Abstract: Aircraft are provided with a perforated blade seal at the lower and/or upper side edges of a control surface contour, such as a flap, with the purpose of acting as a vortex generator, thereby making it difficult for the lower vortex system to move upwards and merge with the upper vortex system. The perforated blade seals are preferably arranged on the inboard and outboard edges of high lift flaps.

Abstract: Flap side edge noise mechanisms have been addressed in a large number of studies during the last decades. A specific vortex system emanates from the flap side edge due to the static pressure difference between the upper and lower flap surfaces. Such pressure difference leads to a merging between the two vortex systems that are generated on the upper and lower edges of the flap side contour. The present invention intends to show the application of a perforated blade seal (21) at the lower (11) and/or upper (8) side edges of the control surface contour, such as a flap (3), with the purpose of acting as a vortex generator, making difficult for the lower vortex system to move upwards and merge with the upper vortex system. The perforated blade seals (21) are preferably arranged on the inboard and outboard edges of high lift flaps (3).