform their functions under the aegis of a Part 145 organization for Transport Category and Large (MTOM>5700 kg) Airplanes. The part 145 organization in the EASA system has the authority to approve for return to service. Many non-European countries have been moving toward the European approach, most notably Canada (Part 571 of the Canadian Aviation Regulations).
In Canada the equivalent of an FAA “A&P with an Inspection authorization” is “aircraft maintenance engineer” (AME). The British equivalent of an FAA “A&P” is aircraft maintenance engineer and the British equivalent of an FAA “A&P with an inspection authorization” is “licensed aircraft maintenance engineer” (L-AME) or “AME – licensed with type rating” (AME-LWTR). The United Kingdom (UK) system also defines aircraft type endorsements and differentiations for the level and scope of work including “line maintenance”, “overhaul” and “base maintenance”. In Australia and New Zealand the equivalent of an FAA “A&P” is “aircraft maintenance engineer” and the equivalent of an FAA “A&P with an inspection authorization” is “licensed aircraft maintenance engineer”.
1.3.4 Regulatory Requirements
The FAA concurs with European Authorities in that human factors training related to maintenance practices would provide an additional margin of safety to the repair industry. EASA Part-145 and 14 Code of Federal Regulations (CFR) part 145 regulations require that personnel involved in any maintenance, management and/or quality audits, must have an understanding of the application of human factors and human performance capabilities. Part 145 approved maintenance organizations are required to have completed the initial training by 28th September 2006. Maintenance Human Factors (MHF) training examines the importance of human factors to aircraft maintenance engineering. It is essential to all personnel operating in an aircraft maintenance and engineering environment. The aim of MHF training is to increase safety, quality and efficiency in aircraft maintenance operations by reducing human error and its impact on maintenance activities.
The organization shall establish and control the competence of personnel involved in any maintenance, management and/or quality audits in accordance with a procedure and to a standard agreed by the competent authority. In addition to the necessary expertise related to the job function, competence must include an understanding of the application of human factors and human performance issues appropriate to that person’s function in the organization. “Human factors” means principles which apply to aeronautical design, certification, training, operations and maintenance and which seek safe interface between the human and other system components by proper consideration of human performance. “Human performance” means human capabilities and limitations which have an impact on the safety and efficiency of aeronautical operations.
1.4 Statement of the Problem
Safety is crucial in the airline industry. In the past, most research were being focus on the decrease of mechanical failures and pilots errors. Recently, researchers are devoting more attention to the contribution of maintenance to accidents and incidents. Aviation inspection and maintenance tasks are part of an intricate organization, where individuals perform a wide range of tasks in an environment with time pressure, sparse feedback and sometimes uncomfortable ambient conditions. These situational characteristics combined with genetic human tendency to err, results in various forms of errors. The most severe will results in catastrophe with loss of life. The United States statistics for aviation accidents indicate that 80% of them are the results of human factor with 50% due to human factors troubles. While errors resulting in accidents are most dominant, maintenance and inspection errors have other important consequences such as: air turn-back, delays, gate returns or diversion to alternate airports which affect greatly productivity and efficiency of airlines operations and inconvenience to the flying public. Statistics shows that 50% of flight delays in the U.S. are due to maintenance errors. The role of the human in an aviation system is complex; thus the nature of human errors, from mental to physical, in aviation accidents varies widely. Mental or cognitive errors can include improper judgment or decision-making, while physical errors may stem from motor skill deficiencies or equipment design. A combination of physical and mental processes may influence other kinds of errors, such as those involving communication, perception, or alertness.
Chapter 2?? Human Factors in Aviation Maintenance Industry
2.1 Human Factors in Aircraft Maintenance
Due to a wave of maintenance related aviation incidents and accidents in the late 1980s and early 1990s, Transport Canada together with the aviation industry identified 12 human factors, named the ‘Dirty Dozen’ which were human factors elements that deteriorate people’s ability to perform safely and efficiently which may result in maintenance errors. The Dirty Dozen is a concept developed by Gordon Dupont in 1993 while he was working for Transport Canada and formed part of an elementary training program for Human Performance in Maintenance. It has since become the foundation of human factors in maintenance training courses worldwide. 19994, dirty dozen posters were established which provided guidance and information to maintenance personnel all over the world to identify and prevent these issues. Safety nets were also introduced so that the appropriate measures are done to prevent those human errors.
