Emergency airplane evacuations happen more often than most people think: about once every 11 days in the U.S., according to a 2000 report by the National Transportation Safety Board. Some situations are more dire than others, of course, as when the plane is on fire, but in many cases, the biggest challenge of an evacuation can be the airplane slide.
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Last week at Heathrow Airport, when 136 passengers had to get off a British Airways Boeing 777 that had crashed short of the runway, they did it by escaping down the eight slides unfurled at the plane's exits. The deplaning, like the landing itself, was very successful, with no fatalities and only a handful of injuries.

The investigation won't be done for months, but it is likely that some of those injuries happened during the evacuation — not the initial crash. Even in controlled drills, accidents are common. When the new, supersized Airbus A380 underwent mandatory evacuation tests in 2006, 33 of the 873 evacuating volunteers got hurt. One suffered a broken leg, and the remaining 32 received slide burns. And that was considered a success.