Below are some pictures of various fixed wing aircraft with winglets. It is widely accepted that these winglets will improve an airplane's performance by reducing drag and therefore improving fuel efficiency.
Here is also an official video of Boeing 737 Max that is being tested in Boeing's trans-sonic wind tunnel. In the video, it is claimed that the addition of the split winglet will reduce drag and improve fuel efficiency.
Airbus also said the claimed the same in regards to their A380. It has a claimed 4% efficiency improvement from the addition of a winglet.
But now, Boeing is developing a new airplane which with "foldable" wing, the 777x. The wing is "foldable" to accommodate taxiway width limitation of some airports. Clearly, it is not because of aerodynamics. But at the same time, Boeing claims that it will improve efficiency up to 7%.
Then my question is, if using a traditional winglet will increase the aerodynamic as well as fuel efficiency, why does Boeing not implement this for the B777x?
- Picture 1: Boeing 777x with folded wings.
- Picture 2: Boeing 777x with straight wing.
- Picture 3: Boeing 737 Max with Y-shape winglet.
- Picture 4: Boeing 747-400 with bent-up winglet.
- Picture 5: Airbus A380 with Y-shape winglet (like Boeing 737 Max).