39 C.F.R. § 4.2
The Vice Chairman is elected by the Governors from among the members of the Board and shall perform the duties and exercise the powers of the Chairman during the Chairman's absence or disability. The Vice Chairman is elected at the Board's regularly scheduled annual meeting for a term that commences on December 1 of the calendar year in which the election occurred or upon the death, departure or resignation of the current Vice Chairman, whichever occurs first, and expires upon the election and installation of a successor Vice Chairman. In the event of the Vice Chairman's death, departure or resignation prior to the election of a successor, the Board, as soon as practicable, shall elect a new Vice Chairman who shall serve a term that commences immediately upon election and expires upon the election and installation of a successor Vice Chairman.
39 C.F.R. §4.2