Why do some turbofan blade have forward swept tips? I notice that in Trent700  engine fan blade there is no curve extension at the tip unlike in other engine's fan blades such as the GE90 ,T900 etc. 

What are the purpose of it?




Trent 700 without forward swept blade tips




Engine with forward swept blade tips
Increasing performance of the fan means making it rotate faster. Tips of the fast-rotating fan travel at supersonic speeds. This design of fan blades is to overcome blade stall and to increase effectiveness of the fan. The design is probably patented and that's why it doesn't show up on engines of other manufacturers.