Human Factor

S kill, rule, knowledge-based errors; Skill-based behaviours  are those that rely on stored routines or motor programmes that have been learned with practice and may be executed without conscious thought. Rule-based behaviours  are those for which a routine or procedure has been learned. The components of a rule-based behaviour may comprise a set of discrete skills. Knowledge-based behaviours  are those for which no procedure has been established. These require to evaluate information, and then use  knowledge and experience to formulate a plan for dealing with the situation.”

Eye is very sensitive in the right conditions (e.g. clear air, good light, etc.),  has approx 1.2 million nerve cells leading from the retinas to the area  of the brain responsible for vision, while there are only about 50,000 from the inner  ears - making the eye about 24 times more sensitive than the ear. Visual acuity  is the ability of the eye to discriminate sharp detail at varying distances. Visual acuity is affected by: (a)  Physical factors such as: •      physical imperfections in one or both eyes (short sightedness, longsightedness), •      age. •      The influence of ingested foreign substances such as: •      drugs,  medication,  alcohol,  cigarettes (b)  Environmental factors such as: •      amount of light available  clarity of the air (e.g. dust, mist, rain, etc.). •      Factors asso...

Noise levels can be reduced (attenuated) by up to 20 decibels using ear plugs and 40 decibels using ear muffs . However, using ear protection will tend to adversely interfere with verbal communication.  It is good practice to reduce noise levels at source, or move noise away from workers. Hearing  protection should always be used for noise, of any duration, above 115 dB.   AME will almost  always need to use some form of hearing protection when in reasonably close  proximity (about 200 - 300m) to aircraft whose engines are running. Presbycusis - Hearing deteriorates naturally as one grows older. This is known as presbycusis.  Presbycusis affects ability to hear high pitch sounds first, and may occur gradually from the 30’s  onwards. When this natural decline is exacerbated by Noise Induced Hearing Loss, it  can obviously occur rather sooner.

          Perception  involves the organisation and interpretation of sensory data in order to make it meaningful, discarding non-relevant data, i.e. transforming data into information. Perception is a highly sophisticated mechanism and requires existing knowledge and experience to know what data to keep and what to discard, and how to associate the data in a meaningful manner.        Perception can be defined as the process of assembling sensations into a useable mental  representation of the world. Perception creates faces, melodies, works of art, illusions,  etc. out of the raw material of sensation.        Decision making  is the generation of alternative courses of action based on available information, knowledge, prior experience, expectation, context, goals, etc. and selecting one preferred option.         Decision making is also described as thinking, problem...

Safety In the Working Environment   Engineers should ensure that they keep the working environment safe.  Clutter,  rubbish, etc. is not only a nuisance to others, but can constitute a danger (e.g. a trip  hazard, fire hazard, etc.).  AMT should be careful when working on the  line not to leave objects when a job has been completed.  Foreign Object Damage  (FOD) is a risk to aircraft operating at an airfield. Types of  workplace hazards  include chemical, ergonomic, physical, psychosocial and general  workplace . ASC 2 of 2015 VRS   Work environment  is used to describe the surrounding conditions in which an employee operates.  W ork environment  can be composed of physical conditions, such as office temp., or equipment, such as personal computers. It can also be related to factors such as   work  processes or procedures. Safety When Working On Aircraft   Before operating or working on...

In the worst cases, human errors in aviation maintenance can and do cause aircraft accidents.  accidents are the observable  manifestations of error. Like an iceberg which has most of its mass beneath the water  line, the majority of errors do not result in actual accidents. “Iceberg Model” of Accidents  Some incidents are more  high profile than others, such as errors causing significant in-flight events that,  fortuitously, or because of the skills of the pilot, did not become accidents. Other  incidents are more mundane and do not become serious because of defences built  into the maintenance system. However, all incidents are significant to the aircraft maintenance industry, as they may warn of a potential future accident should the error occur in different circumstances.  As a consequence, all maintenance incidents have to be reported to  Mandatory Occurrence  Reporting. These data are used to disclose trends and, whe...

