CFIT and Normalization of Deviation Bias

#FlySafe GA Safety Enhancement Topic

5 min readNov 17, 2023

Make no mistake, human beings are programmed to push their limits. In a society where records are made to be broken, training, coaching, and practice are designed to progress our performance over time. This yields continuous improvement of output and production efficiency. In order to keep up, many people are eager to take advantage of a shortcut, but pushing the limits has its limits.

FlySafe illustration. — As pilots gain more experience, they are also more at risk of pushing their limitations.

The General Aviation Joint Safety Committee (GAJSC) study of Controlled Flight Into Terrain (CFIT) Accidents suggests that human biases may compromise effective pilot decision-making and lead to CFIT accidents. To minimize the risk, it’s important to recognize these biases and learn how to effectively manage things within our control and plan for dealing with the unexpected.

We’re All a Little Biased

Human biases are patterns of reasoning that weigh the value of information according to pre-conceived beliefs. Biases present as a prejudice in favor for or against one thing, person, or group compared with another; often in a way considered to be unfair. Normalization of deviance describes the human tendency, often well intended, to deviate from established procedures and norms over time and to accept those deviations as new norms. These deviations are sometimes referred to as operational drift and can be influenced by the Dunning-Krueger Effect that has to do with self-assessment of one’s capabilities.

In any process, limits are established to define and ensure acceptable performance. Limits are often safety driven and, if they are well designed, there is a cushion of safety to compensate for human, machine, and operational environment variations. Thus, we are comfortable with the notion that exceeding a limitation, by just a bit or for a brief moment is not likely to result in catastrophe. But because we are human, this comfort with brief excursions from limits can cause big problems over time.

Because we want to conserve energy and operate efficiently, we tend to push performance limits. Exceeding aircraft speed or weight limitations by “just a bit” will allow us to be more efficient, and after all, we have a safety cushion to rely on. Over time we come to accept deviations and they become our new norms. But once we’re comfortable with the new norm we might be tempted to push that limit yet again. This tendency to progressively exceed limits is known as operational drift. Each deviation is so slight that it seems inconsequential until one day we have a failure.

The Dunning-Kruger effect has to do with the tendency of people who are relatively inexperienced in a task to overestimate their ability with respect to it.

This may explain some of the overly confident behavior of some low-time pilots. Conversely, more experienced practitioners tend to underestimate their abilities. They may well be taking their previous experience into account when making conservative estimates of future performance. Even so — pilots who are new to the game and old pros are equally susceptible to Normalization of Deviation Bias.

Operational Drift & CFIT

Being overly familiar with an environment can lead to operational drift. Pilots new to an area are likely to insist on excellent ceiling and visibility conditions before attempting flight. But as they become familiar with the environment, they may accept less-than-ideal weather conditions. This practice can reduce margins of safety to the point where VFR flight is no longer possible and controlled flight into terrain becomes more likely.

So, what can you do about it?

First of all — everyone is susceptible to human biases, so being aware of that fact is the most important step. Next, it’s impossible to know if we’re exceeding limitations if we don’t know what the limitations are, so it’s vital to document and reference them. Assess your pilot experience and comfort level with respect to various mission and environmental conditions and write down your personal minimums. Parameters to consider are associated with the acronym PAVE — Pilot, Aircraft, enVironment, and External Pressures, including:

Pilot — certification level, total experience, recent experience, health, fatigue, stress
Aircraft — performance, range, instrumentation, navigation equipment, weather avoidance equipment
enVironment — topography, runway and approach aids, wind and weather, lighting conditions
External Pressures — employers and passengers, schedules and deadlines, expenses

Once you have established your personal minimums you can adjust them for specific conditions.

A word of caution: if you’re going to adjust a previously determined minimum, always do so in a more conservative direction. In other words, if you want less conservative minimums, you must acquire pilot and aircraft capability to ensure safety. An example would be a flight operation that wants to operate to Category II approach minimums must have specially trained crew and navigation equipment, as well as recent experience to fly the Cat II approach.

Finally, refer to your personal minimums and only operate within those limitations. Periodically reassess your limitations with a flight instructor. They can provide perspective and consistency and can offer coaching for improvement, allowing you to push your limits safely.