Nobody thinks much about aircraft escape slides unless and until they’re needed. And then they think about little else. If an airliner itself is a technical marvel, one of the sub-marvels aboard is the slide system. Every exit door has to have one and in a big airframe like the 777, there may be a half-dozen, including complex models that have to fold down over the wing for evacuations from mid-fuselage. An Airbus 380 has 16. In this video posted by Alex Warren, you can see a selection of slides being deployed for routine testing and maintenance.
Modern slides are required to deploy within six seconds in winds up to 25 knots and are required for every exit where passengers can be expected to egress without injury. They’re not used often, but they’re not rarely used, either. In the 10-year period between 1990 and 1999, the NTSB found that 27 incidents and 21 accidents required evacuation and use of slides. Call that about five times a year.
And sometimes they don’t work. Or they don’t work as expected. A subsequent report by the NTSB found that in seven out of 19 evacuations reviewed, at least one slide failed to operate correctly. Sometimes, they inflate uncommanded, as on this United Airlines flight in which an aft slide inflated, momentarily alarming passengers seated near it. That sort of thing happens about three or four times a year, although rarely inflight. Usually, the fault is human error. And to minimize that, flight attendants double-check that the slides are disarmed at the gate. When you hear the call to “cross check,” one attendant is making sure another deactivated the slide. It gets really messy if one lights off at the jet bridge.