Abricot:
As a French native speaking, I feel that the key sentence in the BEA report is quite odd, grammatically incorrect. In contrast the rest (whole) of the document is quite well written and clear.
"l’avion a vraisemblablement heurté la surface de l’eau en ligne de vol, une forte accélération verticale." would translate as "the plane likely hit the water surface 'en ligne de vol', a strong vertical acceleration". (sic)
Again as a native French speaking it sounds like the author was not confident in this specific phrase or didn't understand what (s)he was writing.
Maybe you should get back to the hard facts (splatten things photos) and disregard this particular odd sentence.
Hi,
Sorry but no. Be sure they do know exactly what they were talking about and this "little syntaxical blunder" (a comma instead of a coordination agent) may be explained if the text was edited at the last minute. Either they removed something in the description of the impact, either they added the last part of the sentence ("une forte accélération verticale).
S~
Olivier