Table 2. 1 The Dirty Dozen
1. Lack of communication
The exchange of information that conveys meaning between two or more people. Lack of communication often leads to misunderstandings and the results could be catastrophic.
2. Complacency
Self-satisfaction accompanied by a loss of awareness of the dangers. This often happens when doing familiar, repetitive work.
3. Lack of knowledge
Insufficient experience or training in the task-at-hand. It is easy to see how lack of knowledge could lead to an error or an accident. Often lack of assertiveness plays a part because people do not like to admit they do not know something.
4. Distraction
One’s attention is drawn away; mental or emotional confusion or disturbance occurs. When working among many people, with frequent work interruptions, or when coping with stress, it is easy to become distracted.
5. Lack of teamwork
Failing to work together to achieve a common goal. Lack of teamwork creates an unhealthy environment in terms of personal dissatisfaction and group disconnect.
6. Fatigue
Weariness from labor or exertion, nervous exhaustion, temporary loss of power to respond. Shift work can have an enormous physical impact.
7. Lack of resources
Failing to use or acquire the appropriate tools, equipment, information, and procedures for the task-at-hand. Lack of resources or misusing resources has been linked to many accidents or incidents.
8. Pressure
Pushing for something, in spite of opposing odds, or creating a sense of urgency or haste. This factor is most prevalent when deadlines approach or when trying to meet a tight schedule.
9. Lack of assertiveness
Failing to behave in a self-confident manner. Lack of assertiveness has been identified as a link in the chain of events for many accidents.
10. Stress
Mental, emotional, or physical tension, strain, or distress. Stress is not inherently good or bad; how one handles it determines its impact on the individual. Stress is very difficult to measure objectively.
11. Lack of awareness
Failing to be alert or vigilant in observing. Lack of awareness of the work situation or your surroundings often results in error or injury to yourself or others.
12. Norms
Unwritten and, often, unspoken rules about how work is done. Always work according to the instructions. If norm are actually a better way to do things, change the instructions so norms become part of the approved procedures.
The aviation maintenance personnel work in highly sophisticated aircraft’s with complex in-built system. Hence they need to be trained on upgraded technologies and new systems in order to provide an error free maintenance. The maintenance personnel should be trained in such way to be able to repair, analyze and certify the systems according to the standards of the Aircraft manufacturers and the Aviation authorities. However these rapid improvements in technology and complexity of the systems have been helpful in maintenance operations, they also present new possibilities of human errors.
A survey designed to discern safety issues in maintenance stressing on human factors were hand out to Licensed Aircraft Maintenance Engineers (LAME) in Australia and the following were provided by the Australian Transport Safety Bureau. The re-assembly and installation are the areas where errors occur irrespective of who does the job and these are the major error prone activities of aviation maintenance. Other factors include foreign object damage, complex maintenance related task, time pressure for delivering the aircraft, fatigue of maintenance crew, maintenance procedures not followed accordingly and usage of outdated maintenance manual.
Table 2. 2 Outcome of Safety Occurrences
Outcome of Safety Occurrences Airline Non-airline
System operated unsafely during maintenance 18% 7%
Towing event 9% 3%
Incomplete installation, all parts present 8% 9%
Person contacted hazard 7% 9%
Vehicle or equipment contacted aircraft 7% 1%
Incorrect assembly or orientation 6% 11%
Material left in aircraft 4% 5%
Part damaged during repair 4% 2%
Panel od cap not closed 3% 3%
Incorrect equipment/part installed 3% 4%
Part not installed 3% 6%
Required servicing not performed 3% 4%
Degradation not found 3% 5%
others 24% 31%
2.2 Unsafe acts
Unsafe acts in aviation maintenance can be classified into two categories: errors and violations. In general errors represent unintentional mistakes that we make all the times as human. An unintentional error is an unintentional wandering or deviation from accuracy. This can include an error in action like a slip, opinion or judgment caused by poor reasoning, carelessness, or insufficient knowledge. For example an AMT reads the torque values from a job card and unintentionally transpose the values 43 to 34. He or she did not mean to make that error but unknowingly did it. Another example is selecting the wrong job card to conduct a specific job. Violation on the other hand refer to the intentional disregard for the rules and regulations that governs safe maintenance practice. Typically, the violator intends only to ignore the rule, but does not intend any harmful result. An example is when an experience AMT is doing a check and skip some steps in the procedures because he is in a hurry to deliver the aircraft and know that the probability of something going wrong in these missing steps is quite low but still possible.
