Shift\Task Turnover: The Operator's Manual for Human Factors in Aviation Maintenance

How important is a shift/task turnover in aircraft maintenance? Let's take a look at an historical accident investigation that helped change the safety culture in aircraft maintenance. The accident aircraft was an Britt Airways Embraer 120RT, N33701, operating as Continental Express flight 2574 which crashed in Eagle Lake, Texas on September 11,1991 as a result of an in-flight structural breakup, killing all 14 people on board.

According the National Transportation Safety Board (NTSB) aircraft accident report:

The evidence is clear that the events during the maintenance and inspection of N33701 the night before the accident were directly causal to the accident. Several errors were made by the individuals responsible for the airworthiness of the airplane. The Safety Board believes that the reasons for the errors and the overall failure of the maintenance program are complex and are not simply related to a single failure by any single individual. Consequently, the Safety Board's analysis of the maintenance and inspection program concentrated on the systemic reasons for the accident, as well as the specific errors made by the individuals concerned.

The Safety Board concludes that the upper row of screws that had been removed from the leading edge of the left horizontal stabilizer was undetected because the approved procedures in the General Maintenance Manual were not followed by the maintenance, supervisory and quality control personnel directly charged with evaluating the airworthiness of N33701 before it was returned to service.

The following are examples of substandard practices and procedures and oversights by individuals, who had an opportunity to prevent the accident:

The second shift supervisor responsible for N33701 failed to solicit an end-of-shift verbal report (shift turnover) from the two mechanics he assigned to remove both horizontal stabilizer deice boots. Moreover, he failed to give a turnover to the oncoming third shift supervisor and to complete the
maintenance/inspection shift turnover form. He also failed to give the work cards to the mechanics so that they could record the work that had been started, but not completed, by the end of their shift.

The Safety Board believes that the accident would most likely not have occurred if this supervisor had solicited a verbal shift turnover from the two mechanics he had assigned to remove the deice boots, had passed that information to the third shift supervisor, had completed the maintenance shift turnover form, and had ensured that the mechanics who had worked on the deice boots had filled out the M-602 work cards so that the third shift supervisor could have reviewed them.

Chapter 4, Shift\Task Turnover, of The Operator’s Manual for Human Factors in Aviation Maintenance states:

Shift and task turnover are critical periods in aircraft maintenance activities because workers relay crucial information for ending a shift and starting another. This can also apply to an exchange of task information within a shift. Efficient and effective turnovers require adherence to policies, procedures, planning guidelines, teamwork, and effective communication practices. The classic challenges associated with fatigue, distraction, false assumptions, personnel conflicts, cultural prejudices, and failure to properly document can negatively affect the quality of shift turnover as well as task turnovers within shifts. Events have shown us that inadequate information exchange during shift and task turnovers can have serious consequences.

If you cannot complete a maintenance task before you leave work, it is your legal responsibility to document what has been accomplished and/or what has been left undone. This vital information should then be passed down to the next mechanic taking over the job or as a reminder to yourself if you will be the one resuming the task at a later time. This is also important to do prior to taking an extended period away from the job site such as a lunch break.

A shift/task turnover may be a mundane task, but this accident is a sobering reminder to take an extra few minutes before you walk away from a maintenance task to record this critical information. It could mean the difference between life and death.


It amazes me that a country as great as ours is so intelligent on one side yet ignorant (or conceited) on the other. Ask yourself why civilian aviation (GA, commercial, and corporate) suffers from these types of tragedies and the military doesn't? Could it be that the military has built a better mouse trap?

As an Air Force veteran I say, you're damned right they have! When was the last C5, C141, C17, or any other military aircraft type crash that "...the maintenance and inspection before the accident were directly causal to the accident."? You're gonna go back MANY , MANY years to find that answer!!!

And it's NOT rocket science, it's discipline! It's identifying, delagating and accepting responsibility, it's having chain of command and most importantly, it's having authority and using it.

Why can't the civilian side do as the military does? Because they CHOOSE not to...

Good point, procedures and processes make a big difference along with the skill level, training and even language of the technician.
Is the work safer from a 145 repair stations because of all the process, training requirements and QC loops when compared to a independent shop?
How about a 121 carrier with even more processes and procedures? Does the use of 'lowest bid" non certificated, ESL workers effect safety or doe their procedure and process manual mitigate this as a issue.
The military does have a great track record, no dispute. I was reading the June issue of Air & Space article on the F15 when the following caught my eye; "F-15Cs require 11 hours of maintenance for every hour of flight". Is this a factor? I don't think GA could afford a 10-1 maintenance to flight ratio if this is a true representation.

Bob, I don't believe military accident investigation has the same scrutiny that civilian does, and findings aren't always made public knowledge. In my 4 years in the USAF I saw far more shady maintenance than I ever have in nearly 30 years civilian.

With all due respect, my anonymous friend, I believe you're half right in that "I don't believe military accident investigation has the same scrutiny that civilian does". It has much, much more! Trust me, I've been involved in both. But where I have to adamantly disagree is with your "shady maintenance" comment. We seem to have close to the same amount of experience in both military and civilian aviation so allow me to tell you why your statement holds no water.

Every military technician receives much more initial and recurrent training and education than thru civilian routes. They're continually schooled in the latest and greatest methods and procedures, and have access to current service manuals and mfgr's information for all technologies they service, civilians aren't always that current.

Each tech is directly responsible for their work as do civilians. The difference being the military regularly charges, processes and disciplines technicians who violate rules and regulations regardless of degree of fault or failure. The FAA does NOT, for what ever reason - they do not!

Those military technicians suffer loss of pay, rank and sometime service as a result of violations. Civilians are not likely to be prosecuted much less be fined or even less likely lose ratings and even in extreme cases where lisences or CRSs are lost does it stop offenders from maintaining aircraft as the FAA watches almost helplessly.

Maintenance organizations that manage transportation assets face a triple challenge. They must keep mission critical assets available and on-schedule, do so with support people and parts spread out across a network, and respond to a wide spectrum of maintenance problems. The diversity of maintenance tasks is substantial. Maintenance can range from frequent, routine inspections to repairs completed on the flight line, and from complex troubleshooting involving the removal and replacement of components, to complete overhaul of components, engines, and even entire aircraft.

Both must ask themselves tough questions like: Are we keeping aircraft ready to fly efficiently? Is the inventory working optimally for our operation? Are we making the most effective use of overhaul? and Is the logistics chain compatible with the requirements of maintenance events? The civilian answer is soley predicated on money where as the military response is primarily based on proficiency.

The proof of that is in the pudding in that civilian aviation has arguably been degrading maintenance thru outsourcing to the detriment of U.S. businesses and technicians nation wide. Now that's not the only example but it's a glaring one.

Today, MRO providers struggle to balance competing business needs of high aircraft utilization, keeping down investment in parts inventories and supporting assets, and high productivity. The military still has that same get 'er done attitude I grew up with in the 60s and 70s. Never, I say again NEVER, in my almost 8 year military career was a decision on how to fix an aircraft based on cost! I dare you to say the same about civilian life...

USAF 1969-1977
A&P IA 1980-Present