A selection board shall consist of five or more officers who are on the active-duty list of the same armed force as the warrant officers under consideration by the board. At least five members of a selection board must be serving in a permanent grade above major or lieutenant commander. The Secretary concerned may appoint warrant officers, senior in grade to those under consideration, as additional members of the selection board. If warrant officers are appointed members of the selection board and if competitive categories have been established by the Secretary under section 574(b) of this title
, at least one must be appointed from each warrant officer competitive category under consideration by the board, unless there is an insufficient number of warrant officers in the competitive category concerned who are senior in grade to those under consideration and qualified, as determined by the Secretary concerned, to be appointed as additional members of the board.