Another issue (that I have some personal knowledge of) is, that once French translations are available, only those are used, and the personnel (not only the pilots) start to forget the international (English) terminology, or at least certainly not keep it up-to-date.
The result in terms of confusion, misunderstanding, incomprehension and outright errors can easily be imagined.
The fact that French is not really a technical language doesn't help matters....
Oh, and another point (again from experience).
Translation is rarely done by people who are also experts in the particular field.
Even highly professional translators rarely know the exact terminology used in a particular industry, or - within that industry - by a particular company.
And since translation is nearly always done as an afterthought, and on the cheap, and rarely closely re-read by the client, some remarkable bludners and erruers do sometimes slip through...
Oh, one more....
Documentation (such as the approach plates mentioned earlier) has this nasty habit of continuously being amended, and evolving over time.
Unless the same organisation that maintains the documentation also keeps the translations up-to-date at the same time, doc and translation soon get out of sync....
Having Air France translating approach plates produced elsewhere is bound to result not only in operational problems, but probably also in legal ones....
Not for nothing does the French BEA state on the first page of their English-language accident reports that the translation is provided as a service, but that the only valid document is the French original.
The same will obviously apply to any English originals translated by Air France... only the original will have legal status.
CJ