The pilot of a hospital medical helicopter and two nurses are dead after the chopper went down about 94 miles west of Chicago yesterday.  The FAA says last night's crash occurred while the helicopter was heading to pick up a patient in Mendota after taking off from Rockford.  The hospital identified the occupants as pilot Andy Olson and flight nurses Jim Dillow and Karen Hollis.  The chopper crashed in a corn field in the small town of Compton, near the city of Rochelle and was destroyed.  No patients were aboard at the time.  The helicopter had been registered to Rockford Memorial Hospital.  The aircraft had taken off from Rockford which is 25-miles north of the crash site.  A team from the FAA will assist in an investigation of the crash, which will be led by the National Transportation Safety Board.