Originally Posted by booskins
Can someone please tell me the technical reasoning behinf the 777 not having winglets. They fly a long way and I want to know why thaey are not used and if anyone thinks that winglets will be fitted to existing 777 in the future, like the A320 which is being tested with winglets. Are the gates/vortex generators really that effective on the 777 stopping the span wise flow.
Winglets are only really benneficial on long haul flights. Winglets themselves add extra weight and drag to the aircraft which have their obvious penalties, and on short flights they don't earn their keep! But when used on a long flight, then efficiency bennefits outweigh the drawbacks.
All wings have spanwise flow. The idea of winglets is to remove the drag inducing vorticies away from the main wing reducing the downwash effects. You'll note on the ER 777's and on the 767-400ER, a "Raked Wingtip" has been used instead which basically results in the same thing (reducing wingtip vorticies). A raked wingtip means that the wing tip is highly swept.
The 777 wing is quite different to your standard airliner wing. It has a "super critical" wing design and is many years ahead in its efficiency.
So RWT's for the 777, winglets are out!
767-400ER with raked wing tips (RWT's)
777 with RWT's
