We had just mounted the booms on a 280' self support. At that time we were doing a very unsafe practice at a former company I used to work for. It was getting dark and my job Foreman rode up on the winch line. He stoped at my elevation, 250', and told me to hurry hanging the stiff arms he was going up to re-rig for the morning of running the lines. That's exactly what he did. The wind was gusting up to 30 MPH, he got to the block, tied off and called for slack on the ground. He took the block off the tower and and switched it to a different leg. He did this without changing the position of the heal block to save time. So the down line was going across the face of the tower. He came back down to 250' and told me to hop in the line by getting in the choker under him. He was riding the mollyhogan. I reluctantly agreed when I was in the line we called for a cable down. I knew something was wrong at that point. I felt the cable rubbing bad. I looked up at him asked what was going on he said it was fine. What he did not realize was when he called for the slack this allowed the down line to wrap around the tower to a site below us. After decending about another 10' - "SNAP" - we fell rapidly. I was grabbing at every peice of steel I could. When I finaly grabbed on, my foreman was in my lap. He grabbed onto the tower and I struck down a few feet and lanyard off. About that time the winch line made it thru the top block and came down whipping down and taking a piece of my ear with it. Then the jerk of the line took my foreman down again the only thing saving him was my lanyard on the tower and us being connected by a choker. He got himself back on the tower. we were aprox. 50' from the tower base. So many things could have taken us down all the way. Only a few saved our lives. My advice to anyone after this experience. Don't ride the line! If you are pressured, say you would rather climb down. Saving a few minutes almost cost my life; definitely not worth it. I was only a year in the business and I trusted my foreman knew what he was doing.