The BIRTH of the WHY Tree

Where did the WHY Tree originate?

I become aware of Fault Trees in the 1970's. This was almost inevitable, given that I was a chemical plant reliability engineer at the time, and was charged with researching the "state of the art" respecting reliability principals.

I discovered that Fault Trees were initially developed in the mid-1960's by Bell Labs to help evaluate the reliability of the Minuteman Intercontinental Ballistic Missile (ICBM) Launch Control System.

It's important to note that Fault Tree Analysis was originally designed to help evaluate the theoretical reliability of a system in its design-state, so that overall reliability could be improved while the project was still "on paper" (as in the ICBM system).

As an engineer, with the typical engineering way of seeing and thinking, I quickly grasped the format, symbols, and even mathematical intent of Fault Trees. But as my chemical plant focus shifted from evaluating overall system reliability to improving component reliability, I began applying the structure of the Fault Tree to help explain the causes of actual component failures in our operating chemical plants.

I remember doing "failure analyses" in many different chemical plants, explaining my conclusions with "Fault Trees."

After going into business myself for myself in 1985, I began to teach other people what I had learned about doing "Root Cause Analysis." At the time, I taught people to use "Fault Trees" as the backbone and driving force of a Root Cause Analysis.

Then it happened.

In the late 1980's, while teaching a Root Cause Analysis class in Fort McMurry, Alberta, Canada (in the Interpretive Centre across from the Sawridge Hotel), a chain-reaction of students rose their hands while I was teaching people how to use Fault Trees, saying:

• Student #1: What you are teaching is not a Fault Tree. Fault Trees are specific devises used in the design phase of a project to determine overall system reliability. (Note: the student was right -- I was wrong.)
• Nelms: Well, the structure is the same, isn't it?
• Student #2: I don't even like the name! Why would you use the name "fault" in a "root cause analysis?" People will think you're trying to find FAULT!
• Nelms: Well, uh, ummmm, (backtrack, sweat beads, and then a flash of BRILLIANCE). I said "well, what do you think I should do?"
• Student #3: Keep the technique -- it's a great technique -- but don't call it a FAULT tree. First of all, it isn't, and secondly, it's terrible word.
• Nelms: What should I call it.
• Student #4: (a nameless woman): If I were you, I'd call it a WHY Tree.

The WHY Tree is a trademarked name for a specific way of both driving and/or mapping the course of a Root Cause (or Latent Cause) Analysis.

More about WHY Trees is coming!