TWO MEMBERS WERE AT THE TAIL LOADER AREA ON LW15 PREPARING TO SPLICE A PUMP CABLE. THE VICTIM, UNDER SHIELD #176, WAS BENT OVER TOWARD THE TAIL ENTRY LOOKING FOR A CABLE CRIMPER WHEN A ROCK FE LL FROM THE ROOF AND STRUCK THE EDGE OF THE ROCK GUARD AND BROKE IN TWO. THE MIDDLE PIECE (63"" X 15"" X 14"") ROLLED OVER INTO THE WALKWAY AT #176 AND STRUCK HIM. HE WAS FLOW TO THE HOSPITAL.