Go or Stay? Getting Personal with Your Pilot Minimums

Maybe you are planning a flight to visit your grandkid on their first birthday, or perhaps you are flying to EAA AirVenture for the very first time. Even more excruciating is the decision to press on to your destination when the weather encountered in flight is far worse than what you originally anticipated or had hoped for. A flight with some initial acceptable risks and challenges now becomes one with discomfort, and perhaps disappointment for you and your passengers if you must turn around or land short of your final destination. If you have some self-awareness, that little voice in the back of your mind wonders what the National Transportation Safety Board (NTSB) final report might say about your poor decision to press on.

You often hear pilots blame this on “get-there-itis.” That is, the pilot departed and continued on into adverse weather because of outside pressures as well as the intense desire and alternations of confidence and misgiving to complete the mission. It’s the Little Engine That Could mentality, or “I think I can, I think I can” belief that may have been drilled into them over the years as a kid. I don’t pretend to be a trained psychologist, and it’s not to say that this “try-and-try-again” mentality isn’t useful for other aspirations in your life. In aviation, however, some pilots become caught up in this way of thinking too often, and it usually doesn’t end well.

The decision to press on, despite the conscious, elevated risk that has just entered into the picture, is a new branch growing on this budding accident tree. The discussion should not be wrapped up in why the pilot chose to continue on but instead focused on the underlying cause of why they made a decision to launch in the first place without an actionable, low-risk plan to turn around or terminate the flight early.

Other than how much reserve you have in your bank account, weather limits your flying activity more than any other physical factor. There’s no doubt that some flights are more challenging than others, especially as they relate to weather. Finding the best time to depart or finding the optimal route or altitude often comes with more questions than answers. From the perspective of risk, each pilot is inherently unique. What represents low risk to one may be high risk to another. Nevertheless, anything that adds these challenges to the flight needs to be controlled.

But how does a pilot objectively quantify risk from a weather perspective? The short answer is that there’s no easy approach to quantifying risk for any given route of flight, other than trusting your gut, which may not always be reliable given the circumstances surrounding the flight itself and previous experiences when confronted with specific weather challenges.

No matter where you get your weather guidance as required by FAR 91.103 (a), the data you will use to make critical decisions about time of departure, route of flight, and cruise altitude, as well as your final decision to go or stay, is often a free-for-all. That is, weather reports and forecasts, sometimes quite complex, are thrown at you to see what sticks. There’s no question that for some pilots, much of it does, in fact, stick. The bad news is that the popular heavyweight aviation apps and services such as Leidos (formally Lockheed Martin Flight Services) are all guilty of throwing a bunch of weather guidance at pilots to see what sticks, hence the reason we continue to see weather-related accidents that include some pressing on into adverse weather they had not anticipated.

The real dilemma is that there is no efficient (automated) way to objectively quantify the risk on any given flight. But what we do know is that risk is very personal, and that’s not something these services directly integrate into their application or discussion as a route-based approach. In the end, it’s left up to the pilot to take that next giant leap to quantify the risk.

A difficult question to fully address is to what extent does a pilot’s individual personal weather minimums weigh into their decision to fly, and how can they be integrated into their preflight planning? Personal minimums, in general, represent a set of criteria, rules, guidelines, and procedures to help a pilot decide on the conditions and circumstances under which they can begin or continue operating a flight. These should encompass all elements that may add risk to the flight. Certainly, weather is one that adds risk to every flight.

In this context, personal minimums allow you to further tailor, quantify, and acknowledge the risk you are willing to assume, thus adding a margin of safety based on a set of criteria coupled with your own self-analysis and level of flight experience. In this case, “minimums” reference the minimum acceptable weather conditions at an airport or along a route of flight. Personal weather minimums are thought to be more conservative than the minimums set by the FAA, but applying them is 100 percent optional. And therein lies the open manhole.

As a flight instructor who has been teaching pilots how to minimize their exposure to adverse weather for the past 25 years, I am intimately aware of how few pilots understand how to interpret many of those complex charts and diagrams the FAA touts as essential. Since I’m a meteorologist, pilots and other flight instructors come to me as online students to learn what all of those H’s and L’s they see on the prog chart really mean to them. On one flight, they may have experienced little or no weather issues, while a seemingly similar weather pattern on a subsequent flight was fraught with poor or challenging weather they did not anticipate.

I wish there was a simple answer. If there was, I would not be giving it away for free—it would be worth millions. A common contributor to many fatal accidents is the pilot’s inability to definitively assess the hazard prior to departure from the relevant weather guidance available prior to flight. Therefore, the lack of sufficient weather reports and forecasts and their accuracy are not the core concern, but instead the primary contributing factor is that general aviation pilots have a difficult time consuming the forecast guidance in order to develop a plan as a precursor to making a decision to fly or continuing a flight. This is further compounded by many pilots’ lack of aviation weather knowledge.

Even though high-resolution weather forecasts are now more robust and have become increasingly ubiquitous online, pilots are not utilizing all of this information to their advantage to assess the risk. A GA pilot is not a trained meteorologist and often has a difficult time distilling all of the available information to make good preflight and in-flight decisions, especially when challenging weather is more likely than not.

