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Aviation glossary

Bypass Ratio

What is bypass ratio?

Illustration related to bypass ratio
Image: FAA Aviation Maintenance Technician Handbook - Powerplant (FAA-H-8083-32), Figure 1-43 — public domain

Bypass ratio is the comparison between how much air flows around the outside of a turbofan engine's core versus how much flows through it. A higher bypass ratio means more air is bypassed around the core, which is typical of efficient, quieter modern jet engines.

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