While preparing to teach a full day of radar training to an association of owner-operator pilots this past June, I was asked to review eight convective weather-related accidents that had occurred in their make/model of aircraft, the earliest of them occurring in 2003, the latest in 2018 (so recent the NTSB Final Report has not yet been released). The request was for me to find one or two that would be an interesting “case-study” for the group. After reading each of the reports, I concluded the best path forward was to present a glaring commonality they each shared.
For context, seven of the eight were “loss of control” accidents resulting in fatal injuries to all on board. While all three people involved in the eighth accident survived, damage to the aircraft was extensive enough the NTSB classified it as an accident. The most revealing commonality with each was associated with a significant “non-radar” clue. To properly set the stage, a couple basic concepts should be reviewed first.
First, airborne weather radar should be considered a moisture, or precipitation detector, not a thunderstorm detector. In fact, radar does not distinguish between stratus and convective precipitation; that delineation is solely a pilot responsibility. This is just one of many limitations airborne radar brings to the equation. A strength, however, is that it provides a real-time image of the detectable precipitation. In contrast, NEXRAD is amazing technology but attempting to use it as the sole technology to navigate or thread through an area of convective weather is a catastrophic mistake. NEXRAD employed properly with a full understanding of its limitations coupled with airborne weather radar makes for a powerful team.
Second is the responsibility pilots inherit when they earn their certificate with respect to risk management; this is a significant obligation. Risk-analysis is not a black-and-white matrix, but specific to the individual pilot. It is based on obvious elements, such as weather conditions, but also includes pilot experience, knowledge, proficiency and fitness to fly (i.e. rested, focused and prepared) as well as aircraft equipment/configuration.
Before each flight my risk assessment (whether as pilot-in-command or as a passenger in the back, as happens to be the situation as I author this) begins with a review of the Convective Outlook (www.spc.noaa.gov). A detailed explanation for this chart can be found at the website as well as AC-0045H. But, in short, it inventories the atmosphere and then annotates areas where the chances of general thunderstorms are less than 10 percent, greater than 10 percent, or various probabilities of severe convective weather.
Note, this is not an aviation-specific chart, but a chart used by a wide spectrum of people responsible for keeping the general public safe. You’ll see your favorite news channel refer to it often. The individuals who produce this chart from their specialized cell in Norman, Oklahoma, are among the most talented of professionals; the accuracy of their final product is always impressive. The chart does not imply the entire area will be saturated with that weather. The related risk potential is valid within 25 miles of any point in the designated area (in pilot-speak, about three to eight minutes flying time depending on aircraft type and operating speed).
Over the years I’ve gained great confidence in this chart as a discriminator for what type of precipitation is likely to be encountered or detected with radar during the flight in that area. Precip detected while departing from a field, transiting through or arriving to an airport within one of these areas (greater than 10 percent or any risk of severe weather) should be assumed to be convective (even if not meeting the criteria for a thunderstorm) with all the associated hazards until established otherwise. It’s also common for pilots to complain of a choppy ride when cruising through these areas. Don’t be surprised if the controller reports that all pilots at all cruise altitudes are experiencing a similar ride. Go figure—the atmosphere is churning.
Once at the SPC site, select the Convective Outlook. There are three associated charts, each with its own specific value to the individual user. In addition to the Categorical, I always refer to the Hail chart, which provides a percent risk of hail in the designated area(s). The decision to operate in any area containing hail potential should be a deliberate risk-management decision. The atmosphere is volatile; operating in proximity to any significant cells in these areas risks a hail encounter. The other two charts are the Wind and Tornado charts.
The boundaries between these areas (including less than and greater than 10 percent chance of thunderstorms) warrants a brief discussion. Think of the boundary between these areas as similar to the boundary between fast- and slow-moving water in a stream—there is potential for some chaos. If the boundaries are compressed tightly together, watch out—it can be a downright nasty ride, even if no storms are present.
One important comment about the white areas of the Categorical chart: It means there is less than a 10-percent chance of thunderstorms, but it does not mean a 0-percent chance; thunderstorms can still develop. In all the cases of convective-related incidence and accidents I’ve looked at, I’ve seen it once (NTSB Accident Number ERA11GA066). While there are no doubt others, they are the exception.
So let’s get back to the owner/operating group and their eight accidents. The commonality each accident shared is that each of them occurred in or on the boundary of one of these areas. This is not to say something bad will always happen to a pilot if operating in one of these areas, but if something bad related to convective weather does happen, it is virtually guaranteed to be in or on the boundary of one of these areas.
The Convective Outlook for each of the eight accidents were extracted from the archives. The red star annotates the approximate location of each accident. Note that all of the accidents occurred in or on a boundary of an area highlighted by the Convective Outlook.
What does this mean to you for any flight if the departure or arrival field is contained within one of these areas, or if transiting en route? Make a conscious, risk-management decision that you are willing to accept the risks associated with the potential of that area. Following are a few important considerations.
The Terminal Aerodrome Forecast (TAF) is required to be reviewed for each flight. However, the geographically valid area is one of its most significant limitations as the TAF is valid only for a very small area surrounding the airfield. The TAF alone, while required, is insufficient; other weather charts must be consulted during preflight planning. The Convective Outlook is a great place to start.
If feasible, consider choosing a route that completely circumnavigates these areas as skirting just outside a boundary won’t likely yield the desired result. If your destination is within an area highlighted by the Convective Outlook, keep a close eye on the forecast as it will be amended frequently if weather conditions within that small area start to change.
If your destination falls in an area of greater than a 10-percent chance or there is any risk of a severe storm, always plan an alternate. If possible, choose an alternate where there is less than a 10-percent chance of thunderstorms. For purposes of fuel planning, don’t plan on being able to get to that alternate in a straight line. In other words, when the weather begins to build in these areas, it will often do so violently and rapidly. At this point, expect competition for the radios; you will not be the only one with a weather problem. You should also anticipate being put in queue for your IFR clearance to the alternate, no doubt watching nervously as the remaining fuel reserves deplete.
You should anticipate that conditions in these areas—even in clear air—may exceed the capability of the autopilot. Be prepared to go old-school and hand-fly the aircraft. This has happened more than once where the pilot found they were in a situation exceeding their piloting-skills.
Tragically, another convective weather-related fatal accidents occurred within their aircraft make/model since the group met this past June. Unfortunately, the pilot had not attended the day-long airborne weather radar training program held during the June conference. We didn’t judge the decisions of the pilots of the previous accidents during the program, but we did capitalize on the lessons learned. Predictably, the accident occurred in an area highlighted by the Convective Outlook. While the NTSB final report won’t be available for a few months, it is safe to say the information offered by the Convective Outlook highlighted the associated risk, and in-turn had the potential of preventing the accident.
If you’re thinking springtime might be better timing for this discussion, remember it’s always thunderstorm season somewhere. And, some of the worst weather I’ve ever encountered (embedded thunderstorms) was in the LA basin in the winter. Start now to get in the habit of including the Convective Outlook in your preflight planning.
Erik Eliel is a line pilot for a major U.S. airline who also conducts airborne weather radar training programs for airline, military, and general aviation pilots. The website for his company, Radar Training International, is http://www.rtiradar.com/
