Article 43

1. The seniority of chairpersons and members shall be calculated according to the date on which they took up their duties as specified in the instrument of appointment or, failing that, as fixed by the Management Board of the Office. Where there is equal seniority on that basis, the order of seniority shall be determined by age. Chairpersons and members whose term of office is renewed shall retain their former seniority.

2. Where the chairperson of a Board of Appeal is prevented from acting, that chairperson shall be replaced, on the basis of seniority as determined in accordance with paragraph 1, by the most senior member of that Board of Appeal, or, where no member of that Board of Appeal is available, by the most senior of the other members of the Boards of Appeal.

3. Where a member of a Board of Appeal is prevented from acting, that member shall be replaced, on the basis of seniority as determined in accordance with paragraph 1, by the most senior member of that Board of Appeal, or, where no member of that Board of Appeal is available, by the most senior of the other members of the Boards of Appeal.

4. For the purposes of paragraphs 2 and 3, chairpersons and members of the Boards of Appeal shall be considered to be prevented from acting in case of leave, sickness, inescapable commitments and exclusion pursuant to Article 169 of Regulation (EU) 2017/1001 and Article 35(4) of this Regulation. A chairperson shall also be considered to be prevented from acting where that chairperson acts ad interim as President of the Boards of Appeal pursuant to Article 47(2) of this Regulation. Where the post of chairperson or member is vacant, their respective functions shall be exercised ad interim pursuant to the provisions in paragraphs 2 and 3 of this Article concerning replacement.

5. Any members considering themselves prevented from acting shall without delay inform the chairperson of the Board of Appeal concerned. Any chairpersons considering themselves prevented from acting shall without delay inform simultaneously that chairperson's alternate determined in accordance with paragraph 2 and the President of the Boards of Appeal.