Flaperon separated at altitude
I'm told “derive plonge entre deux eaux” literally means drifted plunged between 2 waters.
Not sure what this means literally. Something lost in translation for sure. Anyway, I have worked with honeycomb and carbon fiber structures (spacecraft) and I see no way for water to enter a structure constructed like the flaperon, unless the bonded skin on one or both sides was nearly 100% removed, leaving all the cells open to the water. The flaperon recovered at Reunion shows relatively little damage to the skin on both the top and bottom surfaces. The net boyancy should be a few hundred pounds. Nor is there any evidence in the photos of compression damage which would occur if the flaperon was deeply submerged.
The photos are most consistent with right flaperon separation at some altitude above the water, before the main structure impact, most likely caused by buffeting, aeroelastic flutter, or transonic aeroelasticity, all of which can ultimately result in the type of fatigue failure which appears to be the cause of the trailing edge separation. There are many documented cases of aircraft components “shaking loose”, caused by these phenomenon when the aircraft exceeds the certified speed. Put this historical and engineering fact together with (1) the final BFO values, which taken at face value indicate a vertical descent speed of 15,000 ft/min at 00:19:37, accelerating downward at 0.68Gs and (2) the B777-200 ER simulator results which indicate a steep, high speed spiral descent is very likely following fuel exhaustion (and no human control), and all the puzzle pieces fit.
This theory, if true, increases the likelihood of the main POI being quite close to the 7th arc. It sure would be nice to hear something official about the internal examination results. Unless virtually all the honeycomb cells were full of water, there is no way this flaperon could sink or float near neutral buoyancy.
Note: If the flaperon broke loose at some altitude above the water, it would float down like in the air like a leaf, with almost no impact damage. It is very light compared to the surface area. This has nothing to do with the speed at which the remaining structure hit the water, which could have been near Mach 1.