Why assume an initial damage to the fuselage, as in Fig.15? It has much to do with the structure, where the strongly built center wing penetrates a fuselage. This means that the fuselage has a cutout, which weakens it.
There is certainly a strong connection between the center wing and fuselage, quite sufficient for normal loads. However, such construction performs much worse in the case of impact loads that are associated with the explosion. This reasoning could be countered by saying that during landing such shock loads are present, and the designer was aware of that. However, we are dealing with a fundamental difference: The landing loads press the fuselage against the wing, while the impulse from the wing attempts to separate the two.
The loss of leading edge at the fuselage and partial separation of the wing give two important aerodynamic effects: loss of lift on the left wing and an increase in aerodynamic drag. The first one causes rotation around the longitudinal axis, while the second forces the plane to turn left. Figure 16 shows the continuation of rotation and the wing segment left further behind.
Figure 17 illustrates the fragmentation of the fuselage after the internal explosion, described below.
The internal explosion in an already pre-damaged hull, in the presence of a still active torque causes the separation of the two parts. The front of the fuselage continued to rotate around the longitudinal axis, but only because of its inertia. The rear part is still "driven" by the uneven distribution of lift on the wings. This results in mutual rotation of these components so that the end of their relative position, as shown in the figure, is similar to what was found on the crash site.
It is not important whether the angle of rotation of each of these two parts was exactly a multiple of 1800. It is enough if the rotation angle exceeds 900, and as a result of inertia of the center wing, an upside down landing of rear portion is enabled.
Speaking of the final location on the ground, the front part of the fuselage finally stopped at the approximately normal position. The rest of the machine was hitting the ground in the upside - down position and undergoing further fragmentation. Finally, parts of the center wing stopped near the cockpit after assuming an inverted position.
A more detailed fragmentation pattern is shown in Figure 21, as created by Mr. Marek Dabrowski, MSA. Since this was created independently, not all of the details described here coincide with the above sketches.