I read an article about the test Boeing and NASA did in 2005 the QTD2 on a 773 with GE engines. It had chevrons on the nacelle and exhaust cone, the 787 with GE and RR engines only have chevrons on the nacelles and the 747-8 with genx2 has them on both nacelle and exhaust cone. What would be the reason for this? Is there a drawback to have chevrons on the exhaust cone? As genx1 and 2 is almost the same engine it is odd IMO.
Will this go on the 777X?