Human errors account for an alarming rate of failures throughout a broad range of industries worldwide, aviation being no exception. Methodologies for analyzing human error have been developed and adopted in several industries including aviation with NASA being a leader in this effort.
With high failure rates and the fact that the results of human error can result in enormously costly failures, including the loss of life, the need for human error analysis and safety assessment is crucial.
The study of human factors originated during World War II when young farm boys were flying complex machines less than 40 years after the horse was replaced as the major means of transportation. Thanks to aviation, the science of human factors was developed and is now used extensively in the nuclear power industry, the trucking industry, and the medical field.
We in the maintenance arena are certainly more than technically proficient and qualified by our training and certification to carry out maintenance tasks. But this is not enough to prevent accidents from occurring. In fact, human error was a vital factor in 80 percent of all accidents, from the first powered flight in 1903 to the present — FAA data indicates that 12 percent or better were maintenance or inspection related!
Greek accident investigators have concluded that human error led to the depressurization and crash of the Helios Airways Boeing 737-300, killing 121 people. On Aug. 14, 2005, the aircraft left Larnaca, Cyprus, on the way to Athens with six crew and 115 passengers. The previous evening, the 737 underwent a maintenance check, during which the ground crew left a cabin pressurization setting on "manual" mode, according to the final accident report released by the Hellenic Air Accident Investigation and Aviation Safety Board.
Sadly so often the loss of life is avoidable. The direct causes cited for the crash included the crew's failure to recognize that the pressurization selector was in manual during preflight procedures and checklists as well as failure to identify warnings or reasons why they were set off. The crew suffered incapacitation due to hypoxia, leading the aircraft to be flown by the flight management computer and autopilot.
How often we hear the cliché “we are all human,” meaning we all make mistakes. In our business we don’t have that luxury, and often, we as maintenance technicians, (or the occupants of an aircraft) don’t have a second chance. Matter of fact, the occupants of the aircraft place their unquestionable trust in those that maintain aircraft, which translates to “it all starts with maintenance.”
When we unintentionally deviate from the required, intended, and expected action an error is the result. There are two types of human error, active and latent. Active errors have results that are almost immediately identifiable. Latent errors are errors that do not result in immediate consequences and often show themselves much later. Unfortunately for maintenance, latent errors are prevalent, and may often result in the loss of property or life.
The infamous “Dirty Dozen” human factors account for the majority of errors. It therefore becomes imperative to identify the types of errors in maintenance tasks that occur in our everyday work, and which human factors cause these errors, to determine what we can do best to prevent them.
One immediate human factor significantly impacting day-to-day operations in maintenance is time pressure. When an aircraft is “down for maintenance” it is subject to loss of use and loss of revenue. So before the aircraft even arrives at the maintenance facility there is already existing time pressure to get it airworthy again. With the clock already ticking when the airplane arrives at our shop, those of us who must make the repair find ourselves already behind the eight ball.
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