Errors can be further regroup into three categories namely decision errors, skill-based errors and perceptual errors. Decision errors represent conscious decisions or choices made by an individual that are carried out as intended, but prove inadequate for the situation at hand. These so-called “thinking” errors generally arise from a lack of knowledge, information, or experience. In contrast, skill-based behavior within the context of aviation is best described as ‘automatic’ behavior or ‘reflex’ that occur without significant conscious thought. As a result, these skill-based actions are particularly vulnerable to failures of attention and/or memory as well as simple technique failures. For example most people do not have to think about how to use a screw driver, typing on a keyboard or riding a bicycle, they just do it. These “skills” are highly practiced and over time become quite routine and seemingly automatic. Finally, perceptual errors occur when sensory input is altered by physical surroundings or degraded or ‘unusual,’ as is often the case when performing at night.
Violation can be also broken down into routine violation and exceptional violations. Routine violations, tend to be habitual by nature and are often tolerated by the governing authority and commonly referred to as ‘bending the rules’. Violations often occur with the full knowledge and implicit approval of management since most often, violations occur because the “legal” way of doing things doesn’t work or is inefficient. An example is when AMT who routinely works on an aircraft without proper personal protective equipment (PPE). While it is certainly against the rule, some other people may also follow that same unsafe act. The second type, exceptional violations, appear as isolated departures from authority not necessarily characteristic of an individual’s behavior nor condoned by management. . For example, signing off a maintenance sheet without performing the maintenance or inspecting the work would typically be considered an exceptional violation
2.3 Accidents attributed to Maintenance Errors
2.3.1 Robinson R22 ZK-HVN
Date: 26 August 2005
Location: Murchison, New Zealand
Aircraft: Robinson R22 Helicopter
Accident type: Maintenance error due to incorrect assembly
A safety investigation by the Civil Aviation Authority (CAA) has concluded that the failure of an incorrectly assembled tail rotor drive shaft had caused that helicopter to crash inverted in a paddock, killing the pilot and seriously injuring the passenger. The safety investigation concluded that: the certifying licensed maintenance engineer did not directly supervise the unlicensed personnel as he was required to do during the final assembly of the tail rotor drive shaft. Without supervision, the aft coupling on the tail rotor drive shaft was assembled incorrectly. The certifying licensed aircraft maintenance engineer should not have signed the release to service statement without ensuring that the duplicate inspection had been completed and correctly certified as required by the Civil Aviation Rules, and as adequate physical check had been carried out by the second person. The Chief Executive Officer (CEO) of the maintenance organization had been made aware of the requirements for direct supervision and should have halted the critical maintenance tasks until the certifying licensed aircraft maintenance engineer was present to directly supervise the maintenance being performed.
2.3.2 Air Transat Flight TSC236
Date: 24 August 2001
Location: Terceira Airport, Azores
Aircraft: Airbus A330-243
Accident type: Maintenance error
It was a scheduled flight from Toronto, Canada to Lisbon, Portugal where a fuel leak in the Number 2 (right) Engine began three hours 46 minutes into the flight that was not detected by the flight crew. Due to a developing fuel leak began, the flight crew initiated a diversion from the planned route for a landing at Lajes Airport on Terceira Island in the Azores. Approximately 150 nautical miles from Lajes, Airport, the crew notified air traffic control that the right engine had flamed out. When the aircraft was about 65 nautical miles from the Lajes airport and at an altitude of about 34,500 feet, the crew reported that the left engine had also flamed out, and that a ditching at sea was possible.
