EMPLOYEE HAD MOVED TO FACE SIDE OF LONGWALL FACECONVEYOR WHILE CHAIN AND FLIGHTS WERE BEING MOVED BY MEANS OF HYDRAULIC TENSION UNITS. A SLAB OFCOAL APPROX. 4' X 2' X 8"" FELL OUT FROM THE FACE ONTO EMPLOYEE, PUSHING HIM INTO PANLINE. EMPLOYEE WAS SUB-CONTRACED TO LONG AIRDOX FOR REPAIR WORK TO FACE CONVEYOR.