I swore off this thread, mostly due to an old truism about arguing over the internet that's not fit for mixed company. However, I felt the need to jump back in the fray, because this :
Quote:
|
Originally Posted by willravel
The engines from the plane were the most dense and heavy part of the plane
|
is patently false. The engines, like most the rest of the plane, were designed to be as lightweight as possible. The only exception to that is the landing gear, because it has to withstand multiple impacts against the ground and hold up an object that weighs over a hundred tons (that's short tons, although it also weighs over a hundred metric tonnes if you want to nitpick). In fact, the largest part of the engine is simply a gigantic shroud; the main volume of the engine is all air. It would be oversimplifying to say that a turbofan is just a big kerosene lamp, but probably not by as much as you'd think.
The most dense part of the engine would be either the compressor core or the turbine core; both of them are essentially giant metal cones. These are buried within the engine, underneath the fan shroud and the jet housing - plenty of stuff around them to deform and absorb a nice chunk of the impact energy. I don't know all of the exact details, but I know modern engines are built primarily out of titanium, not for it's strength but rather it's lightness. Titanium is very strong in relatively light quantities, meaning that a titanium engine can be built lighter than a steel or aluminum one. Titanium is also highly resistant to corrosion, which makes it a good choice to extend service life of the engines - the fan blades don't decay like steel blades would, meaning the engine can go longer between rebuilds.
The engines are not the most dense part of the plane. The landing struts are. And we know exactly where the nosegear went, since it punched a nice big hole through three of the Pentagon's rings. I don't know what happened to the two main struts since I wasn't on scene and didn't see any of the debris first-hand, but it's worth noting that they are mounted in the main fuselage under the wing spars. By the time they reached the walls of the building, 100 tons of deforming and disintegrating aluminum and steel in front of them had absorbed the greater portion of the plane's kinetic energy. Just like it did for the engines.