The Administrative Director shall be head of the Department of General Administration and shall be possessed of executive and administrative qualifications in municipal government.  In order to serve effectively as Acting Mayor when required to do so by Article IV, Section 3 of this Charter, he shall, under the supervision and control of the Mayor, be charged with general supervision of the administration of the affairs of the City.  He shall perform, in addition, such specific duties as may be required of him by the Mayor or the Council.