EVERETT- Boeing’s long-awaited 777X program is nearing certification, with the fourth test aircraft already airborne. The company aims to deliver its first Boeing 777-9 to Lufthansa (LH) by 2026 from Frankfurt Airport (FRA).
However, Lufthansa and other future operators won’t see one design feature initially proposed— “Engine Chevrons”. Once part of the 777X concept, the serrated-edge nacelle design was removed during development and will not be part of the final production aircraft.
Photo: GE AerospaceBoeing 777X Dropped Engine Chevrons
Engine chevrons, those jagged “teeth” at the rear of jet engine nacelles, were originally planned for the Boeing 777X, just as they had been implemented on the Boeing 787 and Boeing 737 MAX.
The concept aimed to reduce engine noise by smoothing the interaction between hot exhaust and cooler bypass air.
However, despite being featured in early renderings, Boeing ultimately dropped chevrons from the 777X design.
According to Simple Flying, the change was driven by new developments. Instead of using chevrons, Boeing and General Electric employed a new low-drag, low-noise nozzle on the GE9X engines.
Terry Beezhold, the 777X chief project engineer, confirmed this shift, stating that the nozzle redesign achieves similar acoustic performance while offering better aerodynamics and lower weight.
In addition, advancements in materials, particularly ceramic matrix composites, enabled internal noise reduction techniques.
GE and Safran integrated honeycomb acoustic treatments and strategically perforated composite skins to capture and reduce sound more efficiently than chevrons, and without the associated drag and thrust penalties.
Photo: Huy Do | JetPhotosEngine Chevrons Role
Engine chevrons were developed in collaboration between Boeing, NASA, and GE. These serrated structures were introduced as part of Boeing’s Quiet Technology Demonstrator (QTD) initiatives.
First seen on the 787 and then adopted by the 747-8 and 737 MAX, they effectively reduce fan tone noise by up to 15 decibels during takeoff and landing.
The mechanism is straightforward: chevrons help mix hot and cold airflows more smoothly, reducing turbulence and therefore noise.
However, they introduce a small aerodynamic penalty, resulting in a roughly 0.5% reduction in thrust.
While this trade-off was accepted on earlier aircraft, newer materials and internal noise suppression methods offer better solutions for the 777X.
The Boeing 787 and 747-8 both feature chevrons on their General Electric GEnx engines. Rolls-Royce Trent 1000-powered 787s also use them.
The Boeing 737 MAX, with its CFM LEAP-1B engines, includes nacelle chevrons as part of its noise mitigation strategy.
However, Airbus has generally avoided the technology. The A350, for instance, uses alternative acoustic treatments within its nacelles and relies on ultra-high bypass engines to manage noise.
Engineers cited marginal benefits and potential fuel penalties as reasons for not adopting chevrons, along with Boeing’s now-expired patent on the design.
Photo: FRAME | YouTubeGE9X Engine
The GE9X engine, developed exclusively for the 777X, has undergone rigorous testing, including high-stress “triple red line” conditions where it achieved a record 134,300 lbf of thrust.
While this exceeds typical operating levels, it signals exceptional power and reliability for the aircraft.
Designed with fuel efficiency and noise reduction in mind, the GE9X uses fewer fan blades, advanced materials like ceramic composites, and optimized internal acoustics.
Each engine is estimated to cost $45 million, making it the most expensive commercial engine to date.
With Emirates (EK) ordering 205 777-9s, the GE9X’s success could redefine noise-reduction standards in next-gen aircraft.
Photo: By Dan Nevill from Seattle, WA, United States – 20190313_085824, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=77445932New Approach to Noise Reduction
With the 777X, Boeing has shown that innovation doesn’t always mean more complexity. By abandoning chevrons in favor of advanced internal treatments and redesigned nozzles, the manufacturer achieved equal or better acoustic performance with fewer aerodynamic penalties.
This shift also reflects broader industry trends toward integrated, low drag solutions over add-on structures.
The evolution of the 777X highlights how aircraft design is driven by both performance metrics and operational economics.
In this case, what was once considered a cutting-edge external feature has been replaced by smarter, internal solutions that meet modern acoustic and efficiency demands.
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Boeing 777X Advances Certification with Crosswind Testing
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