February 6, 2012 | Mark Paradies

Monday Accident & Lesson NOT Learned: Why Do We Use the Weakest Corrective Actions From the Hierarchy of Safeguards?


Screen Shot 2014-07-21 at 11.37.45 AM

Last year, an employee of a major airline lost his leg when it was crushed by the wheel on a jetway in Knoxville, Tennessee.

I had a little extra time waiting for my flight to Atlanta from Knoxville last Friday so I asked the gate agent about the accident and what had been done to prevent a repeat. She said they were now required to have a spotter to make sure that no one got near the wheels while the jetway was moving (the wheels aren’t visible from the jetway controls).

That’s a Human Action Safeguard.

She also said that no one is allowed to use the stairs or get near the wheels while the jetway is in motion. That was already true when the accident happened but it was re-emphasized to everyone after the accident.

That’s a rule “quasi-Safeguard” that requires human action (compliance) to work.

Thus, a near-fatal accident had two human action related Safeguards that are meant to prevent recurrence of the accident.

Here is a graphic from our root cause analysis training…

Screen Shot 2014-07-21 at 11.43.07 AM


Now let’s evaluate the corrective actions used to prevent a possible future fatality using the graphic above…

First, we made a rule that required a spotter during moving of the jetway. This is a human action related Safeguard implemented through a rule. That is the second weakest type of corrective action (#5).

Reemphasizing a rule that previously failed (the second corrective action used) is a training related human performance Safeguard and is the weakest corrective action to prevent recurrence of the accident (#6).

What do you think? If you had a serious accident (lost leg due to crushing) and it had the potential to be fatal, would two weak corrective actions be enough?

Maybe we should start at the top of the hierarchy in the figure above and see what is the strongest reasonable Safeguard that we can employ is…


The Hazard in this case is the jetway weight and moving pinch point when the jetway is in motion. This is difficult to remove. (At least I can’t think of a way to do it.)


With current aviation operations, people are required to direct the plane while parking, unload baggage, refuel the plane, etc. Perhaps someday this will be done robotically, but for now, removing people from the jetway environment seems unlikely.


This one is possible. See this photo below from Frankfurt …


Screen Shot 2014-07-21 at 11.36.28 AM

They have implemented a guard to keep people away from the wheels.

Is it 100% perfect? No. People can go around the guard (jump over it?).

Is it better than warning people to be careful?


So I sent the photo above to the Knoxville airport management. We’ll see if there are changes in the future to implement a stronger Safeguard to the potentially fatal Hazard.



This corrective action (if implemented in Knoxville) only fixes one small set of Hazards – jetway pinch-points in Knoxville. This Hazard exists at airports around the world.

For corrective actions to the Generic Root Cause, the company would need to get airports around the world to guard the Hazard.

Next time you board a plane at your local airport, see what kind of Safeguard is in place. If you don’t see any, send the airport management (you can usually find a “contact us” link at the airport’s web site) a link to this posting.


How do you develop corrective actions? Do you start at the top of the Safeguard hierarchy and work your way down or do you start at the bottom and work your way up?

Your investigators should have their corrective actions evaluated to see how effective they will be. For potentially fatal accidents, I would recommend using the top three strongest on the list and sometimes allow the fourth if somehow the top three aren’t possible.

The bottom two can be allowed in combination with the top 4, but I would never allow them to be the only corrective action if a fatality was possible.

Stop taking the easy way out. Learn a lesson from this accident (and the corrective actions). Improve your corrective action process by using the strongest possible corrective actions.

Root Cause Analysis
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2 Replies to “Monday Accident & Lesson NOT Learned: Why Do We Use the Weakest Corrective Actions From the Hierarchy of Safeguards?”

  • Steven says:

    Is the punishment or disciplinary action to the incident involved person can be recommended in a taproot investigation report?

    • Mark Paradies says:

      First, the investigation should prove that the individual violated a well understood, positively enforced, rule that was consistently followed by others. That would be a SPAC Not Followed with no further root causes. Then, see the Corrective Action Helper® Guide for further recommendations. Thanks Mark

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