The head of city hospitals got a 20% raise last year just a few months before Mayor Bloomberg signed off on a nearly $1.3 billion bailout for the cash-strapped system. Alan Aviles, president of the Health and Hospitals Corp., earns $351,062 annually under a three-year contract the system's board approved in January 2010. That makes him Bloomberg's highest-paid appointee, dwarfing the $250,000 salary of Schools Chancellor Cathie Black and the pay for top cop Raymond Kelly, whose salary was bumped to $205,180 last year. The HHC, which controls 11 hospitals, four nursing homes and dozens of community clinics, argues it is a public corporation that can't be compared with city agencies. It also says private-sector hospital presidents earn far more than Aviles, pointing out that the head of New York-Presbyterian Hospital makes more than $9 million a year.