In my area the UIC (me) is responsible for organizing the umpires, ensuring certifications (if necessary) are in order, scheduling (some areas have separate schedulers), fielding questions, complaints, etc from other board members (in my case, 4 league presidents and 4 player reps (these
PR's are the people that players can go to with ANY problem anonymously, whether with a coach, the league, umpires, whatever ... 1 per league), as well as the district director (soon to be me as well)). The UIC is also responsible for training their umpires and holding clinics. I'm sure there are other duties out there that other UIC's do (or some that I do that I may have forgotten about). I also attend the tournaments to rule immediately on any protests or rules problems.