You may have noticed the saw-tooth design on the exhaust nozzles of Boeing’s 737, 787, and 747-8 engines. In contrast, this design is absent from any of Airbus’s latest aircraft. These saw-tooth exhaust nozzles play a crucial role in reducing engine noise. However, chevrons found on Boeing engines may be obsolete as new engine noise reduction technology continues to evolve.
These chevrons are only found on Boeing planes, the 737 MAX, the 787, and the 747-8. However, they are no longer found on the newer 777X. Here’s why.
To understand the importance of chevrons in jet engine design, it’s essential to see how they help in noise reduction. Chevrons are specialized aerodynamic features integrated into aircraft nozzles to manage and lower noise levels during operation.
Chevron nozzles direct airflow as it exits the bypass duct. The pointed sections of the nozzle are strategically positioned to guide the airflow, preventing the rapid mixing of high-speed and low-speed air. This controlled airflow significantly reduces noise, eliminating the need for heavy insulation on the engines.
Some advanced aircraft designs utilize double chevron nozzles, which feature chevrons for both the airflow from the combustion chamber and the bypass duct. The alternating arrangement of these pointed sections helps to keep the airflows separate, minimizing the chances of turbulent mixing that can increase noise.
Chevrons Do Have Disadvantages
The Boeing 747 is a prime example of double chevron innovation. This design enhances the aircraft’s aerodynamic efficiency and supports quieter operation, making it more environmentally friendly and compliant with airport noise regulations. Overall, these chevrons demonstrate how engineering continues to evolve, improving performance while reducing environmental impact.
However, there are some drawbacks to chevrons found on Boeing planes. They can lead to decreased thrust and efficiency because they create vortices that drain energy from the engine. While this reduction may be acceptable during takeoff, it becomes less justifiable during cruising.
Airbus has consistently opted not to use chevrons on its engines. Meanwhile, Boeing seems to be moving away from chevrons in its GEnx engines as well. It is reported that General Electric has been developing a new technology for the past 20 years that could eliminate the need for chevrons. They introduced an oxide-oxide ceramic matrix composite in October 2013. However, this will also require a combination of a new exhaust nozzle design to reduce drag and technology to lower cabin noise. The Boeing 777X is expected to utilize this technology.
The Boeing 777X and its GEnx engines are still awaiting certification, meaning this new noise reduction technology has yet to be tested. While Airbus has never employed chevrons, it appears that Boeing may have found ways to reduce noise without them. So, are the chevrons on Boeing planes about to become obsolete? Although the 737 and 787 are still in production, any changes may not occur immediately—potentially with future iterations of these aircraft. The situation for the 777X will likely be different.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
