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Media Object File Maint Hum Per Seq01

  1. 1. Human Performance Maintenance Briefing Notes Human Performance and Limitations Maintenance Briefing Notes Human Performance Human Performance and Limitations I Introduction With the traffic growth and increased demands upon aircraft utilization, the pressure of maintenance operations on-time performance tends to increase. Consequently, there is at present a growing need for an enhanced awareness of the importance of human factors issues in aircraft maintenance. The safety and effectiveness of airline operations are also becoming more directly related to the performance of the people who maintain, inspect and service the aircraft fleets. The diverse nature of operations within today's complex aerospace industry gives rise to dramatically different maintenance structures. With the dynamics of aviation maintenance operations and the associated technician human factors there is a need to understand the varying effects imposed by the unique maintenance environment. The objectives of this Maintenance Briefing Note are: • To provide the reader with an enhanced human factors awareness on aircraft maintenance; • To show how human capabilities and limitations can influence task performance and safety within the maintenance environment; and, • To guide the reader towards the related prevention strategies. Page 1 of 15
  2. 2. Human Performance Maintenance Briefing Notes Human Performance and Limitations II Case Studies To enhance awareness of maintenance operations this Maintenance Briefing Note includes educational background coming with statistical data and case studies on reported maintenance events, highlighting what happened, why it happened and what can be done to avoid recurrence. II.1 The source of case studies Supplemental to the treatment of technical in-service reports by the Airbus Customer Services Technical Support, a Maintenance Event Analysis Panel (MEAP) has been put in place. The role of the MEAP is to review all in-service events classified as significant related to maintenance operations, and to conduct investigations in a broader perspective. In order to view the problem from different angles, a wide range of experts ( representing domains such as human factors, flight safety, engineering, technical data, maintenance engineering, maintenance training and some others ) are participating to regular meetings. Each significant maintenance event is investigated including considerations of potential consequences in a different context, related maintenance and troubleshooting instructions, scheduled maintenance tasks, and the environmental circumstances under which the event happened. Further to this analysis the MEAP has the authority to launch revisions to maintenance manuals and tasks, ask for further investigations or propose technical changes if so justified. In each Maintenance Briefing Note we intend to share a real in-service event related to maintenance activities, including the description of the event, possible reasons why it occurred, and recommendations on how to avoid the re-occurrence. The events investigated through the MEAP proceeding will be one source among others, for these case studies. Page 2 of 15
  3. 3. Human Performance Maintenance Briefing Notes Human Performance and Limitations III Statistical Data Human failures are often recognized as being a contributor to incidents and accidents. Technical and maintenance faults took over from CFIT as the biggest cause of fatal airliner accidents. Some authorities consider that improper maintenance is now contributing to a greater proportion of accidents than it did in the past. This is because we did a lot to reduce CFIT. Graphic 1 summarizes all the above. Number Of Accidents 4 (12%) 11 (31%) 5 (15%) 7 (21%) 7 (21%) Weather/icing Human Factors Unknown Controlled Flight Into Terrain Technical/Maintenance ( Source: Flight International – Airline Safety Review ) Graphic 1 Fatal Commercial Accidents Category / Main Causal Factor Page 3 of 15
  4. 4. Human Performance Maintenance Briefing Notes Human Performance and Limitations IV Learning more about Human Factors in Maintenance Environment The interaction between three factors affects human performance at work: the job, the individual and the organization. This means that, in a well-managed organization, taking the ideal situation: Management within the The Job is well designed to match Organization takes responsibility known strengths and limitations of for all aspects of work and work the person or team doing it. This design and encourages a good includes: work areas, the safety culture by showing environment, tools, materials, commitment and consulting the machinery, control and display workforce when making decisions. devices, management and A learning organization will take communications systems and all into account the latest thinking on technical documentation for best practice in safety and will guidance and job control. learn from accidents and near misses. The company will also select Individuals matched to the needs of the job. (Fitting the human to the job). They will have: the most suitable physique (size, build and strength), personality and intelligence fitted to the job. They will be fully competent by having the right skills, understanding, experience and training. Figure 1 “The ideal World” Page 4 of 15
