Rule 100¹²³
Examination of appeals

(1)¹²⁴ Unless otherwise provided, the provisions relating to proceedings before the department which has taken the decision impugned shall apply to appeal proceedings. 

(2) In the examination of the appeal, the Board of Appeal shall invite the parties, as often as necessary, to file observations, within a period to be specified, on communications issued by itself or observations submitted by another party. 

(3) If the applicant fails to reply in due time to an invitation under paragraph 2, the European patent application shall be deemed to be withdrawn, unless the decision impugned was taken by the Legal Division.