Can cause a gradual deterioration of standards and lead to complacency

As a former air safety investigator, I was often presented with an accident or incident where one of the key elements of the event was the presence of a workaround or deviation to published procedures established by the organization or mandated by the manufacturer.

It’s a common problem in all organizations and is rooted in our innate ability to problem solve coupled with resource driven pressures to get the job done better, cheaper, faster. By resource I mean time, money, and labor.

Learn from experience

It is said that our experience is the sum of our mistakes. However, we are fortunate that by reading about other mechanics’ experiences — some of them bad — we have the opportunity to learn and improve our own performance daily.

Here is a famous accident that hit the news many years ago: This was an accepted workaround supported by internal work instructions. The process failed to anticipate the failure of ground support equipment as a DC-10 engine was hung with the pylon attached to the engine rather than separately as called out by the manufacturer. The engine is left over night with the forklift supporting the forward portion of the engine. The forklift loses pressure and the forks settle creating a twist in the rear engine mount which then cracks. The next day the engine change is completed, but the crack goes unnoticed. As the aircraft departs the airport the left engine departs the airplane along with most of the left wing lift devices. The aircraft goes down.

Here’s another (It didn’t make the news): An aircraft elevator jack screw was removed and sent for overhaul. Upon completion of the overhaul, it was received and sent back to the aircraft for re-installation. After some time, it was installed and when the required inspection was accomplished it was found to have broken limit switch seals and a damaged switch housing. The unit was sent back to the overhaul agency who estimated the damage at $15,000. Further investigation revealed that the unit was the wrong part number for that aircraft. The project manager objected because the unit was originally removed from the aircraft; however, it was found that the unit had been modified by the previous owner, and installed years before. The assumption and accepted practice was that, since it was the unit removed previously, it was acceptable for re-installation.

Standard operating procedures

The air carrier SOP (standard operating procedure) was written requiring the mechanic to verify a part’s acceptability for installation; which includes assuring the part was the right one for the aircraft. But their logic and the “rule of thumb” said that it was acceptable to install because of previously assumed installation history.

The root or contributing cause for many incidents or accidents lies in the failure of maintenance personnel to follow standard operating procedures. Often these systems contain some kind of double check system such as inspection buy back, ops check read backs, lock out and tag out, etc.

Key departures from maintenance SOP include:

  • Failure to perform an adequate turn over during a work stoppage or shift change resulting in missing key information;
  • Failure to follow a check list as directed by the aircraft maintenance manual;
  • Use of improper tooling, improper tool substitutions — or misuse of tooling;
  • Improper management of processes and their controls.

The point of maintenance processes and controls are to assure that high levels of safety and workmanship are maintained for the airplane to which they apply. Following them provides the means to avoid hazards as well as reduce the creation of hazards that are latent. It does something else that most people fail to realize, but on reflection becomes obvious — it promotes repeatability. If standards are high and followed, the quality will consistently reflect the standards. If a workaround is in place then repeatability of a lesser standard may become the norm.

Tolerance creep

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