It’s a gross understatement, but the weather is quite complex and requires a challenging dialogue. Pilots tend to prefer an easy solution (e.g., a few taps on a smart device or making a quick phone call to a briefer) to get their weather information and let someone else interpret it for them. Much of the weather guidance used to make an informed decision to fly on any particular day and time is spread over many different and sometimes complex charts, diagrams, and textual reports they never were taught how to interpret. As such, they often do not have a comprehensive approach that seamlessly integrates all of the pertinent weather guidance to make it obvious if they will encounter adverse weather along a proposed route of flight.

As mentioned earlier, anything that adds risk to the flight needs to be controlled. Both fatal and nonfatal accidents take place in adverse weather elements, such as strong and gusty surface winds, airframe icing, turbulence, reduced visibility, low ceilings, high density altitude, and/or threats associated with deep, moist convection. All of these elements add risk to the flight and must be evaluated based on the departure, en route, and arrival phases of flight. They need to also take into consideration time of year, time of day, type of aircraft, and perhaps the terrain over which the flight takes place.

Pilots often are lured into thinking that personal minimums are always about a single threshold. That may work to some extent for some. However, with weather, one thing that helped me over the last two decades is to create three buckets of risk—low, moderate, and high. Think of this as a simple traffic light concept—green, yellow, and red—whereby each personal weather minimum category you define is evaluated at the departure and destination airports and along the route of flight based on the forecast weather available for a specific time.

Green is used to define a conservative threshold. When the forecast weather is equal to or better than this threshold, the flight risk from a weather perspective is deemed to be negligible or low risk. Red, on the other hand, is at the opposite extreme. Red defines the pilot’s actual personal weather minimums. That is, if the forecast weather is the same or worse than this threshold, the flight risk is deemed to have a high risk based on these minimums. Lastly, yellow advises caution. In this case, the forecast weather is better than the pilot’s personal weather minimums (i.e., red) but worse than the conservative threshold (i.e., green). Yellow is deemed to be of moderate risk as the weather is forecast to approach your personal weather minimums.

This three-bucket method tends to work a little better since it allows you to float the risk across a range of values and not just straddle a hard line in the sand that most pilots employ. Moreover, the goal is to lean toward the conservative minimums that create a margin of safety. There’s probably an underlying psychological element that may factor in as well. Green is more attractive than yellow or red. You are free to make that moderate (yellow) risk as wide or narrow as you see fit.

The challenging part of this exercise has less to do with setting or determining your own personal weather minimums. In a few minutes, most pilots can figure that part out. The challenge is how to evaluate the weather forecast at your departure and destination airport and along the route against these personal minimums for ceiling, visibility, wind, icing, turbulence, and thunderstorms. Unfortunately, as mentioned, there’s no easy (automated) way to do this without consuming a great deal of your time. That data for this exercise is indeed freely available. What’s missing is the automated application of those personal weather minimums against all of this useful guidance.

If you want to do this manually, you might consider using the graphical forecasts for aviation (GFA) found on the Aviation Weather Center website at aviationweather.gov/gfa. For example, let’s assume your ceiling height personal minimum at your destination airport is 700 feet. If you are landing at 0300Z at Maryland’s Carroll County Regional Airport (KDMW), which is not served by a TAF, you should expect the ceiling will be at or below your personal weather minimums of 700 feet given the forecast from the GFA (depicted above). This shows a ceiling height forecast of about 400 feet based on a quick comparison of the color scale for ceiling height at the bottom. This will be evaluated as red and represents a high risk to the flight. The same could be done with your departure and en route personal minimums for ceiling height.

For other variables, such as airframe icing, turbulence, and thunderstorms, you could perform a similar evaluation for the flight using the GFA tool. Airframe icing, for example, could be evaluated based on the probability (percentage) of icing at your proposed cruise altitude and/or the icing intensity (trace, light, moderate, or heavy). Turbulence could be based on the eddy dissipation rate (EDR), so you could set your personal minimums to values you are comfortable with.

For example, if you want to remain clear of any exposure to severe turbulence, set your personal minimum (red) to 36, which is the threshold for the beginning of severe turbulence in a light aircraft. You might set your conservative personal minimum (green) to 16, which is near the threshold where moderate turbulence begins.

If all of your personal weather minimums evaluate to green, then the weather at the time of your departure and while you are en route has met all of your personal minimums with a conservative margin, and you have a low-risk flight ahead of you from a weather standpoint. But what if you have a bunch that evaluate as yellow, implying some elevated risk? This likely means you'll need a “look-and-see” plan before you depart to alter your route, altitude, or destination while en route if the weather is far worse than originally forecast.

The advantage is that you have already determined this action plan in advance based on quantifying that personal risk. Taking the time to set your personal minimums and evaluating those along your route of flight will give you a better grasp of the risk you are assuming. The goal is to avoid any surprises after you depart so you can feel more confident in your plan.

This column first appeared in the December 2023/Issue 944 of FLYING’s print edition.