Why Boeing 737 MAX Engine Covers Are Serrated

One way you can tell the Boeing 737 MAX from its non-MAX sisters is by the ‘teeth’ on the rear of its engines. These are also found on Boeing’s other latest-generation jets, such as the 787 Dreamliner and the 747-8. But why are they there?

Boeing 737 MAX, Serrated Engine Covers, Noise Reduction
The Boeing 737 MAX has a serrated edge on the rear of its engines. Photo: Getty Images

The Boeing 737 MAX is set to resume passengers flights above the United States later this month following 20 months of grounding. This time next year, the serrated engine covers of the 737 MAX will become a much more common sight at airports around the country. Let’s find out more about these ‘teeth.’

Developed with NASA and others

The real name for these teeth on the engine’s nacelle, or engine cover, is chevrons. However, to learn why they’re used, let’s first discover where they came from. Boeing first trialed the Chevron design on its second Quiet Technology Demonstrator.

Stay informed: Sign up for our daily aviation news digest.

The technology was developed by Boeing, General Electric, and NASA, and initially also saw chevrons placed on the engine exhaust nozzle in addition to the nacelle. While the 747-8 has both sets of chevrons, the 787 and 737 MAX only have the nacelle chevrons.

Boeing 737 MAX, Serrated Engine Covers, Noise Reduction
Chevrons were first trialed on Boeing’s second quiet technology demonstrator. Photo: Boeing via NASA

Reducing noise emissions

The chevrons’ aim on the engines of newer Boeing aircraft, such as the 737 MAX, is to reduce the noise made by the aircraft’s engines. In the words of Boeing,

“The chevrons reduce jet blast noise by controlling the way the air mixes after passing through and around the engine.”

Indeed, the chevrons are so effective at reducing noise that in 2005 Boeing estimated that they would allow several hundred pounds of sound insulation to be removed from the aircraft. A lighter aircraft is a more fuel-efficient aircraft. Meanwhile, the reduction in noise generated by the aircraft will surely be greatly welcomed by residents living near the world’s busiest airports.

The future…

Interestingly, the chevron engine nacelle design found on the 737 MAX, 747-8, and 787 isn’t found on the American manufacturer’s latest aircraft. The 777X doesn’t have the chevrons on the massive GE9X engines that power it. As technology has continued to evolve, it seems that Boeing has achieved the same result with new technology.

Boeing, 787, ecoDemonstrator
Boeing has continued testing how to make aircraft quieter with its 787-10 ecoDemonstrator. Photo: Paul Weatherman via Boeing

However, Boeing is continuing its work to make its aircraft quieter and more efficient. Recently, it used a Boeing 787-10 bound for Etihad in its ecoDemonstrator program. As a part of the tests, Boeing was looking at technologies to reduce further the noise generated by its aircraft.

One of these ideas saw aerodynamic covers placed on the aircraft’s landing gear. An aircraft’s landing gear accounts for 30% of the noise generated as an aircraft comes to land. While Boeing is still crunching the numbers, witnesses said that the aircraft with the modified landing gear was noticeably quieter.

Have you flown on an aircraft with chevrons on the engine? Let us know in the comments!