Assisted by radar vectors from Lajes air traffic control, the crew carried out an all-engine out visual approach and landing at night, in good visual weather conditions. The aircraft landed on runway 33 at the Lajes Airport at 06:45 Coordinated Universal Time (UTC). An emergency evacuation was conducted. Sixteen passengers and two cabin-crew members received injuries during the emergency evacuation. The aircraft suffered structural damage to the fuselage and to the main landing gear. The accident investigators determined that the fuel leak was caused by fuel line cracking that resulted from interference between the fuel line and a hydraulic line on the right engine. The interference was caused by an incomplete service bulletin incorporation creating a mismatch between the fuel and hydraulic lines during replacement of the right engine.
2.4 Accident Causation Method
2.4.1 Heinrich’s Domino Theory
In 1931, the late H.W. Heinrich presented a set of theorems known as ‘the Axioms of Industrial Safety’. The first axiom dealt accident causation, stating that ‘the occurrence of an injury invariably results from a complicated sequence of factors, the last one of which being the accident itself’. Alongside, he developed a model known as the ‘Domino Theory’ as this accident sequence was linked to a row of dominoes knocking each other down in a row. The sequence is: injury, caused by an Accident, due to an unsafe act and/or mechanical or physical hazard, due to the fault of the person, caused by their ancestry and social environment. The accident is avoided, according to Heinrich by removing any one of the dominoes, normally the middle one or unsafe act. This theory provide the cornerstone for accident prevention measures aimed at preventing unsafe acts or unsafe conditions.
2.4.2 SHELL model
The SHELL model is a conceptual model of human factors and its relationship between aviation system resources/environment and the human component in the aviation system. The SHELL model was first developed by Edwards in 1972 and later modified into a building block’ structured by Hawkins in 1984. SHELL is an acronym which stand for Software, Hardware, Environment and Liveware. It focus on human beings and human interaction with the other components of the aviation systems.
‘ Software – the rules, procedures, written documents etc., which are part of the standard operating procedures.
‘ Hardware – the Air Traffic Control suites, their configuration, controls and surfaces, displays and functional systems.
‘ Environment – the situation in which the L-H-S system must function, the social and economic climate as well as the natural environment.
‘ Liveware – the human beings – the controller with other controllers, flight crews, engineers and maintenance personnel, management and administration people – within in the system.
2.4.3 PEAR model
The PEAR model is a simple framework for analyzing human factors mainly in aviation maintenance. PEAR is an acronym for People, Environment, Actions and Resources. These four components comprise the essence of what we are typically concern about in the human factors world. While ‘People’ components is only one of the four block in the Pear model, similar to the SHELL model it is the center of the entire model. The science of Human factors concerns itself primarily with people and how they interact with each other and the world around them.
Table 2. 3 PEAR model
People- Who we are
Physical factors Sex, age, physical characteristics, strength, sensory limitation
Physiological factors Nutritional factors, health, lifestyle, fatigue, drugs, physical limitations
Psychological factors Workload, experience, knowledge, training, attitude, mental r emotional state
Psychosocial factors Interpersonal conflicts, personal loss, financial hardship
Environment- Where do we work?
Physical Weather, location inside/outside, workspace, lightings, noise, safety, humidity
Organizational Personnel, supervision, shift, union-management relations, pressure, crew structures, size of company, profitability, moral culture.
Actions- What do we do?
Steps, performance criteria, number of people involved, communication (oral, visual, written)
Requirements Information and control, knowledge, skill, attitude, certification, inspection
Resources- What and whom do we use to do our job?
Paper Procedures/work card, Manuals/bulletins/FARs, paperwork/signoffs, fixtures,
Equipment Test equipment, hand/power tools, machine tools, computers, ground handling equipment, materials, task lightings, manpower, other people, and training.
Several methods like checklist evaluation, field observation, formal usability testing, incident investigation, link analysis, questionnaires and opinionnaires, task analysis, Walkthrough Evaluation are used to identify human factors problems and to embed user capabilities and limitations into systems and products to accomplish one or more of the following tasks: Identify user characteristics, Identify task requirements, Evaluate jobs, tasks, or products
2.4.4 Human Factors Analysis and Classification System (HFACS)
The Human Factors Analysis and Classification System (HFACS) was developed by Dr. Scott Shappell and Dr. Doug Wiegmann. It is a broad human error framework that was originally used by the US Air Force to investigate and analyze human factors aspects of aviation. HFACS is heavily based upon James Reason’s Swiss cheese model (Reason 1990). The HFACS framework provides a tool to assist in the investigation process and target training and prevention efforts. Investigators are able to systematically identify active and latent failures within an organization that culminated in an accident. The goal of HFACS is not to attribute blame; it is to understand the underlying causal factors that lead to an accident.
