June 1, 1997
By Bruce Landsberg
Thunderstorms have always been fascinating topics for pilots, and for good reason. There are three options — learn how to deal with them, ignore them with potentially disastrous results, or stay on the ground whenever they are forecast. The third choice is sometimes a subset of option one, but it means that you won't fly much in the summer since summer forecasts invariably include thunderstorms. As with most weather topics, thunderstorm flying is not easily learned from a book, and many flight instructors take the "just say no" approach — which doesn't help when you're trying to get to Point B.
Last year, the AOPA Air Safety Foundation compiled a major safety review of weather-related accidents that revealed that while thunderstorms may generate a lot of emotional energy, they are not a causal factor in many accidents. Of 5,894 fixed-wing light aircraft weather accidents occurring over the 11-year period from 1982 through 1993, only 3.5 percent — 204 accidents — were caused by thunderstorms. Considering that there are several thousand thunderstorms every day in the United States, it's not a bad record. Apparently, most pilots have learned to respect the power of the force. However, convective weather is a major source of canceled flights, and we don't know how many encounters there were that did not result in an accident but just a good bouncing.
Thunderstorm learning begins in earnest when pilots start to fly real, not contrived, cross-countries. The "warm-up" nature of most private pilot and instrument certificate curricula is not designed to cover the topic in detail. And we haven't devised a practical way to do it because of the nature of weather. It's tough to schedule a thunderstorm when you need one for training, but they're always around when there's some urgency to go somewhere. Limitations of aircraft and self are best learned early because thunderstorm entanglements, when they turn into accidents, are more than twice as deadly as the typical GA accident. Only continued VFR into IMC is worse. In the ASF weather study, 66 percent of thunderstorm accidents involved fatalities.
The best way to learn about boomers is to fly with someone who's been doing it for some time. The airlines and the military have good mentoring systems in which newcomers are paired up with pilots made cautious by experience. Before a new airline pilot gets to make all the decisions, he or she will have been exposed, at minimum, to several years' worth of cumulonimbus. Also available are the tools in the form of full-time dispatchers, good airborne weather radar, and fast aircraft that reduce a 100-mile detour to relative insignificance. Lacking that, GA types will need to learn more carefully.
When I moved from the East Coast to the Midwest 20 years ago, I did not have much convective weather experience, but the reputation of Great Plains storms had been imprinted in my mind by dozens of articles and books. Surprisingly, it turned out to be easier to fly there, where the risk is more obvious, than in the Eastern summertime murk. In Kansas, it's either flyable or it's not — believe it, Toto! In the East there seem to be more borderline situations. Some of the storms aren't as strong, and they hide in the haze while developing. Rule number one is that you must be able to see where the big clouds are — and if you can't, then some substitute for vision is needed, such as weather radar, lightning detection, or a helping hand from outside sources. This means ATC, flight watch, or other pilots.
One learns quickly that forecasts are not guarantees and that storms are where and when you find them. A flexible attitude toward schedule and routing is essential. I prefer to fly earlier in the day because storms are less likely to form in the cooler hours. Pump in a few hours of solar power and a late-day flight is likely to be bumpy. The other major advantage to an early start is that it provides more time to work out alternatives to get to the destination.
Despite that excellent recommendation, several years ago business delayed my departure on a trip from St. Louis to Wichita until just after lunch. The 1965 Mooney M20E was "barefoot," with no electronic storm avoidance gear other than the radio. There was a strong cold front 100 miles west of Wichita but good VFR to the east. An isolated supercell lay across my route, but it was moving northeast along with the strong southwesterly flow aloft. Thunderstorms generally move, develop, and dissipate. This movement means that things will get either better or worse by the time you arrive; and in thunderstorm weather, timing is everything. Arrive too soon or too late and the arrival is likely to be uncomfortable, dangerous, or both. The briefer was emphatic about the potential for severe weather, but there were plenty of alternatives, so it seemed reasonable to start out.
The first two-thirds of the IFR trip was in nearly clear skies with 30 miles' visibility. The big cell had moved north and was dissipating, but when I crossed the Kansas-Missouri border about 40 minutes away from Wichita, the sky became very energetic. Small cumulus were building rapidly into big ones. The bases were about 2,000 feet agl, and the tops were easily 10,000 to 15,000 feet above the Mooney. The prefrontal conditions were exactly as the briefer had described. It was a stimulating environment — very dynamic but with a not-too-subtle hint that things were likely to get ugly later.
The controller confirmed that from what he could see on radar and was able to gather from other flights, there were no thunderstorms between me and Wichita. All the big action was to the west. My assigned IFR altitude was 6,000 feet, but there was so much lift from the growing cloud palisades that maintaining altitude was difficult. I asked for a block altitude of 6,000 to 7,000 feet to provide some cushion and reduced the manifold pressure to 17 inches. Even with the nose level, the VSI would smoothly wind up to show a 1,000-feet-per-minute climb. Then there would be some light or slightly stronger turbulence and a downward trend would begin.
Controlling the aircraft was not a major challenge, but that was only part of the task. Keeping the options open was equally important. How close was the major line of storms to my present position? How close was it to the destination? Where was clear air, if needed? Where was the nearest airport? Should I cancel IFR and go below the cloud bases but give up ATC assistance? There was plenty to think about.
Many thunderstorm encounters do not involve an aircraft's actually getting into the cloud. There can be extreme turbulence on the periphery of storms, as well as strong surface winds. Flying into the cloud itself is a critical and obvious error, but in our cautious approach to learning there is a need to fly in the vicinity of the weather — close enough to get the job done, if possible, but definitely staying out of harm's way. I was clearly in the presence. Runway 19L was in use at Wichita, while the wind blustered from 220 degrees at 23, gusting to 41 knots. Copious quantities of moisture and a major consignment of dust were in the air. Visibility had dwindled to 5 miles, giving the sun and the building clouds a brownish tint. There was not much crosswind on landing, but it was the kind of approach that lobbies for a strong grip on the yoke, positive airspeed control, and power at the ready. The Mooney rolled only a few hundred feet on touchdown.
About an hour and a half later the line came through with all the glory one would expect from such a prelude. Tops of the storms were above 50,000 feet, and several major tornadoes touched down, destroying part of McConnell Air Force Base and a trailer park. The sky and the National Weather Service did a great job of providing a warning, but about 20 people still didn't heed the message.
It was a great trip from which to learn more about thunderstorm flying. There were some prerequisites, though — a good knowledge of where the storms were, the ability to see the clouds, and reasonable proficiency in flying the bumps and handling significant wind on landing. Perhaps the most important, however, was the willingness to change destination or arrival time to avoid the close encounter. There is just no place that you have to be.
ASF's Safety Review, General Aviation Weather Accidents — An Analysis and Preventive Strategies, is available from Sporty's Pilot Shop; telephone 800/SPORTYS (catalog number M904).
See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
Learn to Fly,
Pilot Youth and Introductory,
VFR into IMC,
Safety and Education,
Pilot Training and Certification
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