Fault Tree Analysis (FTA): Know where the loophole is

With any system or line of work, errors are always going to be a part of the same. But, the one striking thing about the same is the more the errors; the more are the risks of failure. Finding the loopholes early on in the process does help in improving the success rate and even brings better precision to the project you are on. Fault Tree Analysis is a diagrammatic representation pointing out the faults through a system and the possible bifurcated causes behind the same.

If you have been inquisitive about the same, don’t worry, we have sorted you out with everything that you possibly need to know about Fault Tree Analysis.

What is a Fault Tree Analysis?

Majority of the developers suggest that the Fault Tree Analysis (FTA) is a deductive process. It is a process which finds the mistakes in a process and spreads them out in a flowchart to further understand the underlying causes behind the condition.

what is fault tree analysis

The developers who make use of this have explained saying that the primary objective behind this is to help understand the causes of the human errors in a system and the further underlying causes that could be hindering the faults along in the process.

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The visual representation of the analysis predominantly starts out with a single point which then bifurcates down based on the further possible causes, in the form of a tree and hence the name.

In expert terms, the “fault” in the system is considered as any of the undesired outcome from the process that the developers want to get rid of for good by finding what could be causing it in the first place.

In addition to that, the fault can further be classified into three categories – the primary, secondary and command fault.

Where did it stem from – the history?

When it comes down to the history of the Fault Tree Analysis, the same dates back to the early 1960s. For the most part, even then it can be further subdivided and categorized into several stages, namely the early, middle and the later years. These years have experience the growth and the evolution of the process and has since then refined more and more to become a better version.

Back in 1961, it was Bells Lab that used the fault tree analysis to further assess the design as well as the evaluation of both the civil as well as the commercial aircraft. Later, in the 1970s, the fault tree analysis became a common groundwork used in the aerospace industry.

Majority of the countries that heavily indulged in the process of algorithms and coding further made use of the fault theory to further propagate their possible outcomes. It was later in the 1990s that the fault tree analysis became a popular inclusion in the software and the chemical industry.

In the recent times, the use of fault tree analysis has been in use worldwide and is used by professional coders and a lot of other people around. It is considered as one of the best when it comes round to the safety and the reliability tools.

What are the Fault Tree Diagram Symbols?

If you wish to have a successful row with the fault tree diagrams, it is important that you know of the basics surrounding, knowing about the symbols being one of the most important parts.

As per the standard knowledge, there are predominantly two different types of fault tree notations, the events and the logic gates.

fault tree analysis symbols
Image Source: Cacoo

When it comes round to the external events, the same is denoted on the fault tree diagram with a home symbol. These kinds of events are the normal ones, that are expected to happen henceforth.

In case of an underdeveloped event, the same is expressed in the form of something that doesn’t need further breakdown or investigation for further analysis.

Lastly, a conditioning event is the one that further denotes some form of restriction to the logic gates in the overall diagram.

Knowing of the Gate symbols is important because that is what depicts the major part of the diagram. Before moving forth with it, it is necessary that you know about the different types of gates involved.

  • OR gate: This is the one wherein the event occurs when at least one of the input in the process takes place
  • AND gate: This is the one wherein an event occurs only when all the events have taken place
  • Exclusive OR gate: This is the one wherein an event occurs when one of the input conditions are met and not all of them
  • Priority AND gate: This is the one wherein an event only occurs once there has be a completion of a certain turn of events
  • Inhibit gate: This is the ones wherein an event occurs when all of the inputs have taken place as stated in a conditional event

What things do you need to consider?

Before you finally end up drawing out the fault tree analysis, it is important that you keep certain factors in mind that can further help improve the accuracy of the final results.

There are five different and important factors involved that we think is worth noting. To help you further, we are going to make a quick rundown of the same.

Start by identifying the issue

When it comes to drawing out a successful fault tree analysis, the very first in this is to start by identifying the issue involved in this. If you know what kind of consequence the failure is bringing around, it does make the process of understanding the issue a lot better.

Identifying this flaw first is a necessity you can’t avoid. Not just the fault, knowing the duration of the consequence and even why it’s happening can create a better and much clearer picture for this.

Obtain better understanding of the system

When you are analyzing the situation, it is quite important that you do obtain a better understanding of the overall system that is under scrutiny. Noting down all the possible causes, the possible requirements and the probability of the cause at the base level can further help in improving the accuracy in the diagram and in turn, for the overall process as well. If possible, you can also list out all the causes with codes, as per your convenience.

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Focus on the process

Once these above two steps have been sorted out, the next thing that needs attention is the actual fault tree diagram. Once you have sorted out the cause and found further loopholes into what is causing the discrepancies in the system, the next step to follow through is to sit down and finally make the fault tree diagram.

This is what makes all the difference. You can use standard templates or even come up with your own representations and then draw it out as per the needs.

Identify the risks

With the fault tree diagram done, the next step is to identify the risks involved. This isn’t that tough of a job because you already know the loopholes and the breaks in the process. This does help solve out more than half of the problems.

Once the risks are identified, it is easier for you to find ways to mitigate the condition to ensure smooth sailing of the system without any form of hindrances along the way.


Last but not the least is to mitigate the possible risk that you are expecting and witnessing around in the overall system. The criticality method is considered one of the best ways to mitigate the risks, but it depends on the level and the intensity of the risk that you are dealing with. You can easily follow through as per your needs.

How to create a Fault Tree Analysis?

With the basic factors out of the way, the next thing to focus on is the steps involved to make the fault tree diagram.

It is not that complex as many make it out to be, it is quite the opposite, actually.

  • In order to create a fault tree diagram, you need to first accumulate the factors as we mentioned around in the above subheading.
  • Keep in mind that a fault tree always starts off with a primary event or the undesired factor that is causing the system to be unresponsive.
  • Start the tree off mentioning the same at the top and branch out the further steps under that. Before you start creating a fault tree diagram, it is important that you also a have list of all the possible immediate causes that could further be affecting the efficiency of the system.
  • With these in place, you can layer and branch the faults and causes out to find a possible risk mitigation strategy that can help eradicate the fault for good to ensure the best success rate.

Benefits of using Fault Tree Analysis

When it comes down to the use of fault tree analysis, it is common for people to want to know why it is raved about so much.

Let us take a look at some of the benefits, shall we?

Easy adoption

The very first benefit that comes along with this diagram is the fact that it has a very easy to understand layout and is easy to adopt as well. It provides with a complete free will to the developers and administrators to edit and make changes according to their needs. It allows them to gauge the possible effects and even design a quality test based around that.

Better application

With fault tree analysis, the one thing that you wouldn’t regret is the fact that it comes with a wide applicability. What this means is the fact that it can be implemented around in various sectors and industries, as per the requirements around.

Better risk estimation

One of the primary benefits of the fault tree analysis is the fact that it provides with a better and wider picture of the possible risks involved in a system. The developers have the capability of identifying the shortcomings and the risks prior to the launch of the program which is quite amazing.

Suitable for complex systems

Lastly, the most important factor about the process is the fact that it comes in handy for the complex systems as well. It doesn’t have such limitations, which again, is pretty amazing. It helps with the safety management of the large scale complex systems.

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The End Note

Fault tree analysis is gaining traction and popularity over the course of time. If you have been facing issues with a system and need better clarifications for the shortcomings, laying it out on a fault tree diagram can help you see the risks and plan your mitigation accordingly.

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