The Unit Trust of India Act,1963
Section 15. Casual vacancy in office of Chairman or executive trustee
If the Chairman or the executive trustee is by infirmity or otherwise rendered incapable of carrying out his duties or is absent on leave or otherwise, in circumstances not involving the vacation of his appointment, the Reserve Bank may nominate another person to act in his place until the date on which the Chairman or the executive trustee, as the case may be, resumes his duties.