Management Matters: How to Prevent Avoidable Accidents

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.

Human error

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.

Time pressure

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. 

Such was the case of a jackscrew assembly failure caused by excessive wear resulting from insufficient lubrication. Contributing factors included extended lubrication and end-play check intervals, lack of available parts, organizational norms, and regulatory oversight issues. (NTSB ALASKA 261 FINAL REPORT, The Operator’s Manual for Human Factors in Aviation Maintenance 03, NTSB AAR-O2/01 Final Report, Event Investigation.) 

The jackscrew operates the stabilator on the DC-9. This was an example of organizational norms causing the maintenance to be rushed and the jackscrew assembly did not get the proper lubrication. Over a third of the passengers on this ill-fated flight were employees or family members of employees working for Alaska Airlines. This is only one example of a totally avoidable accident that all started with maintenance. Obviously this is an investigation that would be carried out by the NTSB.


On a smaller scale, let’s look within our own organizations. How many incidences and accidents occur within our own walls that have costly consequences to us or our company? And more importantly how many of them are avoidable by identifying the common denominators and human factors that cause them, and placing renewed focus and training in these areas. Event investigations help organizations identify and understand multiple contributing factors to errors and violations.

When events are investigated, we are able to understand the contributing factors, and corrective actions that must be developed to reduce the likelihood of future occurrences. Deviations from existing procedures are uncovered during the investigations, and they are corrected. Ultimately, the number of events caused by human performance decreases. The operator saves both time and money by decreasing interruptions to revenue flights, rework, personal injuries, and equipment damage.

Over time, cultural changes occur within the maintenance organization as personnel are discussing events, contributing factors, and corrective actions. Positive results from internal audits, employees acceptance of voluntary reporting systems, and adherence to regulatory guidelines evidences itself not just an important focus, but a recognizable one, as the organization morphs to an overall safety conscious community.


Numerous post-event investigations have clearly demonstrated that failure to use documentation appropriately was a major contributing factor. Keep in mind paperwork is to maintenance as location is to real estate! Location, location, location … document, document, and document! Have you ever had to sit on a witness stand and explain your paperwork?

Challenge yourself by going back to your log entries, whether it be for maintenance, fueling activities, or other tasks, and notice if they are clear, concise, and understandable as you once thought when you wrote them. Many times when we do this, we can find we are indeed confused by our own entries after some time has passed.

n  A 2001 FAA study found that documentation is the leading contributing factor to maintenance events. In most cases organizational issues resulted in failure to use documentation that was available.

n   In 2002 a study of procedural issues from a NASA Aviation Safety Reporting System incident report showed that the following factors contributed to documentation-related errors: procedural design flaws, user errors, currency, accessibility of documents, and organizational practices.

Safety conscious

None of us work in a vacuum or bubble and we will never be able to totally eliminate human error. However, we can employ processes in combination with training and maintaining a safety conscious culture to eliminate avoidable errors that lead to avoidable accidents. And we can live by the Mechanic’s Creed, in the words of Author - Jerome F. "Jerry" Lederer:

“Upon my honor I swear that I shall hold in sacred trust the rights and privileges conferred upon me as a certified aircraft mechanic. Knowing full well that the safety and lives of others are dependent upon my skill and judgment. I shall never knowingly subject others to risks which I would not be willing to assume for myself, or those dear to me."