Good point, Rok... but it doesn't help your case. The last transponder return is the last time we know for certain that TWA800 was still operational. The next beep that should initiate a return would not occur for ~4.8 seconds... the initiating event MUST occur sometime in that gap. No matter when it did occur, it shortens the amount of time for any zoom climb to occur before splashdown.
Now my reading of the radar data seems to indicate a slight slow down of the aircraft... 376Knots to 359Knots while the next two subsequent returns calculate to increases. This slight loss of airspeed (17 knots) is consistent with the loss of engines power which were countering drag and a small climb (we could calculate this out but why bother) as the aircraft trades velocity for altitude. The subsequent returns are consistent with the aircraft accelerating to terminal velocity in a ballistic fall and coincide with a parabolic arc down to the sea.
Strangely enough (or perhaps not so strangely) this seems to coincide completely with the time line I outlined in post #192.