The Boeing 747-8 family's flap configuration is one of the new variant's key aerodynamic changes, while the shape and design of the landing gear doors was carried over from previous versions. Unlike early 747s, which have inboard and outboard triple-slotted devices, the -8's outboard flaps are single-slotted and the inboards are double-slotted.

The earlier configuration allows turbulent air to pass through whereas the single and double-slotted flaps provide "a lot more surface to cause a turbulent layer to form", say programme sources.

Unexpected structural buffet can be common during flight testing, although the solution may vary from vortex generators to redirect the airflow or even a complete redesign of the disruptive part.

Source: Flight International