![]() Make FTA Part of Your ToolkitĪn FTA works best in the design phase. And with a judicious use of Fault Tree Analyses, future disasters just might be (learn Lessons from 3 of the Worst Workplace Disasters). This horrible disaster could have been avoided. NASA management decided the risk was acceptable and gave the go-ahead for the launch. Ice had formed on the shuttle and it wasn't clear whether the O-rings would perform well in the cold weather. Organizational – Cold temperature the morning of the launch had engineers concerned.Previous flights had shown O-ring erosion had taken place, making the secondary O-ring useless. Technical – The O-ring joint had already been identified as being inadequate and a new design was underway.Both the primary and secondary O-rings failed, allowing heated gasses and flames to escape and make contact with the external tank, resulting in a structural failure. The O-ring sealed a joint connecting the solid rocket booster to the main part of the shuttle. Working down the tree, the cause of the separation was an O-ring joint failure. The top item on the fault tree is the solid rocket booster separation. This led to the destruction of the shuttle by aerodynamic forces.įrom there, they needed a Fault Tree Analysis. The investigation found that the right solid rocket booster separated, causing damage to the external tank. ![]() The space shuttle Challenger exploded 73 seconds after launch. By going through the diagram, you'll be able to find potential problems before they occur and put control measures in place to prevent them from happening. ![]() With enough data from past failures, you can predict the probability of a failure based on time and conditions. Of course, you won't be using it as a how-to guide to create hazards, but as a diagram to help you understand how these hazards come about. It can essentially function as a how-to guide for particular hazards and safety failures. As you work your way down the fault tree, continually ask yourself "How can this fail?" Once you've answered this question enough times, you'll have a tree that can be read from bottom to top to provide a step-by-step guide to those hazards. As more data is gained from testing or product history, you can add a statistical value to the events and predict failure and how reliable particular designs will be.Ī Fault Tree Analysis can be used effectively for many different potential hazards, from missile guidance system failures to cyber hacking. It enables a proactive approach in safety, right from the design phase. The next time you’re flying in a commercial jet, take a moment to be grateful this process was used to ensure the safety of the jet design and to identify potential problems before they could occur in real life.įault Tree Analysis is used to flush out potential system failures in advance, with the goal of eliminating potential failures altogether. This provides a structured approach to analyzing every component and system that could lead to a failure. For each component and all systems involved, risk assessments are performed with the aid of a Failure Mode and Effects Analysis (FMEA) and an FTA. From creating manufacturing equipment to assembling something as complex as a space shuttle, safety has to be factored into every single step of the design. Most do not realize the lengths engineers go to trying to ensure a safe design. Using Fault Tree Analysis to Improve Safety In the case of our braking failure, low brake fluid, a faulty master cylinder, and worn brake pads would all be drawn with the "or" icon because any of them on their own could cause the brakes to fail. The "or" gate is used to represent factors that could cause the failure by themselves, while the "and" gate is used to represent factors that could jointly contribute to the failure. The two most commonly used gates are "or" and "and". To simplify things and make the diagrams easier to read, FTAs use a standard set of icons to represent various gates and events. Once you draw all of these out, you'll have a representation of the event and its contributing factors. For example, low brake fluid might be caused by: For each of the of those potential factors, you would then list any activities that could lead to them.
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