Why Did Boeing Ditch Its Signature Feature?
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Why Did Boeing Ditch Its Signature Feature?
- Chevrons' Function and Benefits:
- Noise Reduction: Chevrons reduce engine noise by creating small vortices that encourage gradual mixing of different air streams (69% smaller noise footprint for the Dreamliner).
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Economic Savings: Reduced need for sound dampening insulation, saving about 600 pounds on the Dash 8 and similar amounts on other models.
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Chevrons' Drawbacks:
- Aerodynamic Drag: Reduce thrust output by a quarter of a percent during takeoff and climb.
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Manufacturing Complexity: Require precise cutting to generate exact vortices, potentially leading to more rejected parts.
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777X's Noise Reduction Strategies:
- Larger Fan: Uses the GE9X with a fan size of 134 inches and 10 to 1 bypass ratio for better efficiency.
- Efficient Wings: Larger wing span (235 feet) reduces engine thrust needs, lowering noise levels.
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Advanced Nozzle Design: New design planned that will reduce noise as effectively as chevrons but without visible changes.
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Chevron's Future:
- Persistence on Older Models: Chevrons remain standard on the 787 and 737 MAX, with many orders outstanding.
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Long-Term Presence: Given existing designs, Boeing is unlikely to remove them from these programs.
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Boeing’s Decision:
- Cost-Benefit Analysis: The benefits of chevrons are most impactful during takeoff and climb but less relevant at cruise; new technologies offer similar noise reduction without visible changes.
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Market Impact: Lack of a clear visual feature for marketing purposes, making the new nozzle design more appealing.
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Personal Experience:
- Perceived Quietness: The author believes the 777X is even quieter than the Dreamliner despite being larger and lacking chevrons.
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