From ASRS Callback
The problem this Maintenance Technician reported provides a dramatic lesson in
the need to
verify proper setup before going ahead with a job, especially one
I was assigned to work at jack point “E” at the left-hand, inboard side of the B777 wing. At the site, I found that the jack pad [adapter] was already installed and the jack was seated with 4,000 LBS of pressure on it. When all the jacks were in place, my Lead instructed me to start jacking and he left the site to check on the right wing jacking area. I started jacking by increasing the pneumatic pressure to 7,000 LBS. As the jacking process was going on, my fellow Mechanic, who was on the wing dock at the jack point, heard a cracking noise and saw the panel cracking. He yelled at me, “Stop!” I immediately stopped the jacking process. I went up on the left-hand wing dock and found out that the [wing] panel underneath the jack pad was damaged. Afterwards we learned that the day shift had installed the jack pads backwards.
involving high-pressure jacks.