Tuesday, March 22, 2005

Experiment Design

I guess my laboratory career left me interested in the process of designing experiments to answer a question of interest. An article in the Wall Street Journal today suggested and discussed an interesting one. A European consortium is building a very large passenger plane called the A380 which can be configured to carry 853 passengers. It would take 1 hour to get all these people on board, seated and buckled in. In case of an emergency, it will be required that the Airbus builders demonstrate that all of these passengers can be evacuated through blankets and baggage scattered about the cabin as it would be following an accident. In addition, only 1/2 of the 16 exits would be available....in the dark. Because the plane has a second story, some of the passengers will be required to find their way to the exit and jump into space, land on a steep inflated slide and avoid pilling in a heap at the bottom of the slide. As for additional requirements, 40% of the test passengers must be female, 35% must be over 50 years of age, and 15% must be both female and over 50. Some of the females will be given dolls to cradle in their arms and take with them through the evacuation. In order for the airplane to be certified for commercial use, the evacuation must be completed in 90 seconds.

I see this as a situation where the demonstration could easily be gamed by selecting certain individuals who will not freeze at the top of the 2nd story slide, will maintain poise and calm at the exits rather than pushing others aside. In a previous experiment with another plane everyone performed well under ordinary conditions. The results were quite different when the participants were offered added financial awards depending on the speed at which they exited. It got kinda rough at the exit doors according to the reports. In some previous tests of other planes, the passengers are given helmets and have their ankles taped to prevent injuries. This could be because one 60 year old lady caught her foot in the slide, flipped and went down the slide head first. When she hit the pile of people at the bottom of the slide she broke her neck and has been paralyzed ever since.

I am sure the engineers will eventually be able to get the plane certified to operate in every country which requires such tests, but I am also sure if you are in a plane crash the evacuation will in no way resemble any of the tests and you should not get on the plane if being able to get out in 90 seconds is important to you.

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