To: Togaroo
I quote: “but perhaps the biggest driver for their use is keeping up with the competitor (Airbus) and that their use is more for cosmetic rather than truly performance reasons - i.e. manufacturer seen to be updating a design”.
Boeing designed the winglets used on Airbus aircraft under a NASA contract. The design was offered to Airbus at no cost but if Boeing or anyone else wanted to use them they would have to pay a stiff licensing fee to offset the cost of development. That is why only Airbus uses the design. I can only assume that wing tip sails were installed on Boeing aircraft because there would be some operational benefit and not for cosmetic purposes.
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The Cat