Human Factors On Aloha 243
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After studying the Aloha aircraft accident in 1933, our group is interested in the investigation in Human performances factors in maintenance and inspection. We have divided the investigation into 5 aspects:
Investigation:
The lack of inattention of the mechanics in practical procedures and policies planning.
Aloha Airline operated inter-island flight in Hawaii, therefore, Aloha 243 was operating in salt water environment. During each flight, there was a risk that the air saturated with salt and water vapour would enter the crevice when the aluminium sheets are failed to be bonded to the fuselage by epoxy adhesive, also corrosion of metal is stimulated.
After the accident, a full-scale investigation was launched by the United States National Transportation Safety Board (NTSB). It concluded that the accident was caused by metal fatigue exacerbated by crevice corrosion, the corrosion is exacerbated by the salt water and the age of the aircraft was already 19 years old as the plane operated in a salt water environment.
During the pre-flight inspection, there were no damages or abnormal conditions on Aloha 243 were found. Furthermore, In 1988, when the accident of Aloha 243 happened, Federal Aviation Administration did not have requirement that forced airline operators to carry out inspection between each flight. We can say that the crevice was exacerbated by the salty and moistly air, if inspection was carried out after each flight, this problem must be able to be aware and prevented.
As all the operators and mechanics are trained properly and qualified through adequate testes and examinations, they would be capable to consider about the risk that corrosion will be caused by salt water. Besides, following the authority regulations, they should also carry out any extra inspections specifically required according to the status of aircraft (eg: age, structural and functional properties etc) ensure the aging aircraft was not in risk or damages were made to the aircraft during the flight. (In this case, if inspection is carried out after each flight, accident will be prevented.)
Inspection between each flight besides avoiding accidents, it also helps engineers to understand what problems that would be aroused by operation environment. Pre-flight inspection of Aloha 243 was only carried out before the first flight each day which is inadequate. Besides, all inspection records at each inspection should be kept; it records all the status of the parts and help engineers to understand how the aircraft structures would be affected after each operation. According to these past experiences, the mechanics can able to give any advanced advices to engineers on maintenance and improve the design of aircraft.
The external and internal factors affecting the performance of maintenance engineers/ workers.
2a) External Sources — Stress
– Stress caused by surrounding environment (eg: flashing or strobing lights)
A flashing light is designed to attract attention, not only to aircraft, but also to the machines while doing the maintained check in the dark night. However, seeing a flashing light will raise the maintenance worker level of ALERTNESS. It may be very distracting and even fatiguing.
For instance, a flashing amber light from a fuel truck parked right in front of the cockpit at night can be very distracting if the maintenance workers are trying to complete with the flight preparation tasks.
Stress caused by concentration and overload
High skill stress of the maintenance worker can as the result of a high level of performance requirement for an extended period: for instance there are heavy workload During each maintenance working hour cycle .Those maintenance workers are maintain a high concentration (cause at night ,need to spend more concentration) and high level of skill stress. Their performance will be affected under the high level of anxiety.
It could also be work related (a difficult maintenance work about to begin or a strained relationship with management etc), or it could have a domestic cause (marital or financial problems). The result of psychological stress is that an engineer or mechanic may be over aroused and move into the area of poor performance: *concentrating on a single problem and not maintaining a complete overview of the whole flight check; *exhibiting poor judgments; *becoming disoriented quite easily and *becoming fatigued (worn-out, burnt-out) at an early stage.
2b) Internal Sources — physical (Fatigue) and emotional factors
Fatigue caused by lack of rest/ sleep
“Overload” may bring a high pressure on the physical and emotional stress on the maintenance engineers. A lack of restful sleep due to the shift duty on maintenance engineers leaves them fatigue. The human body will automatically shift its internal clock by about one hour a night. If the late shift worker continues to maintain the irregular schedule over the weekend he will be completely in phase with the night shift by the second week. The result of this changing working pattern makes them hard to fall asleep easily. They need to struggle to stay awake to handle their technical duties. The rapid changes in shift duty make the workers need to adjust their own living style to fit with it. Although this can be compensated by adjusting of personal lifestyles, unfortunately, it is not so simple to make this “lifestyle change” for most workers – Coping with “Shift work”. “Shift work is a total lifestyle change that permeates all aspects of living like: sleep and mealtimes, exercise and sport activities, interaction with one’s partner, kids, friends, and the community”. It is unlikely that many mechanics would be willing to sacrifice so much of their personal life in the interest of increased safety throughout the week.
Emotional factors
Even if the pitfalls of the night shift are successfully averted, human factors related to the midnight shift must be dealt with. However, the midnight shifts are usually the most undesirable work hours; therefore the mechanics with the least amount of tenure in a company are assigned to that time slot. Due to the undesirable nature of this shift, the morale of the average midnight shift worker is low.