Abstract: AT APPROXIMATELY 8:00 A.M. ON FEBRUARY 5, 1990, EMPLOYEE #1 WAS DESCENDING THE LADDER FROM THE COUNTER JIB TO THE CAB OF A POTAIN G3/28B U.S. HAMMERHEAD TOWER CRANE. EMPLOYEE #1 HAD BEEN ASSISTING A MECHANIC IN PERFORMING SOME MAINTENANCE REPAIR ON THE COUNTER JIB AND THE MECHANIC HAD PRECEDED HIM DOWN THE LADDER A SHORT TIME BEFORE. THE MECHANIC HAD APPARENTLY LEFT THE HATCH OPEN AT THE BOTTOM OF THE LADDER. WHEN EMPLOYEE # 1 GOT THERE HE STEPPED OFF, EXPECTING THE HATCH TO BE CLOSED. HE FELL THROUGH THE OPEN HATCH APPROXIMATELY 8 FEET TO THE PLATFORM BELOW, SUSTAINING A 4-INCH LACERATION AT THE TOP OF HIS LEFT BUTTOCK. HE WAS TRANSPORTED TO THE HOSPITAL WHERE HE WAS TREATED AND RELEASED. THE MAIN CAUSAL FACTOR WAS EMPLOYEE #1'S APPARENT FAILURE TO CHECK TO SEE WHETHER THE HATCH WAS CLOSED PRIOR TO DESCENDING THE LADDER TO THAT LEVEL.