An employee was servicing an aerial drop. He set up his ladder, ascended to about 18 feet, and secured himself to the strand using his body belt and safety strap. As he started working, his ladder began to slide to the right. He began descending the ladder to readjust it. As he was descending, the ladder slid again to the right, causing him to fall off the ladder from about 14 feet. He landed on his feet on the street and fell backwards, breaking his left heel and several bones in his right foot.