5.1.5.What is the language of the proceedings in the European phase? 

5.1.013The language of the proceedings is one of the official languages of the EPO (English, French and German). If the international application was published by WIPO (see point 3.2.027) in an official language of the EPO, that language is the language of the proceedings in the European phase. If not, the EPO official language of the translation to be submitted upon entry into the European phase is the language of the proceedings (see points 5.5.001 ff).

5.1.014The EPO does not allow the language of the proceedings to be changed. Reference is made to decision G 4/08 of the Enlarged Board of Appeal.