  5. 5. Human Performance Maintenance Briefing Notes Human Performance and Limitations IV.1 Factors influencing the behavior of people at work However, the management has to understand the influencing factors affecting the behavior of people at work. Following are the main reasons why people do not always perform their work properly: The Environment: • Weather inconvenience, extreme temperatures, high noise levels, inadequate lightning, insufficient environment protection; • Shift work: breaks across shifts, handover; • Task characteristics: new, complex, confusing, rarely performed, requires good memory, monotonous, etc.; and, • Operational pressure: (time pressure, Customer pressure). The Individual: • Physical fatigue, synchronization (time zone, date/night shifts), medical conditions, hearing, sight; • Insufficiency of technical knowledge; and, • Communication skills, moral, attitude towards work and colleagues. The Organization: • Procedures can be missing or are out of date; • Unclear designed checklists; • Not enough tools, inappropriate equipment; • Aircraft design is not always good for maintainability; and, • Lack of spare parts and relevant material. Errors are possible in all maintenance tasks – some are more error-prone than others. Human errors are major cause of accidents and can occur in all jobs – including operations, maintenance, modification and management. Does this mean that people have become more careless, forgetful, inattentive and reckless over this period? Probably not, but it does reflect two important and widespread trends: • Aircraft components, along with most other items of equipment, have become both more sophisticated and more reliable over the past three decades; and • There is a growing appreciation that designers, manufacturers, corporate decision makers, and maintenance managers can make mistakes which, in turn, create the conditions promoting errors on the hangar floor. Page 5 of 15
  6. 6. Human Performance Maintenance Briefing Notes Human Performance and Limitations Error is a normal component of human behavior. The trouble with an error in aviation lies with the negative consequences it may generate in operational context. However, we can trap the negative consequences before they produce damage. Organizations can manage human errors by implementing re-active and pro-active measures, and strategies. V Origins of Human Error The origins of human errors are generally differentiated by whether the error was caused by the individual involved in the incident, by design features of the equipment or procedures used by the individual which compelled them to make the mistake. This focuses on determining whether the source of the human error was due to the technician, which are attributed to such factors as individual choice of inaccurate behavior, poor judgment or decisions, or generated by circumstances such as incorrect or inadequate policies/procedures, equipment, design, and tooling, working conditions, limitations or stressors. V.1 Active failures versus latent failures The main characteristic of maintenance errors is their lack of visibility. Maintenance errors can remain silent for very long time in the system before producing visible effects. Active failures Active failures are the result of unsafe acts (errors and violations) committed by those at the quot;sharp endquot; of the system. In the case of active failures, the negative outcome is almost immediate. Latent failures Latent failures are created as the result of decisions, taken at the higher echelons of the organization. Their damaging consequences can take a long time to reveal themselves, sometimes many years, only becoming evident when they combine with local triggering factors (e.g., errors, violations and local conditions) to breach the system's defenses. That is often the case for latent failures that cause or contribute to maintenance errors. Page 6 of 15
