| A plane hitting a normal build does leave debris that can be indentified, because the buildings are fairly flimsy and the plane is hardened in order to stay together during a flight, and the plane and buildings tend to be of different material. A plane hitting the sheer rock of a mountain also leaves debris because there is very little rock to confuse with the plane and the plane is build of differing materials.
A plane hitting the side of a reinforced building is a different matter. Both have heavy structural members and how easy is it to tell reinforced aluminum from reinfored steel? Since the damage is limited to a much smaller area due to the strenght of the building that means that the kenetic energy that is released over time is mush greater. The heat that would be released only several blocks in an urban area, was all released in hundreds of yards. This means that the tempurature reaches were potentially increased by the same factor that the distance was reduced.
So yes, a plane crashing into a city block would create heat ranging up to the heat of the ignited JP4, since the friction heat would be irrelevant. But take a mass the size of the airliner, the velocity (squared, remember) and work out the amount of kenetic enerygy realeased in the crash, then add the jet fuel...and then look at the pictures and notice that the building looks more like it was broiled than burnt. |