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A Japan Airlines (JAL) Boeing 787-9 with drag-reducing riblet paint over most of the fuselage is expected to enter service on international flights in mid-January.
The operational demonstration is a follow-on to domestic riblet evaluation flights conducted on a 737-800 in 2022 and 2023.
The demonstration is a joint effort between JAL, the Japan Aerospace Exploration Agency and Japanese company O-well, which has developed the large-area paint-to-paint riblet application technology. A drag reduction of 0.24% in cruise is expected on the 787, saving 119 metric tons of fuel a year.
Riblets are microscopic grooves aligned with the airflow that reduce skin-fiction drag by limiting the surface area in contact with airflow over the fuselage. O-well’s process directly applies the riblets to the aircraft paint, reducing weight and improving durability compared with adhesive films, JAL says.
In the process, aircraft paint is applied to a water-soluble riblet mold layer. The coating is then bonded to the existing aircraft paint. The mold layer is flushed away with water, leaving a riblet-shaped coating layer on the aircraft fuselage.
After testing small panels on a 737-800 in July 2022, JAL coated most of the lower fuselage of the aircraft for test flights in November 2023. Further development of the paint-to-paint process has now allowed JAL to expand use to most of the forward fuselage and upper rear fuselage of the 787.
While research and testing of riblets has been under way for decades, confirming the potential drag savings, adoption has been slow. AeroShark, an adhesive riblet film developed by Lufthansa Technik and BASF, has been applied to 777s operated by some Lufthansa Group airlines and EVA Air.