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July 1, 1996
By Bruce Landsberg
If you were going to solve the problem of weather accidents, what questions would you ask? Perhaps you'd want to know what kind of pilot is having accidents in what type of aircraft. What time of year and at what time of day do accidents generally occur? Are thunderstorms and icing major contributors? What is the probability of a fatality? Do wind and low visibility play parts in a significant number of weather accidents? How can pilots learn more to avoid repeating the errors of others?
During the past year the AOPA Air Safety Foundation has learned all it could about the typical weather accident and has produced an in-depth safety review on aviation weather accidents — which is to say pilot misjudgment of weather conditions. Although the review was funded by the Flying Physicians Association, its findings do not shed any light on an old FAA study (1970s) claiming that doctors have more weather-related accidents than do pilots in other occupations. FPA did not buy our silence. The National Transportation Safety Board does not gather any occupation information, so the evidence must remain anecdotal and thus outside the purview of this study. The aviation community owes a debt to FPA for its public spirit in helping ASF tackle a major problem area. Four areas of weather were studied: wind-related accidents, low visibility, airframe and induction icing, and thunderstorms. Over an 11-year period there were 5,894 fixed-wing light aircraft accidents relating to these weather categories. It's a big number, and there is definite opportunity for improvement.
Getting blown off the side or end of the runway on takeoff or landing accounted for 48 percent of the accidents, yet only eight percent of these were fatal. Most occurred between the hours of 9 a.m. and 6 p.m. on Saturdays and Sundays — pleasure flights. Fixed-gear singles accounted for 77 percent of the accidents and, no surprise, tailwheel airplanes were well-represented. Solution — a lot more practice in moderate wind conditions. Pilots need to avoid the really big winds that are beyond the capability of the aircraft and some lesser winds that may be beyond the capability of the operator.
In fatal weather accidents, of which there were more than 1,700, VFR-flight-into-instrument meteorological conditions was the leading cause. Thirty-six percent of these accidents occurred at night, which is far out of proportion to the amount of night flying. The night bogeyman is real, and he hooked VFR and IFR pilots alike. Clouds are harder to see, as is terrain, and weather reporting is sometimes not as good. There is more fog at night because temperature and dew point get closer together.
Probing the VFR-into-IMC accident more deeply, we found that 82 percent were fatal, making it the most deadly weather accident. Weekends had the poorest record, indicating that personal fliers had far more trouble than business pilots during the week. Two-thirds of the pilots had received weather briefings generally indicating that VFR was not recommended, and nearly 80 percent shunned a flight plan of any kind. This seems to indicate that the weather was not a surprise in most cases — and the risks taken were deliberate. Very few of these accidents occurred on landing — the flights never made it that far. Most were lost en route, although nearly 15 percent either crashed on takeoff or during initial climb, where the danger was obvious before ever leaving the ground.
One unexpected finding was that weather-related precautionary landings, while usually resulting in significant damage to the aircraft, frequently saved the occupants. If the pilot admitted that he was in trouble and then actively attempted to get the aircraft on the ground, under control, the results were far better than if he became disoriented in the clouds.
Every pilot has a fascination with thunderstorms, and at least 200 pilots got too close to cumulonimbus. Sixty percent of these accidents occurred in cruise flight and, not surprisingly, during the summer months. Familiarity does seem to breed contempt, because the largest category of pilots had more than 1,000 hours total flight time. What the accident investigations don't tell is how many times the pilot had pulled the tiger's tail before getting mauled.
The next largest category involves relatively low-time pilots with between 100 and 500 hours total time. Perhaps a slightly mangled cliche applies: What you don't know certainly can hurt you. Our bet is that these pilots were just starting to stretch their cross-country wings and failed to understand the danger. When only three percent of weather accidents involve thunderstorms, we can feel reasonably certain that only a few brave and ignorant souls are trespassing on Thor's turf. Don't stop planning those avoidance strategies, however.
Airframe or structural icing is listed in only slightly more accidents than thunderstorms. And again, like thunderstorms, this is mostly an experienced pilot's problem. We suspect that some pilots are exploring the winter clouds and that most of the time they get away with it. But airframe ice is insidious and forecasting it is not easy. Temperature, cloud structure, air mass moisture content, and airframe shape all play a part that has confounded our ability to predict accurately where and when it will be a problem.
While we're on the subject of icing, remember an old nemesis — carburetor icing. Every student learns about using carburetor heat early in training, but somewhere along the way the lesson is forgotten. It's still a significant problem and something that CFIs should cover on all flight reviews. Pilots used to flying high-performance aircraft models have to be extra careful when flying carbureted engines on smaller aircraft, since fuel injection essentially solves the problem, and they may have forgotten the need for heat. Better yet — we should start replacing all carbureted engines with fuel injection. That probably won't happen on my watch, but the technology certainly exists.
The FAA and NTSB probably do as good a job as time and money allow in investigating light aircraft accidents, but examination of the human factors aspect is lacking. Far too much effort is spent sifting through the aluminum and not nearly enough on the faulty decision process. For this reason, a landmark VFR-into-IMC accident report involving a business jet is included in the review. It is one of NTSB's best human factors investigations in recent memory involving a non-air carrier accident. After reading this, it's tempting to wonder why we aren't doing more debriefing on the lower profile accidents. Rhetorical question — time and money, of course.
In addition to a comprehensive statistical review that will appeal only to accident junkies, there is a "quick look" for the pilot who just wants an overview. The review has more than 100 weather case studies — accident briefs relating locations, pilot experience and ratings, aircraft types, and a narrative of what went wrong. There is a complete section on winter flying that includes icing, lake-effect snows, and learning how to deal with the winter winds. Also included in the review is information about thunderstorms, low visibility, and air stability, as well as a pilot's approach to forecasting. Risk management suggestions, a checklist to prepare for adverse weather, and a training syllabus to avoid weather mishaps are also a part of the publication. Finally, there are reprints of some of the best weather articles in AOPA Pilot.
Pilots who fly more than just locally on good VFR days will find that this is an excellent investment. For CFIs it is essential. Sooner or later every pilot encounters significant weather, and the record shows that our training and mentoring system needs tweaking. This report provides a unique insight into perhaps the most vexing judgment problem facing general aviation.
General Aviation Weather Accidents: An Analysis and Preventive Strategies is available from Sporty's Pilot Shop for $24.95 by calling 800/SPORTYS (800/776-7897). Ask for catalog number M904A.
See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
Safety and Education,
Pilot Training and Certification,
VFR into IMC
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