PPRuNe Forums - Raked Wingtips vs winglets

Sometimes we accept too uncritically what the manufacturers say and reporters report. Not that long ago in discussion with one maker he asserted that fuel consumption would improve by 14% at one remove thanks to new wing technology.
On closer analysis what emerged was this. Option 1 was increased wing area and wing span leading to a 2% improvement in L/D at one spot on the curves. From 16.0 to 16.32 by memory but improved engine economy permitted M0.78 instead of M0.74 for the same fuel flow so that although L/D had gone up by only 2% the product ML/D had improved by 7.5%. Next, Option 2 was to add fancy wing-tip treatment which improved L/D to 17.28, an increase of a straight 8%, again for that one spot on the curves. But by comparing ML/D for M0.78 with ML/D for M0.74 there was the hyped 14% increase in “efficiency”. All well and good but 6% of this was thanks to better engines, quite a lot to do with less induced drag associated with a better aspect ratio and only some to do with airflow at the wingtip. From a sales point of view the impression was meant to be that it was all down to the fancy wing-tip technology that the other guys did not have. Some of this was true but a few critical minutes writing an Excel spreadsheet took the lid off the tin. My guys went and bought that aircraft anyway but the choice had a lot more to do with all the other factors in operating and financing an airline. Decision made that was not how much of the press saw fit to report it. But when you sup with the devil always sup with a long spoon. I’m not saying for or against tip technology. Just beware the salesman’s statistics and partisan "My dad's bigger than your dad" views. I am more than happy to receive the paycheck and fly whatever.