I mean worst as in furthest from reality.
This is my pick, from the description of the impact damage to the South Tower:
“There was heavier damage to the 79th floor. The left engine and the inboard section of the left wing shattered a 25 ft. wide section of the center of the floor slab all the way to the core of the building and severed 15 perimeter columns. Reaching the building core, the debris severed nine columns, heavily damaged another, and abraded the SFRM from the eastern two thirds of the columns and trusses all the way to the north end of the core.” page 40/90
http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdfThe debris severed nine core columns? Is this claim credible?
When the aircraft hit the perimeter wall, how come part of the wings severed the perimeter columns, but part of the wings were diced by the perimeter columns?
NIST conducted component impact analyses and found that “The impact of the inner half of an empty wing significantly damaged exterior columns but did not result in their complete failure. Impact of the same wing section, but filled with fuel, did result in failure of the exterior columns.” page 107/157
When the left wing (or bits thereof) hit the core columns, it was less likely to sever them than the perimeter columns, because (1) it weighed less because the fuel had flowed out, (2) it had already suffered mechanical damage after impacting the perimeter, (3) impacting the perimeter columns must have slowed it down, (4) the core columns were tougher than the perimeter columns.
What about an engine? Could the left engine have come through the perimeter wall and severed the core columns?
NIST also performed simulations to check whether an engine could sever one or more core columns:
“Moving at 500 mph, an engine broke any exterior column it hit. If the engine missed the floor slab, the majority of the engine core remained intact and had enough residual momentum, to sever a core column upon direct impact.” page 107/157
It appears that United 175 was moving at 500 mph, but did the engine miss the floor slab?
The description quoted at the start (“The left engine and the inboard section of the left wing shattered a 25 ft. wide section of the center of the floor slab”) indicates that it did not. Further, the impact damage diagram on page 39/89 shows the engine hitting the floor slab smack in the middle. It is therefore unlikely that the engine core had the speed or mass to sever a core column, even had it scored a direct hit. Even if it did have them, it would have had to ricochet around the core several times without losing much momentum to score the required nine direct hits. This is somewhat farfetched.
Indeed, the figure of nine severed core columns on floor 79 is so far removed from a reasonable estimate (zero severed core columns on this floor) that I am almost moved to speculate that it is not the product of computer modelling, but that lead NIST investigator Shyam Sunder retrieved it aurally.
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