Root causes - operator's actions

Steve Prevette

Deming Disciple
Staff member
Super Moderator
I recommend you read the second story here ->

Quote: Later when Sante Fe achieved the highest reactor operations inspection result, the senior inspector said “Your guys made the same mistakes – no, your guys tried to make the same number of mistakes as everyone else. But the mistakes never happened because of deliberate action. Either they were corrected by the operator himself or by a teammate.”

Steve Prevette

Deming Disciple
Staff member
Super Moderator
How about "S*** happens"?

Read the linked in quote above about the Santa Fe.

And systems should be designed, people trained, managers lead such that the results are NOT affected by S***. When S*** happens, which it will, the overall system is resilient enough to withstand the challenge.


Quite Involved in Discussions
IIRC the red beads thing was related to humans seeing red beads as black out vice versa thus people carrying out the experiment are unable to get the same result each time it's repeated and the same result as other people carrying out the same test.

This complaint isn't about a human error resulting in defective parts getting to the costumer. This is about a final process with 100% inspection as part of the process. Basically it's a cleaning the part up type of process before placing in the final packaging. The defect is due to the operator not cleaning the part up before boxing up. It appears to involve a deliberate attempt to cover this up to supervisor's spot checks. Gross negligence is suspected.

In some ways you could argue that systems weren't in place in a robust way to catch this negligence before reaching the customer. I argue that. However you do have to rely on operators to some extent. Systems to check their work but you can't check everything they do, only spot check. Unless the risks need it and costs to carry out the additional checks that could prevent similar claims are not too great to warrant the work. If necessary systems to prevent such issues make the parts uneconomic then the work isn't worth doing or the systems aren't possible.

Sorry rambling again.


Operator deliberate negligence.
Poor supervision.
Defect is not just a judgement failure or inability to detect. You hold the part you see the defect then you remove the defect using a very simple action.
Boring work for sure but it's one where you can take the time you need to get it right so pressure isn't great.
Support was always available if the workload needed extra operators.
Boundary samples, working instructions, visual instructions of defects and what actions are needed to remove the defects, etc are in place.


Involved In Discussions
I know seeing it but I don't have access to my index for handy posts (of which I know this is on it).

However: aerospace also has a nice categorization:

1. Lack of communication​
2. Distraction​
3. Lack of resources​
4. Stress​
5. Complacency​
6. Lack of teamwork​
7. Pressure​
8. Lack of awareness​
9. Lack of knowledge​
10. Fatigue​
11. Lack of assertiveness​
12. Norms​
Interesting Read - Human Factors as Root Cause This one?

Mike S.

An Early 'Cover'
It is very difficult, sometimes perhaps impossible, to prevent failures when a person is deliberately not doing what they are supposed to do, or deliberately doing something they are not supposed to do. That's one of the few times "fired employee" might be a valid corrective action.


Quite Involved in Discussions
Moved employee to another role is the CA told to the customer and that's been accepted. But writing up the root cause for non-detection / occurrence of defect isn't as easy I think. Detection wasn't made because the operator wasn't checking parts. Well good parts on the top layer with rejects below so they detected the defect I guess to know it needs hiding so their serviceman or supervisor didn't spot them when taking them to warehouse.

A potential sacking situation? Well precedent was set when this happened once before and nobody got fired. That's another issue perhaps. There's more needing to be fixed here. Quality isn't at the heart of the business?

We're reacting at times when our proactive measures fail. We use typical automotive practises like PFMEA, control plans, etc. We have a history of lessons learned from previous CAs. There's all the working instructions, visual aids and master samples in place. Operators doing the work have been doing it for some time and are considered trained. Additional operators available if struggling so not much pressure. It's repetitive but it's easy work to get right.

So when the operator doesn't do what is needed of them and we get rejects then operator error or more likely operator deliberate action is the most probable cause.
A common problem rarely discussed is the organization hiding it's lack of process control behind the cloak of "operator error" - also known as " who's going to fall on the sword? ".

This is why I stress " effective root cause(s) determination ".

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