YAKOVLEV HAS BEEN FORCED TO MODIFY the prototype Yak-130 advanced jet trainer, following early test flights which revealed problems with the winglets. Sources close to the programme say that the winglets were found to be "deforming" As a result, they have been removed, and the aircraft has since been flown with conventional wing tips. The company is understood to be intending to strengthen the winglet and to continue flight trials with the reinforced version.
Source: Flight International