Boeing has developed a solution to curtail the buffeting of the inboard flaps of the 747-8F at the maximum flap.
The final fix, which resulted in a modification of the outboard main landing gear doors, puts the lower panel of the door more in line with the upper panel, which was previously rigged at a 45° angle similar to preceding 747 variants. The modifications also include vortilons on the inboard flap as well as a bullnose design on the leading edge of the upper half of the outboard landing gear door.
The buffet was first experienced when the aircraft had its gear down and flaps extended to the 30 position. Pilots reported a "very apparent" vibration that was eventually traced to the outboard landing gear door. The issue was revealed following the first flight of the 747-8F in February, later validated by RC522, the second test aircraft to fly, as a design issue.
The 747-8F features an all new super critical wing design with the original triple slotted inboard trailing-edge flap system succeeded by a simpler double-slotted design.
Source: Flight International