Wx Watch: Storm Warnings

For the past few months, I've been steadily chipping away at mountains of data, creating a new AOPA Air Safety Foundation safety report. Due to be published in May, the report will address the role of adverse weather in general aviation accidents. The report contains a few surprises and identifies some weather phenomena as major accident-causers — phenomena that you might at first blush think were not particularly dangerous.

However, an examination of 11 years' worth of thunderstorm- related accidents confirmed conventional wisdom. No doubt about it, thunderstorms kill. In the study period — from 1982 to 1993 — there were 204 accidents in which thunderstorm activity was named as a cause or contributing factor. In 77 percent of the cases, or 157 accidents, there were injuries. The fatality rate was 66 percent, meaning that of the 157 injury-producing wrecks, 135 involved one or more deaths.

With all the warnings drummed into our heads from day one of our training, do you ever wonder how it is that pilots continue to come to grief in convective weather?

The short answer is that they appear to do it by using two main methods. They either press on into areas of confirmed thunderstorms, or they try to continue flying VFR into worsening weather.

These seem to be errors of hubris or phenomenal stupidity. How in the world can pilots justify flying toward storm cells? The answers are few, given that so many thunderstorm accidents are fatal.

It's certainly not that they've been given bum steers by flight service. Incorrect forecasts were named as causes or factors in a mere handful of cases (fewer than 15) in the entire 11-year, 5,894- accident pool of weather-related crashes — and none of them had to do with thunderstorms. So these pilots learned about thunderstorms — or their likelihood — during their preflight briefings (62 percent obtained weather briefings), then flew on anyway, knowing what awaited them. As for the 32 percent for whom there's no record of a weather briefing, what can you say?

When it comes to those who attempt to continue VFR into instrument weather, their motivation must also remain in the realm of speculation. Perhaps these pilots had flirted with instrument conditions before and always managed to skirt or penetrate areas of cloud and precipitation successfully — if illegally. It worked before, these pilots may reason. Why should today be any different?

Or it may be that some pilots, having never had the experience of flying in marginal weather, didn't fully comprehend how quickly clouds can close up, how an enticing cloud-free corridor between towering cumulus can turn into a dead end, or how disorienting and frightening an inadvertent entry into dark, turbulent, rain-producing clouds can be — particularly at night.

Lack of experience flying in adverse weather certainly plays a part in thunderstorm accidents. In 10 cases, the NTSB ruled that pilots without instrument ratings or instrument experience were to blame for continuing VFR into IMC. Eight other pilots, with "limited instrument experience," were blamed for in-flight airframe failures after attempting to traverse convective weather VFR.

Does having an instrument rating inoculate pilots against having thunderstorm accidents? No way. But experience flying in actual instrument conditions made a big, big difference in the statistics.

Get a load of this: 29 percent of all thunderstorm accidents involved pilots with fewer than 10 hours of actual instrument time, 41 percent had fewer than 50 hours of actual, and 51 percent had fewer than 100 hours of flight in the soup. Big deal, you may say. That just means that the other half had more than 100 hours of actual and therefore was equally represented in the crash figures.

Not really. First of all, in 32 percent of the thunderstorm crashes there's no record of the pilots' actual instrument hours. According to statistical convention, however, we can assume from the size of our sampling that the "unknowns," if plotted, would very closely match the distribution of actual instrument times that are recorded; i.e., more accidents for the under-50-hours-of-actual crowd. Second, the evidence that nearly one-third of the pilots in thunderstorm crashes had fewer than 50 hours of actual — by itself- -should make us all stand up and take notice. Experience flying in the soup is a huge safety advantage.

Then there's the other end of the pilot experience spectrum. Here we have instrument-rated, high-time pilots obviously trying to wend their way past thunderstorms, many of them almost certainly attempting to duplicate similar successful past efforts. Forty-six percent of thunderstorm accidents involved pilots with instrument ratings, and 40 percent of pilots had logged more than 1,000 total hours.

This gives us evidence that the highly touted benefits of experience can backfire. Instead of extensive flying experience's instilling a heightened sense of caution, the reverse may be true for a select few. For those pilots who like to live on the edge, many past successful encounters with bad weather may serve to embolden. "Been there before," the high-timer may muse during the weather briefing. Then he launches. In this formulation, the pilot's thinking parallels that of the habitual scud runner who may not be instrument-rated, may disdain filing IFR if instrument-rated, and may even skip a briefing altogether.

