Almost all sector-leading stocks fell Friday, with many reversing lower along with the major averages. Most leaders were still getting support at their 50-day lines. Aircraft components maker TransDigm (TDG) was the only gainer. The Cleveland-based company rose 0.31 to end at 136.88, just off a record high. The stock is extended from its breakout on Aug. 17. But it has found support at the 50-day moving average and may be forming a flat base.