(Added by Ordinance No. 135664, effective Dec. 6, 1972.) Unless specifically provided otherwise by ordinance, in the absence because of illness, disability, vacation or leave of absence, and upon resignation, retirement or discharge, of the chief of any bureau or office, whose duties are general by virtue of that position, his chief assistant or deputy shall serve as acting chief and perform the duties of chief without additional compensation, until the Council, the Commissioner In Charge or the superior official in charge directs assigns or otherwise or a permanent successor is designated and takes office.