Boeing Drops 777X Chevron Tech, Aligning with Airbus's Noise Feature Omission
Boeing has discontinued the use of chevron engine technology, previously seen on its 787 Dreamliner, 747-8, and 737 MAX aircraft, with the introduction of the 777X. This change follows Airbus's consistent decision to omit the noise-reduction feature from its own new aircraft models, suggesting a broader industry consensus on the trade-offs involved.
Boeing Departs from Chevron Engine Design with 777X
Boeing has ceased incorporating chevron technology into the engines of its latest aircraft, the 777X, marking a significant shift from its earlier designs. Chevrons, characterised by their sawtooth-edged nozzles, were a feature on the Boeing 787 Dreamliner, 747-8, and 737 MAX models, primarily implemented to reduce engine noise.
However, the 777X, rolled out in 2019, does not include these structures, despite earlier conceptual renderings that often depicted them.
This departure aligns Boeing with other major aircraft manufacturers, including Airbus, Embraer, Irkut, and COMAC, none of whom have adopted chevron technology on their contemporary aircraft such as the A330neo, A320neo, A350, A220, E-Jet, MC-21, or C919. This suggests a re-evaluation of the technology's overall benefits versus its drawbacks across the aviation sector.
NASA's Pioneering Work in Noise Reduction
The development of chevron technology originated from research conducted by NASA, which began flight testing experimental jagged-edged nozzle engines in 2001 using a modified Learjet 25. In 2025, NASA published an article titled "NASA’s Chevron Technology Quiets the Skies," highlighting the innovation's role in lowering noise levels for communities near airports.
NASA researchers discovered that rectangular notches, or tabs, used by the military to disguise jet fighter infrared signatures, could also reduce engine noise by facilitating the mixing of hot air from the engine core with cooler fan bypass air.
Early tests by NASA found that chevron nozzles achieved a notable decrease in noise, comparable to the difference between operating two lawnmowers versus one, with a negligible thrust reduction of 0.25%.
Rationale for Initial Adoption and Identified Drawbacks
Boeing initially adopted chevrons for its 787 Dreamliner, with the technology later applied to updates for the 747-8 and 737 MAX. Aviation commentator Petter Hörnfeldt, in a video published eight years ago, explained that chevrons reduce engine noise by controlling vortices created by exhaust and bypass air.
These small vortices help create a boundary layer, capable of reducing takeoff noise by up to six decibels, which is significant for meeting noise regulations around certain airports and flight paths. Hörnfeldt also noted that quieter engines can allow for the removal of some heavy insulation, leading to minor weight reductions and improved aerodynamic efficiency.
However, he clarified that chevrons are not inherently aerodynamic and cause a small thrust reduction, estimated at approximately 0.5%, by diverting energy from the main vortex generation.
Industry Shift Towards Alternative Noise and Efficiency Solutions
The widespread omission of chevrons from new aircraft, including Boeing's 777X and all modern Airbus models, suggests that the perceived benefits of noise reduction no longer outweigh the associated thrust penalty. While GE Aerospace has not publicly detailed its reasons for dropping chevrons, it is plausible that advancements in engine design have rendered them redundant.
Contemporary extra-high bypass engines, such as the GE9X, combined with improvements in fan blade aerodynamics and the use of composite fans, are likely quiet enough to meet current and future noise regulations independently.
This allows manufacturers to prioritise fuel efficiency, as engines without chevrons can achieve better fuel burn due to the absence of the minor thrust reduction. This evolution in engine technology drives a focus on optimising aerodynamic performance and operational costs for airlines globally.
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