Decibels For 0.5% Thrust: The Engine Trade-Off Boeing Made & Airbus Refused

Boeing’s engine chevrons—those sawtooth edges on several Boeing nacelles—are more than styling. They are chevrons developed from NASA research to reduce noise when hot jet exhaust mixes with surrounding air. Boeing applied the concept to aircraft including the 787 Dreamliner, 747-8 and the 737 MAX family, accepting a small aerodynamic penalty for a quieter departure footprint. NASA flight testing showed meaningful noise reductions, while industry assessments placed the thrust penalty at roughly a 0.5% reduction. The article contrasts this with Airbus, which did not pursue the same approach across its latest commercial engine families, instead moving toward quieter internal engine architectures, such as the GE9X on the 777X, which has no visible chevrons.