This experiment demonstrates that sufficient pressure was created to reach the failure pressure on SWB3 despite the presence of venting and the failure of the model SWB3 and FS panels...
...A spark was never used to ignite the ¼-scale tests and ignition energy studies were not a part of the ¼-scale testing program. Extensive results are available on ignition energy in separate laboratory tests [Exhibits 20T, L]. The ignition system used in the ¼-scale was actually a hot filament ignition system and no sparks were created.
The problem is that tests on the 1/4 scale model produced, at best, a slowly expanding flame-front (they mention taking several seconds to propagate throug the tank) that, in theory, could have raised pressure to the point you might get structural failure. This is not an "explosion," as normally understood.
Nor was it was ever shown that such a failure would break the nose off the plane - as opposed to, say, blowing out a panel in the tank. They never actually made the 1/4 size model to model structural strength, much less failure modes - just the dimensions. They never got the model to fail structurally. So they are left with saying that they produced enough pressure to, theoretically, make a real 747 fail.
It's not like there is a dire shortage of 747 airframes in which full-scale testing could have been done.
The article is also tendentious about how hard it is to accidentally get an explosive fuel-air mixture. The odds of this happening in the real world could, of course, be estimated by figuring out the full range of pressure and temperature combinations and seeing which are likeliest to occur. Tellingly, they cite data indicating the fuel in a real 747 could have been warm (60C) but no data on whether that would have, in fact, in a real 747, caused an explosive mixture. They were measuring the fuel temperature - odd that they would not measure the fuel in the air in the tank. Perhaps beacuse the odds are astronomically low in the real world, with realistic scenarios.
Good point. A deflagration is not the same as a detonation, and the pressure effects of these are different. (I was a professional engineer before I became a doctor, but I read the article too quickly to pick up on what you are now showing me.)
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I also appreciate what you are saying about the structural strength questions in scale-model testing. They really did need to do full-scale tests, I think. (Interestingly, explosion lab guys should realize this--right?--since structural issues are a big part of what they usually address.)
There was enough at stake in the TWA 800 investigation to warrant full-scale testing.
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I am also surprised by the speculation that the fuel may have been 60 degrees C. That's hot.