The HFACS framework describes human error at each of four levels of failure: unsafe acts of operators, preconditions for unsafe acts, unsafe supervision and organizational influences. Within each level of HFACS, causal categories were developed that identify the active and latent failures that occur. In theory, at least one failure will occur at each level leading to an adverse event. If at any time leading up to the adverse event, one of the failures is corrected, the adverse event will be prevented.
Figure 2. 7 Four Levels of HFACS
2.4.5 Maintenance Error Decision Aid (MEDA)
Boeing, in collaboration with British Airways, Continental Airlines the International Association of Machinists, and the FAA developed a process for maintenance-error-caused events in order to determine what affected errors so as to take appropriate actions to reduce or eliminate probability of similar future errors. It developed into a project to provide maintenance organizations with a standardized process for analyzing contributing factors to errors and developing possible corrective actions. The process is called the Maintenance Error Decision Aid (MEDA). MEDA is intended to help airlines shift from blaming maintenance personnel for making errors to systematically investigating and understanding contributing causes. MEDA is based on the philosophy that errors result from a series of related factors. In maintenance practices, those factors typically include misleading or incorrect information, design issues, inadequate communication, and time pressure. Boeing maintenance human factors experts worked with industry maintenance personnel to develop the MEDA process. Once developed, the process was tested with eight operators under a contract with the FAA. MEDA model is based on the probabilistic relationship between the contributing factors, errors (system failures) and events. The MEDA process offers maintenance organizations an event investigation process. MEDA can serve as the reactive hazard identification process that will be necessary when a Safety Management System is required by regulation.
2.4.6 Safety Management Systems (SMS)
A safety Management System (SMS) is an integral part of management and work practices, beliefs and procedures for monitoring, supporting and improving the quality of safety aspect and human performance in an organization. SMS help organization recognize potential errors and set strong defense to prevent these errors from causing injuries or accidents. SMS focus on organizational safety rather than the conventional employee safety and health workplace concern. An SMS is basically a quality management approach to control risk. An effective SMS helps organizations become proactive in their approach to safety by actively identifying risks and hazards, and supporting the implementation of appropriate solutions. A key aspect of this new view of safety is the recognition of human limitations. Every employee in every department contributes to the safety awareness of the organization. A successful SMS provides a process for managing risk and reducing human error more efficiently with the collective efforts of all members, thus having a positive financial impact on corporate profitability.
Safety is no longer the responsibility of just the dedicated safety professionals who in the past led the charge for safety improvements. By clearly placing responsibility for safety performance in the hands of all of the operating divisions, safety becomes everyone’s business. Only then is it possible to create a true safety culture in an organization. Clear authorities, responsibilities and accountabilities for safety, at all levels within the organization needs to be included in an effective safety management system. This includes the following: Senior management commitment to safety as a core value, Safety policy, Discipline policy, Hazard identification and safety risk management, Establishing accident, incident, hazard reporting and investigation Programs, Safety orientation and recurrent training, Maintain open and constant communication. SMS is also becoming a standard for the management of safety beyond aviation.
SMS is composed of four functional components: Safety Policy, Safety Risk Management, Safety Assurance and Safety Promotion. The Safety Policy Establishes senior management’s commitment to continually improve safety; defines the methods, processes, and organizational structure needed to meet safety goals. The Safety Risk Management determines the need for, and adequacy of, new or revised risk controls based on the assessment of acceptable risk. Safety Assurance evaluates the continued effectiveness of implemented risk control strategies; supports the identification of new hazards. Safety Promotion includes training, communication, and other actions to create a positive safety culture within all levels of the workforce.
