Transport aircraft are rated for a certain G load that is rarely approached in normal operations. But it is remarkably low, just 2 to 3 G. In an unusual attitude scenario, it is possible to load the airplane much higher, and the danger is bending and/or physically breaking spars and other structural members. Likewise, exceeding Vmax, red line, can also do damage. The jets that hit the WTC were well above red line... damn them for understanding kinetic energy is the square of the velocity. The cockpits were likely squawking like crazy with a thing called an overspeed clacker.
Anyway, after an upset like this, they take the aircraft apart, inspect all of the load-bearing devices, especially the wing spars and the engine struts, magnaflux for cracks, and put everything under a microscope.
These jets are well engineered and can often withstand loads much higher than their rated load. In this case, they found nothing wrong and put it back into service.
I'd guess a 737 could pull 4 G and be fine. 6 G and it'd probably break up. Just estimating.
We had a guy once save his life in an F-15 by pulling 12.5 G to avoid impact with the water, and the jet flew the next day. The same scenario in an F-16 would have resulted in a fatality, due to the G-limiting software. Needless to say, we preferred being in control over the G-available.
Anyway, after an upset like this, they take the aircraft apart, inspect all of the load-bearing devices, especially the wing spars and the engine struts, magnaflux for cracks, and put everything under a microscope.
These jets are well engineered and can often withstand loads much higher than their rated load. In this case, they found nothing wrong and put it back into service.
I'd guess a 737 could pull 4 G and be fine. 6 G and it'd probably break up. Just estimating.
We had a guy once save his life in an F-15 by pulling 12.5 G to avoid impact with the water, and the jet flew the next day. The same scenario in an F-16 would have resulted in a fatality, due to the G-limiting software. Needless to say, we preferred being in control over the G-available.
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