CNN has a headline up: Fate or Fluke: Air crash sole survivors. ON the homepage itself the banner reads “Fate or Physics?”
(CNN) — Some will see it as divine intervention, others a simple quirk of fate, fortune or physics, but one boy’s cheating of death in an air crash in Libya this week adds another name to a small roll call of aviation disaster sole survivors.
The boy, identified as Ruben van Assouw, suffered multiple fractures in his lower limbs when the Afriqiyah Airways Airbus A330-200 crashed Tuesday at Tripoli International Airport killing 92 passengers and a crew of 11.
Statistically improbable, the fact of his survival is also unlikely to shed any light on the mysterious factors that increase the chances of escaping alive from a plane wreck.
It’s sort of a fluff piece about a tragedy, but I’m not going to rake it over the coals because honestly it’s not all that bad. Of course I don’t think it’s much of a mystery either – human bodies are all pretty similar in terms of what their structure can endure with regard to sudden deceleration. This is why airplane crashes usually have either many survivors or no survivors. Same thing with, say, car accidents, though the small number of passengers in most cars doesn’t highlight the “most survive or nobody survives” tendency to the same degree.
The list of sole survivors doesn’t appear to be comprehensive, but if it’s representative then it seems to highlight the possibility that the exceptions to the rule are often quite young. If this is a general trend, it may well mean that there is a physics principle behind the unlikely survival of these young passengers. During flight, each passenger is going to have an equal momentum per kilogram by virtue of their all sharing the velocity of the airplane. In a disaster, that momentum is going to be brought to zero by the forces of the crash. If the deceleration is similar for each passenger, then the forces per kilogram are going to be comparable. However, a person’s bone length scales with their height H and their skin surface area scales roughly with the square of their height H^2. But their total mass scales roughly with their volume, which is ~H^3. Thus the ratio of structural support (bones, skin) to vital organs is the highest for lower values of H.
Might this be an explanation for the possible advantage of the young in serious crashes? I couldn’t say for sure, and in any event the advantage may be an illusory effect of CNN’s selection of stories. For that matter I’m afraid it may be in terribly bad taste to discuss this only days after the accident. Still, it’s cold-eyed answers to the questions of physics in airplane tragedies that’s the reason there are so few of them. I hope the investigation into the science of this crash will make such tragedies that much less likely in the future.