  7. 7. Human Performance Maintenance Briefing Notes Human Performance and Limitations V.2 Some local triggering factors that impact maintenance activities The aircraft engineer is the central part of the aircraft maintenance system. It is therefore very useful to be aware of the factors which affect maintenance activities. Knowledge, skills, experience: • Being unfamiliar with a failure report or aircraft type; • Lack of specific training or skills; • Inappropriate experience for a job; and, • Changes in aircraft type with no experience compared to past routines or expectations, etc. Familiarity/Routine job with: • The task; • Safety procedures; • Ground Support Equipment (GSE) and tools (availability, quality, location, delivery and/or collection, identification, handling heavy or awkward items, etc.); and, • Paperwork (unavailability of relevant manuals or procedures, failures to complete paperwork correctly, etc.). Morale: • Personality conflicts; • Being unhappy with the work situation; and, • Inadequate incentives/motivations . Support: • Difficulties with support from other areas; and, • People unavailable in other areas, insufficiency of manpower. Page 7 of 15
  8. 8. Human Performance Maintenance Briefing Notes Human Performance and Limitations Fatigue: • Problems with tiredness, unusually slow working; • Disturbed sleep patterns, particularly at the beginning of a shift; and, • The balance between work and rest. Pressure / Time constraints: • High workload; • The workforce being spread too thinly over the jobs; • Many interruptions; • Too little time to perform the job; and, • Pressure of flight schedule. Shifts working: • Difficulties with shift patterns, time of day or night; and, • Communication at shift handover. Environment: • Weather inconveniences; • High noise levels; • Inadequate lighting; and, • Insufficient environmental protection, etc. Page 8 of 15
  9. 9. Human Performance Maintenance Briefing Notes Human Performance and Limitations VI Prevention of Human Failures in Maintenance Activities A series of Human Factor problems form an error chain. If any one of the links in this chain had been broken the incident may have been prevented. It might be done by building in measures/defenses, which may not permit an error at one or more of the stages. A good example is J.Reason’s ‘Swiss Cheese’ Model, here below. Maintenance- related event Defenses Inadequate Productive Activities Unsafe Acts Preconditions Line Management Deficiencies Decision Makers Fallible decisions Figure 2 J.Reason’s ‘Swiss Cheese’ Model Page 9 of 15
  10. 10. Human Performance Maintenance Briefing Notes Human Performance and Limitations VI.1 Situational Awareness or “Knowing What Is Going Around You” Definition Situational awareness is a synthesis of an accurate up-to-date mental model of one’s environment and state. That means perceiving important elements (for example, feeling the cold as you walk outside on a winter morning), understanding their meaning (understanding there may be black ice on roads), and projecting this status into the future (appreciating that such conditions could cause the car to skid and consequently adapting your driving speed). The process of attention, perception and judgment should result in awareness of current situation. The aircraft maintenance engineer must be aware of: • Who is working around the aircraft to avoid injuries; • The status of the system he/she is working on; • The relationship between the reported effect and the intended rectification; • The possible effect of this work on other systems; and, • Consequence of his/her own actions for the others. In aircraft maintenance engineering, the entire team needs to have situational awareness, not just of what they are individually doing, but of their colleagues’ activities as well. VI.2 Use of maintenance check list: what is involved in maintenance environment In order to manage maintenance well, you should be able to match the issues below. The challenges for maintenance management: • Be fully aware of which maintenance work can lead to a major risk; • Put in place good defenses/protection to make sure these accidents are very unlikely, including: o Safety notices and devices; o Quality controls (permits, procedures, checklists); o Management controls (supervision and checking of tasks); o Highly competent maintenance teams; and, o Well-designed maintenance planning. Page 10 of 15
  11. 11. Human Performance Maintenance Briefing Notes Human Performance and Limitations • Base your maintenance program on major accident risk assessment; • Communicate well during shifts and between shifts; • Take special care of temporary or inexperienced maintenance technicians and contractors; • Do walk around inspections of maintenance tasks in progress; • Look for early signs of problems (e.g. a large backlog of jobs; excessive repair times; adverse feedback from staff); and, • Investigate near misses and accidents while learning from failure. VII Case study VII.1 Description of the event An operator performed a scheduled slide deployment test on doors 1L, 2L, 3L, and 4L. Two of the doors 1L and 4L didn’t automatically open and required manual opening with subsequent successful slide deployment. However, the operator’s engineering department noticed that pressure was still within the green band on both the emergency actuators and the diaphragms were not punctured meaning that the actuators did not operate. Upon further inspection it was found that the percussion mechanism on both of the actuators were not correctly positioned and locked. VII.2 Findings When the arming lever is placed in the ARMED position the activation lever moves under the release lever of the percussion mechanism on the actuator. If the door is then opened in ARMED mode the door lifts and the activation lever operates the release lever which in turn punctures the diaphragm in the reservoir to operate the actuator. Refer to Figure 2, on Page 12. Page 11 of 15
