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The FTA is a tool that allows, through a structured approach, to identify the root cause of a problem.


Introduced by Kazuo Kawashima in 2002, then Vice-President quality of the Valeo group, it is a logical approach to solve complex problems. Using the classic tools of the search for causes (5 Why, PDCA, 5M…), it is rooted in the culture of the 3 real : Genchi – Go see, Genbutsu – The real thing, Gemjitsu – the Reality.

Step 1: Identify potential causes based on 4m

The FTA uses the Ishikawa methodology to identify the root cause in the 4M format and not 5M (the method assumes that the Management is rarely the cause of the problem). We find:

  • Material: Material or components necessary to produce.
  • Machine: equipment or tools necessary to produce.
  • methods: Environment and working conditions, standard, measuring system…
  • Man: Skill, training…

For each of these families, identify all potential factors that may have an adverse effect on the outcome. For this, we can call on experts, ask the study office, compare the good and the bad parts…

Step 2: Identify checkpoints

We need to define how, where and who controls each of the potential factors. The factors being the measurable elements in relation to the potential causes identified in the previous step.

Apply to ask everyone: because this checkpoint can be done at the supplier, at the carrier…

Step 3: Identify the standard ” level ” of the factor

For each of the factors, define the nominal value and its tolerance. This ” level ” must be clear and precise in the standard. If to find the values, you have to go to the customer contract or the supplier approvals, you have to answer “no“..

Step 4: Comparing good and bad parts

Comparing good and bad parts. Be careful to only use the parts of the same production. The challenge is to understand why the problem has arisen.

Step 5: Validate or invalidate the factor

Depending on the previous elements, the potential cause of the problem will be validated or invalidated. 3 cases are to be seen:

  • The set of steps 2 to 4 could be scrupulously verified with regard to the factor in question and everything is OK : the cause is rejected.
  • The set of steps 2 to 4 are not OK : no doubt that this factor is one of the causes of the problem.
  • 1 or more elements of steps 2 to 4 are not OK : doubt is allowed, additional investigations must be planned to lift it.
The team must confirm this judgement by trying to reproduce the defect.

Step 6: Find root cause for potential factors

For all factors that have been considered to have influence, it is necessary to look for the cause using a 5 why.

Step 7: Set up the action plan

For each root cause, set up a plan of action PDCA To remove the problem.


D. Lighter (2011) – Advanced performance in Health Care: Principles and methods

H. Aoudia, Q. Testa (2012) – Perfect QRQC

A.V. Rohel (2006) – PDCA/QRQC, Problem Solving method

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