The engineers and designers concerned with the human-factors should completely understand the particular system themselves prior to applying the human factor techniques to that system. The structure of an aircraft is created to work for an infinite period of time provided that the aircraft is inspected for errors as per the manufacturer’s instructions and the faults encountered from these inspections be properly removed through appropriate maintenance regime according to the design of the aircraft. The structural components installed in the aircraft do not last for that long that is why the credibility of these components is ensured through routine inspections and thus, they are either repaired or replaced accordingly. Standard Systems have been designed and implemented which promise to provide structural safety. The issue to be concerned about is the engineering study of the types of faults that might happen to take place and their expected time frame of occurrence based on which the schedule for inspections is designed. The basic types of faults are the cracks and the corrosions that are most likely to occur over a period time. The hazard can get worse if these cracks and corrosions take place simultaneously due to the reciprocating stretching effect of the structure caused by the extreme air pressure, load pressure and harmful chemicals.
The analysts recommend the time frame for the inspections to take place based upon the known growth rates of these types of faults. Since the formulated inspection system is a human-machine system, the human factors are also involved in its design process in addition to the mechanical-engineering factors. Both the inspections and the maintenance of the commercial aircrafts especially are regulated by the Federal Aviation Authority (FAA) in United States of America, Civil Aviation Authority (CAA) in United Kingdom and the other equivalent regulatory authorities in their respective countries. When the aircraft reaches the maintenance site then the work cards are produced to record the schedule and the inspection/maintenance work on it. Equipments responsible for obstructing the path of access are removed after which the aircraft is cleaned and then the access hatches are opened. Later on the comparatively detailed inspection is executed to figure out any faults that may require repair or maintenance such as cracks, corrosions, loose parts, etc. Every outcome from the inspection process is noted down as a non repair routine (NRR) item. When the repairs to the defected NRR item are made then the inspector approves these repairs. Thus, the inspector at the maintenance station is very busy while the aircraft is being inspected due to the heavy workload. Often, the inspector has to work over time. The work load decreases a bit when the preliminary inspection is performed and then it rises again toward the end of the inspection process when the repairs are waiting for approval. Most of the times, the inspection routine is performed at the night shift. Maintenance can either be done simultaneously with the inspection process or it can be executed after writing the non-repair routine items’ list. Many maintenance issues are known prior to the inspection process so they can be scheduled before the aircraft reaches the maintenance station. This maintenance is categorized as scheduled maintenance whereas the maintenance performed on the basis of the repairs required in the NRR list is commonly referred as unscheduled maintenance.
Every function involved in the process of inspection and maintenance has a different human factor that may affect the outcome of the process. For instance, the search process included in the inspection procedure rely critically on the vision and visual perceptions of the person carrying out this task that is the Aviation Maintenance Technician (AMT), who is also commonly known as the mechanic. Also, in the process of site access that is performed in the repair procedures, the human motor and motor output are very crucial. Similarly, there are several other processes in various departments of the aviation industry which are dependent on the human factors and thus, these processes are prone to human error.