What is that sawtooth like pattern on the edge of some aircraft engines?

You might have always been wondering why the leading edges of a Boeing 787 and Boeing 747-8 engines have this sawtooth-like pattern. Are they for aesthetic purposes only?

These are actually called chevrons, and they have a certain purpose why they are there.

The chevron's primary purpose is reduce engine noise or to make jet engines more quiet and is currently used only by Boeing on their GEnx, Rolls Royce Trent 1000, and the CFM LEAP 1B. Aircraft that uses them are the 787, 747-8, and 737 MAX.

As hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces turbulence that creates noise.

According to NASA, "Successes like chevrons are the result of a lot of different, hard-working people and are the result of a lot of very small efforts that all come together, often across many scientific disciplines," said James Bridges, NASA associate principal investigator responsible for coordinating aircraft noise research.

While they may be simplistic in design, Chevrons are a actually a result of years of experimentation using intricate research tools throughout its development.

"Early on, we didn't have the advanced diagnostics, instrumentation and insight to know what we had done to make it worse instead of better," Bridges said. "You have an idea and then you cut out a piece of metal and try it. Sometimes the kernel of the idea might have worked out, but the way you did it wound up causing more noise."

We are unaware if Airbus will also use this same technology on their aircraft but in reality though, their PW1100G-JM on their A321neo are so far the most quiet once we've ever heard. These engines however doesn't make use of chevrons.

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