Work logging and recording is possibly is the most critical communication area in aircraft maintenance and has been cause of quite a few incident.  Record should be updated as work progress.  ensure that an adequate record of the  work carried out is maintained.  This is particularly important where such  work carries on beyond a working period or shift, or is handed over from  one person to another.  The work accomplished, particularly if only  disassembly or disturbance of components or aircraft systems, should be  recorded as the work progresses or prior to undertaking  a  disassociated  task.  In any event, records should be completed no later than the end of the work period or shift of the individual undertaking the work.   Such  records should include ‘open’ entries to reflect the remaining actions  necessary to restore the aircraft to a serviceable condition prior to release. In the case o...

Repetitive tasks   - tasks that are   performed several times during a shift,  or a number of times during a short time period,  e.g. in the course of a week.  Repetitive tasks can be tedious and reduce arousal (i.e. be boring).  Most of the human  factors research associated with repetitive tasks has been carried out in  manufacturing environments where workers carry out the same action many times a  minute. This does not generally apply to maintenance engineering. Main danger with repetitive tasks is that engineers may become so practiced at  such tasks that they may cease to consult the maintenance manual, or to use job  cards. Thus, if something about a task is changed, the engineer may not be aware of  the change.  Complacency  - an engineer may skip steps or  fail to give due attention to steps in a procedure, especially if it is to check something  which is rarely found to be wrong, damag...

Illumination  -  lighting both within the general working environment and also in  the locality of the engineer and the task he is carrying out.  Amount  of light striking a surface.  To work safely and efficiently, proper lighting conditions is required.  Cones in the retina of the eye  require good light to resolve fine detail. Colour vision requires adequate  light to stimulate the cones.  Inappropriate or insufficient lighting can lead to mistakes  in work tasks or can increase the time required to do the work.    Illuminatio n  availableability is important where the engineer needs it (i.e. both  in the hangar and one the line). Supplemental task lighting must be adequate in  terms of its brightness for the task at hand , which is best judged by the engineer.  When using task lighting , it should be placed close to the work being done,  but should  not be in the engineer’s line of s...

Sleep is a natural state of reduced consciousness involving changes in body and brain  physiology which is necessary to man to restore and replenish the body and brain. Five stages of sleep: Stage 1 : Transitional phase between waking and sleeping. Heart rate slows and muscles relax. It is easy to wake someone up. Stage 2 :  deeper level of sleep, but it is still fairly easy to wake someone. Stage 3 : Sleep is even deeper and the sleeper is now quite unresponsive to external stimuli and so is difficult to wake. Heart rate, blood pressure and body temp continue to drop. Stage 4 :  deepest stage of sleep and it is very difficult to wake someone up. REM Sleep :  the person is even more difficult to awaken than stage 4. Brain is active. It is also known as paradoxical sleep. Muscles become totally relaxed and the eyes rapidly dart back and forth under the eyelids.  dreaming occurs during REM sleep. Stages 1 to 4 are  known as N on-REM Sleep . NREM...

Social Culture  - The influence of social culture (an individual’s background or heritage) can be  important in determining how an individual integrates into an organisational culture.  The way an individual behaves outside an organisation is likely to have a bearing on  how they behave within it. Internal pressures and conflicts within groups at work can be driven by underlying social cultural differences (e.g. different nationalities, different  political views, different religious beliefs, etc.). Safety cultur e  is the term that we apply to those aspects of the organization’s culture that relate to safety performance,  Safety Culture. Cultures are the product of the values and actions of the organization’s leadership as well as the results of organizational learning.  Ref. ICAO HF Digest 10 -  Safety culture  - “a set of beliefs, norms, attitudes, roles and social and technical practices  concerned with minimizing exposur...

Incidents and Accidents Attributable To Human Factors / Human Error In 1940, it was calculated that approximately 70% of all aircraft accidents were attributable to man’s performance, that is to say human error Causes/ major contributory factors                 % of accidents in  which  this  was a factor     Pilot deviated from procedures                                          33  Inadequate cross-check by                                               26 Design faults                                                              ...