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Why the Boeing 787’s Engines Feature Chevrons While the 777X’s Do Not

Why the Boeing 787’s Engines Feature Chevrons While the 777X’s Do Not
When the Boeing 787 Dreamliner and 747-8 entered service in the early 2010s, their distinctive engine nacelle chevrons—saw-tooth serrations along the trailing edge—were widely regarded as a significant advancement in noise reduction technology. Developed with support from NASA, these chevrons were engineered to smooth the mixing of hot engine core air with cooler bypass air, thereby reducing turbulence and, importantly, jet noise. This innovation enabled the Dreamliner to meet stringent International Civil Aviation Organization (ICAO) and airport noise regulations, making it particularly well-suited for operations at noise-sensitive airports.
However, as Boeing prepares to introduce the long-delayed 777X, the new GE9X engines powering the aircraft notably lack chevrons. This absence reflects a shift in industry thinking: what was once considered a groundbreaking, standard-setting technology now appears to be a niche solution rather than a universal design feature.
The Benefits and Drawbacks of Chevrons
Chevrons primarily serve to reduce engine noise by breaking up turbulence at the engine exhaust. Both engine options for the 787—the General Electric GEnx and Rolls-Royce Trent 1000—incorporate chevrons, as does the GEnx variant used on the 747-8. By mitigating noise, chevrons help airlines comply with strict noise regulations and facilitate operations at airports with stringent noise limits.
Despite these advantages, chevrons come with several trade-offs. They introduce additional aerodynamic drag, which slightly reduces propulsive efficiency. Furthermore, chevrons add structural complexity and weight to the engine nacelle and can complicate maintenance procedures. For manufacturers, the decision to include chevrons depends on whether the noise reduction benefits justify these penalties.
Since the Dreamliner’s introduction, neither Boeing nor Airbus has incorporated chevrons on their latest aircraft models. The Boeing 737 MAX, Airbus A350, A330neo, and A320neo families, as well as Pratt & Whitney’s PW1000G-powered jets such as the Embraer E-Jets and Airbus A220, all omit chevrons. This industry-wide trend suggests that, beyond the Dreamliner, the trade-offs associated with chevrons have not been deemed worthwhile.
The 777X: A Different Approach
The Boeing 777X, which is poised to enter service after several years of delay, continues this trend by forgoing chevrons on its GE9X engines. This design choice reflects a broader consensus within the aerospace industry that the drawbacks of chevrons outweigh their benefits for most new aircraft designs. With the 747-8 now out of production, the 787 remains the only current commercial aircraft featuring chevrons.
Complicating the 777X program further, Boeing and GE Aerospace are investigating a potential durability issue involving a seal in the GE9X engine. Despite this challenge, Boeing maintains that the issue will not affect the 777X’s anticipated 2027 delivery date. The aircraft, however, remains six years behind its original schedule and is still awaiting Federal Aviation Administration (FAA) certification.
Looking Ahead
While chevrons continue to be a defining characteristic of the 787, their absence on the 777X and other recent aircraft models signals a shift in design priorities. As manufacturers strive to balance noise reduction, fuel efficiency, and maintenance considerations, chevrons appear to be a specialized solution rather than an emerging industry standard. Meanwhile, Boeing emphasizes safety and operational resets, with the market maintaining confidence in the company’s long-term prospects despite ongoing certification and engineering challenges.

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