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The hazards of risk stacking

Recognize potential threats and mitigate them

The first time you climbed into the left seat, you couldn’t help but feel a rush of adrenaline and excitement.

Photography by Chris Rose
Zoomed image
Photography by Chris Rose

You’re finally doing it—you’re becoming a pilot! But even as you pushed the throttle forward and the airplane’s tires broke from the surly bonds of Earth, you understood that flying is not a hazard-free activity.

There are risks involved, from adverse weather conditions to equipment malfunctions. Given this reality, it is likely unsurprising to learn there are critical concepts to help a student pilot recognize potential threats and time-tested steps to mitigate them. Risk stacking is one concept you must integrate into your preflight preparations.

Risk stacking describes the compounding of multiple risks, which can ultimately end in an accident. In other words, a catastrophic event could result from a confluence of issues or missteps that were each minor in scope.

The Swiss Cheese Model, developed by British psychologist James Reason, is a valuable tool for understanding risk stacking. The model imagines layers of barriers, like slices of Swiss cheese. Each slice represents a different defense to an accident, such as good weather, a well-maintained aircraft, and a proficient pilot. However, like Swiss cheese, each slice has holes in it. These holes represent potential risks, such as deteriorating conditions, poor decision making, or pilot fatigue.

When all the slices are stacked together, the holes don’t usually line up, meaning that the barriers are effective in preventing accidents. However, if the holes in two or more slices line up, it creates a “pathway to failure,” when an accident is most likely to happen.

You can do several things to avoid risk stacking and reduce your chances of having an accident. First, being aware of the risks involved in flying is essential. Being aware includes the obvious dangers, such as bad weather and mechanical failures, and the less obvious, such as fatigue and complacency.

Second, you should take steps to mitigate the risks, including getting enough sleep, staying current on your training, and following proper procedures.

Third, prepare to deal with unexpected events, meaning having a plan for what you will do if something goes wrong.

Risk stacking is a critical concept for student pilots to understand. Ultimately, the key to managing risks is maintaining a proactive and vigilant approach to safety. You must be able to identify potential hazards, assess the likelihood and severity of those hazards, and take appropriate action to mitigate the risk. Doing so can help ensure that you and your future passengers remain safe, and that accidents and incidents are minimized.

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Terrie Mead
Terrie Mead
Aviation Technical Writer
Terrie Mead is an aviation technical writer for the Air Safety Institute. She currently holds a commercial pilot certificate, a CFI with a sport pilot endorsement, a CFII, and she is multiengine rated.

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