  12. 12. Human Performance Maintenance Briefing Notes Human Performance and Limitations Release Lever Activation Lever Figure 3 Door Emergency Actuation Mechanism Page 12 of 15
  13. 13. Human Performance Maintenance Briefing Notes Human Performance and Limitations Door 1L –Emergency Actuator Percussion Mechanism – Release Lever Position Release lever was not placed in the correct fully extended position. A gap can be seen under the knurled screw. Incorrect wire locking. Instead, should be locked to this point here. Door 4L –Emergency Actuator Percussion Mechanism – Release Lever Position Release lever was not placed in the correct fully extended position. A gap can be seen under the knurled screw. Incorrect wire locking. Instead, should be locked to this point here. Familiarity with Maintenance Manual procedures and illustrations Page 13 of 15
  14. 14. Human Performance Maintenance Briefing Notes Human Performance and Limitations VII.3 Recommendations • In order to reactivate the percussion mechanism, the following steps have to be accomplished: - Push release lever to the fully extended position against the spring and hold it; - Tighten the knurled screw, fully engaged in the bore of the release lever; and, - Safety the knurled screw by wire locking to the lug provided on the release lever. Release lever placed in the correct fully extended position with the knurled screw engaged and tightened • In order to avoid similar issues in the future, a caution has been included in the relevant AMM tasks to highlight that if the release lever is not placed in the correct position then the emergency actuator will not operate correctly when the door is operated in emergency mode. Familiarization with procedures and supervision/checking of performed tasks Page 14 of 15
  15. 15. Human Performance Maintenance Briefing Notes Human Performance and Limitations It is very important to read Warnings and Cautions. WARNING: calls to use of materials, processes, methods, procedures, or limits which must be followed precisely to avoid injury to persons. CAUTION: calls attention to methods and procedures which must be followed to avoid damage to equipment. VIII Summary of Key Points Since people design, build, operate, maintain, and manage potentially hazardous technologies, it is hardly surprising that their decisions and actions contribute, in one way or another, to unwanted events. However, mistakes made must be an occasion to learn from error in order to prevent these undesired events. Reminder of the main factors, leading to incite an error: • The nature of the workplace; • The quality of tools and equipment; • Whether or not supervisors or managers turn a ‘blind eye’ in order to get the job done; • The quality of the rules, regulations and procedures; and, • The organization’s overall safety culture, or indeed its absence. This Maintenance Briefing Note (MBN) is part of a set of Briefing Notes that provide an overview of the applicable standards, techniques, best practices, human factors, suggested company prevention strategies and personal lines-of-defense related to major threats and hazards that may affect maintenance. This MBN is intended to enhance the reader's safety awareness but it shall not supersede the applicable regulations and the Airbus or airline's maintenance documentation; should any deviation appear between this MBN and the Airbus or airline’s maintenance documentation, the latter shall prevail at all times. In the interest of aviation safety, this MBN may be reproduced in whole or in part - in all media - or translated; any use of this MBN shall not modify its contents or alter an excerpt from its original context. Any commercial use is strictly excluded. All uses shall credit Airbus. Airbus shall have no liability or responsibility for the use of this MBN, the correctness of the duplication, adaptation or translation and for the updating and revision of any duplicated version. Airbus Customer Services Maintenance Engineering Services 1 Rond Point Maurice Bellonte - 31707 BLAGNAC CEDEX FRANCE MBN Reference : MAINT – HUM_PER – SEQ 01 – REV 01 – NOV. 2006 Page 15 of 15