Tim pointed me at the video of the test run for evacuating the A‑380 — it’s worth a look. I noticed, however, that it wasn’t exactly a very realistic test. If you read the page rather than just leaping to the video, you’ll see the discussion of an earlier MD-11 test where a woman over the age of 45 tripped and fell; bear that in mind when you watch the A‑380 evacuation video.
What struck me about the video was that the evacuation was not only carried out in ideal conditions, but the participants were also all ideal. All between the ages of roughly 20 and 45, all wearing comfortable trousers, none of them overweight, none of them carrying or cajoling children or babies, none of them in wheelchairs or connected to oxygen supplies, none of them in high heels or flimsy dresses (or good suits, come to that). All were fit and able to jump on the slide without hesitation. In a plane carrying over 850 people, what proportion will be in some way encumbered, and how big a difference does that make to the evacuation?
In a lot of ways the video reminded me of the films that are always being shot around Vancouver. One I saw being shot at Vancouver airport had lots of extras towing bags around pretending to go somewhere and looked unrealistic for the same reasons — no-one was overweight, or elderly, or had babies or children, unlike every airport I’ve been to recently.
Hmm, yes, so they use fit people. The rules for certification just define a time for the evacuation trial and a basic mix of ages, sexes, etc. As programmers our first thoughts could be how much more complicated the rules would have to be if they had to specify a mix of unfit/incapable people. You’d need all sorts of rules about who sits where and so on which would have be applied sensibly for an A380 or a little commuter plane.
E.g., suppose you said that some percentage of the people had to have a body-mass index over a certain amount. Some very fit athletes are technically obese by this definition because the simple BMI doesn’t take into account the difference between fat and muscle. An aircraft manufacturer might go along to the local football or rugby clubs looking for “overweight” people to join in the trial.
Also, there’s a small but real risk of hurting a few of these more-capable people in an evacuation trial — consider how much more risk exposure there would be in the trial if a realistic mix was required. (Ordering an emergency evacuation of an airliner is one of the harder decisions a captain is likely to have to make — knowing that quite likely some people will be hurt, perhaps seriously, in the process).
Overall, I think it is better to compare aircraft designs using reasonably fit people for the evacuation trials and just assume that in an actual emergency a certain factor would have to be added to the total time.