There's still another reason why some pilots come to grief in convective weather. Weather conditions are volatile in unstable air, and sudden changes can and do occur. It's possible for the most diligent of pilots to become trapped in developing thunderstorms — particularly if they're flying in instrument conditions where thunderstorms are embedded in the surrounding clouds. Early in the day, based on atmospheric soundings, meteorologists and briefers may mention the possibility of convective activity later on. In the morning a pilot may make a perfectly safe departure in VMC, then run into a worsening convective situation with a subtle progression from scattered to broken cumulus, to towering cumulus, to complete envelopment in cumulonimbus clouds. Sometimes these situations are just plain bad luck. Most of the time, however, there is adequate warning that things are going sour. But first you have to be able to recognize the signs.

It takes time for pilots to become weather-savvy. Good judgment, an aptitude more difficult to quantify than hours flying on instruments, is another essential to safe weather flying. If the statistics prove anything, it's that experience and caution are the two most valuable commodities a pilot can cultivate when flying in thunderstorm season.

To build up these strengths, be diligent. If you don't have an instrument rating, pursue this training. It will improve every aspect of your flying and is the cheapest insurance you can buy when you're beset by rotten weather. Once you've earned the rating, file IFR often and make your immersion into actual conditions a gradual one. Robert Buck, author of the classic book Weather Flying, suggests that newcomers to instrument flying start out by flying from good conditions to good conditions, with light instrument weather (no icing, thunderstorms, or wild fronts) confined to the en route phase. Then comes a period of exposure during which Buck recommends flying from instrument weather at or near the departure airport to improving conditions. Ultimately, the instrument pilot advances his seasoning by flying from good conditions to progressively worse weather at his or her destinations.

In thunderstorm season, let caution be your guide when judging the weather and determining plans for storm avoidance. There are no hard and fast rules, of course, but the following makes good, reliable advice for both VFR-only and instrument-rated pilots:

• Fly early in the day. Thunderstorms intensify with the heat of the day, and peak convection usually occurs between 3 p.m. and 8 p.m.
• Obtain a complete preflight weather briefing. Ask for the latest convective outlook (AC in weather abbreviation-speak), radar summary, satellite information, live radar imagery, and pireps. Note the issue times for any radar summary charts. These can be several hours old by the time you see them.
• En route, be prepared to execute a 180-degree turn should the weather deteriorate.
• Stay visual. In this way, you can see buildups in their formative stages and avoid potential trouble spots.
• Don't allow yourself to be forced into climbing on top of rising cloud layers. Soon you may find yourself engulfed in building cumulonimbus clouds. Then there's no way out but to descend — through potentially hellish conditions.
• Keep up with weather trends via flight watch and any ATIS, AWOS, or ASOS broadcasts at airports along your route.
• File IFR if instrument-rated. If not, use flight-following services from ATC. Though provided on a workload-permitting basis, flight following can be an invaluable, ready source of advice, assistance, and emergency help should events warrant. For VFR-only pilots, flight following is the next best thing to filing IFR.
• If equipped with radar or lightning detection devices (either a Stormscope or a Strike Finder), be sure you understand their limitations and correct use. The radars used in smaller general aviation airplanes are subject to attenuation, which can make the radar display screen show misleading and dangerous false radar returns. Lightning detection devices, especially the older models, often depict lightning returns at inaccurate ranges. This pseudoranging portrays stronger, faraway lightning strokes as closer to the airplane; and the weakest, farther away. The truth may be that you're flying very near some weak — but still very respectable — convection that's soon to build.
• Night flying deserves special mention, particularly in mountainous terrain. Cloud avoidance is more difficult, and terrain clearance will become a major concern should turbulence compromise your ability to maintain altitude.
• Don't press on in worsening conditions, justifying your decision based on an absence of convective sigmets. These may be issued only after pilots report trouble with building cumulus or outright thunderstorms. By the time you hear of any sigmets, you may have your hands full dealing with turbulence and precipitation that didn't exist 20 minutes ago — trouble you could have avoided by turning around.
• Don't succumb to get-home-itis. The statistics suggest that many weather accidents occur on weekends. It's a safe bet that many pilots were determined to fly to their vacation spots or to make it back home. The weather must have been a secondary consideration.
• Last, but certainly not least, make it a point to spend some time just looking at the sky, every day. Time watching The Weather Channel and other sources of near-real-time weather radar is also time well spent. Over time, you'll gain a sense of what's about to happen without any major clues from flight service. You'll also realize that it doesn't take a doctorate in meteorology to know that a thunderstorm is about a half-hour away.

With enough observations like this, you should be able to take a rudimentary intuition into the cockpit when you fly. A half-hour is a long time in an airplane. Long enough to recognize a storm situation (assuming you've followed the rule about staying visual), turn around, flee, land, and tie down in good VFR if it's daylight. Too bad some pilots don't seem to have that intuition.