Riblets: Ready for application on next generation aircrafts?

Riblets are streamwise grooved surfaces able to reduce the skin friction in turbulent regime. Despite they have been successfully tested even on large commercial aircrafts, they have never been introduced in practice. However they are still the only passive drag reduction system which has the potentiality to be introduced in next generation air transport. In present paper the reasons why they still have not been adopted are discussed. In addition, it is described how we are trying to overcome the actual show stoppers drawbacks within Clean SKY 2-GRA research Program. Efforts have been undertaken in Manufacturing technology, Theoretical and Experimental Aerodynamics.