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Margins of SafetyMargins of Safety

"Margins of Safety" happens to be the title of the AOPA Air Safety Institute’s new series of short videos on stall avoidance, recognition, and recovery (videos that might just keep a few of your students a little farther from harm’s way if they watch them in time). But it’s also a shorthand way of referring to a concept with implications that extend not only beyond aviation, but also the whole realm of transportation.

At ASI, the subject isn’t new. Recently, though, it returned to our notice as we looked into an entirely reasonable conjecture. In the first years of this century, so-called glass panel avionics quickly took over the new-airplane market with technology that included multifunction displays capable of displaying highly detailed moving maps and even providing terrain warnings. While new production made up only a sliver of the total fleet, the manufacturers and programmers of portable electronics—cellphones, tablet computers, and even standalone aviation GPS units—were quick to emulate the same features, making those potential improvements in situational awareness available to a vastly wider market. Portables likewise emulated and in some cases outpaced panel-mounted avionics in bringing advantages such as back-up instrumentation and even synthetic vision into the cockpit. Available evidence suggests that the flying public enthusiastically adopted them.

It stands to reason, then, that all this additional information would have led to a sharp reduction in controlled flight into terrain (CFIT)—those often-catastrophic accidents in which someone flies a perfectly good aircraft under positive control into a mountainside, radio tower, power line, or bridge. Unfortunately, it hasn’t.

Comparing the 10 years from 1995 through 2004—about the time the most popular portables first came onto the market—with the succeeding decade, the Air Safety Institute found that the overall number of accidents was down, chiefly in proportion to the ongoing decline in flight activity. (The year 2013 was a happy exception to that pattern, as you’ll learn with the release of information on that year in a few weeks.)

However, the number of accidents ending in CFIT didn’t drop nearly as fast, with the result that CFIT actually increased as a percentage of all accidents. This was true in both airplanes and helicopters, and the increases were steeper at night than in the daytime and greatest of all in IMC—exactly the situations where you’d expect improved situational awareness to be most valuable. For example, in the first decade, 4.5 percent of all accidents in visual conditions at night involved CFIT; in the second, that percentage jumped to 6.8. The percentage of fatal accidents in IMC involving CFIT jumped by more than a quarter, from 12.9 to 15.6.

We’ve seen this kind of thing before. The availability of Nexrad downloads didn’t reduce the (already low) numbers of fatal accidents caused by thunderstorm penetration. Instead, any reduction in the number of pilots who blundered into embedded cells seems to have been largely offset by those who erroneously thought they could use those radar images to pick their ways around the edges. (Ongoing public education may be helping in this particular case.) Readers over some particular age—may we suggest 50?—probably need little convincing that before anti-lock brakes became standard equipment on new cars, drivers didn’t tend to follow other cars quite so closely.

What’s at work here is a psychological phenomenon that’s very compelling and almost universal. Because of its power and sweep, those with responsibility for public safety ignore it at their (and our) peril—and unfortunately, that’s what they’ve usually done. Individual tolerances for risk vary enormously, but in familiar situations almost everyone seeks out the point that feels “safe enough.” Once you’re safe enough, why worry about becoming still safer?

The upshot is that technological advantages that could serve to make unlikely but potentially catastrophic events even rarer often serve instead to expand the envelope of things that seem “safe enough” to include circumstances that would once have been considered prohibitive. The effect of new technology isn’t easy to see among pilots who use it to ratchet the accident risk on a flight they would have made anyway from 0.5 percent down to 0.1. Where it shows up in the statistics is among those whose comfort zones it has widened to include conditions they wouldn’t have attempted otherwise. Yes, more flights at the same level of risk would imply that more are completed successfully—but likewise that more end tragically.

David Jack Kenny is manager of safety analysis for the AOPA Air Safety Institute.

ASI Staff

David Jack Kenny

David Jack Kenny is a freelance aviation writer.