Figure 2. 10 The Four SMS Components
2.4.7 Aviation Safety Reporting Systems (ASRS)
The Aviation Safety Reporting System (ASRS) is the FAA voluntary confidential reporting system that allows pilots and other airplane crew members to confidentially report near misses and close calls in the interest of improving air safety. The confidential and independent nature of the ASRS is key to its success, since reporters do not have to worry about any possible negative consequences of coming forward with safety problems. The ASRS is run by National Aeronautics and Space Administration (NASA), a neutral party, since it has no power in enforcement. The success of the system serves as a positive example that is often used as a model by other industries seeking to make improvements in safety. Its database is a public repository which serves the FAA and NASA’s needs and those of other organizations world-wide which are engaged in research and the promotion of safe flight. The ASRS collects, analyzes, and responds to voluntarily submitted aviation safety incident reports in order to lessen the likelihood of aviation accidents. ASRS data are used to: Identify deficiencies and discrepancies in the National Aviation System (NAS) so that these can be remedied by appropriate authorities. Support policy formulation and planning for, and improvements to, the NAS. Strengthen the foundation of aviation human factors safety research.
2.5 Aircraft Accidents Analysis
A study done by analyzing three different sources of data from 1999 to 2008, 769 National Transportation Safety Board (NTSB) accident reports, 3242 FAA incident reports, and 7478 FAA records of fines and other legal actions taken against airlines and associated organizations showed that maintenance-related accidents are approximately 6.5 times more likely to be fatal than accidents in general, and that when fatalities do occur, maintenance accidents result in approximately 3.6 times more fatalities on average. That analysis of accident trends indicates that this contribution to accident risk has remained mostly constant over the past decade. Analysis of incidents and FAA fines and legal actions also revealed similar trends. Also found that at least 10% of incidents involving mechanical failures such as ruptured hydraulic lines can be attributed to maintenance, suggesting that there may be issues surrounding both the design of and compliance with maintenance plans. Similarly 36% of FAA fines and legal actions involve inadequate maintenance.
The people who operate and support the aviation industry are crucial to its safety; the resourcefulness and skills of crewmembers, air traffic controllers, and mechanics help prevent countless mishaps each day. Without an understanding of human behavior factors in the operation of a system, preventive or corrective actions are impossible. This is why we have to study human factor in aviation maintenance industry. The old view about human error and aviation safety are that Human error is the cause of accidents, Human is the most unreliable component and we Improves safety by restricting human actions whereas the New views are that Human error is the effect of deeper issues, Human is necessary to create safety and we Improve safety by understanding (and leveraging) human performance.
2.6 Contributing Factors to Human Errors
Many types of human error are systematic, following certain predictable patterns; once these patterns are identified, countermeasures can be developed. Not only the interactions of people, machines, and environment influence the performance capabilities of physically fit, emotionally stable, human operators but management practices, such as labor relations and work scheduling, also affect employee stress and fatigue. While conditions that affect a person’s fitness and mental health generally influence his performance limitations, little is known about the magnitude of this relationship. For those types of human error that do not follow predictable patterns, intervention techniques and limitation methods are difficult to develop. Furthermore, any change to a complex system like aviation safety can have wide-ranging and often unpredictable effects; two solutions for that are preventing or limiting the number of errors, and compensating for errors that occur.
While preventing all human error is impossible, error rates can be reduced. In aviation, as in other fields, rules and procedures are used to limit errors by modifying or restricting human behavior through standards governing personnel qualifications, operating rules, and equipment design. An alternate approach to addressing human error assumes that errors will occur and then mitigates or nullifies them. Central to this method is an understanding of what errors occur; such information is provided by accident and incident investigations, which usually identify the human errors involved. Successful ways of compensating for known human errors entail changes to vehicles, equipment, or the environment. Modifying human behavior, even with respect to known types of human error.
The above figure provides the knowledge about the frequency of factors contributing to human errors, accidents and incidents according to the views of Management and Operational personnel. Personal Factors and communication are the main contributing factors as recognize by both management and operational personnel although management seems to be more aware of the contributing factors than the operational personnel. The personal factors can be broken down into different stressors such as Time pressure, stress, fatigue, motivation, physical characteristics, emotional states and so on. From the following table below, Time pressure is considered by both Management and Operational personnel as the most frequent contributing cause of human error. Next to time pressure, Stress and Fatigue are also mentioned as important factors, which may be related to time pressure. Most of the time a combination of those factors are the causes of the human errors which leads to incidents and accidents.