In a bid to achieve net-zero carbon emissions by 2050, flag carrier Japan Airlines (JAL) is undergoing flight trials using two Boeing 737-800s to test the durability of “sharkskin” riblet technology to boost fuel efficiency by reducing friction drag on the airplane's skin. Applied in a specific manner, the exterior riblet coating imitates the skin of sharks and diminishes the effects of skin friction by moving vortices away from the aircraft’s surface. According to JAL, the application of sharkskin riblets can improve fuel savings by 2 percent.
The test campaign is being carried out under a joint research agreement involving JAL, the Japan Aerospace Exploration Agency (JAXA), industrial paint company O-Well, and Nikon Corp. Boeing is also working in cooperation with JAL’s engineering arm to optimize the coating application process.
The trials involve two types of proprietary riblet processing technology—O-Well’s paint and coating method, which uses a water-soluble mold to apply the riblets, and Nikon’s laser microfabricated film process, which can either directly process riblets or attach riblet-processed film, depending on the material surface. Nikon said its laser method can be applied to aircraft bodies and turbine blades. Future plans call for an autonomous control process machine to coat large aircraft surfaces.
“A long-term riblet effect can be expected even in parts with long replacement cycles, as the original durability of the coating can be maintained by direct processing using Nikon's unique laser processing technology,” Nikon said in a statement.
For flight trials, both riblet techniques are being tested separately on the belly of each Boeing narrowbody. According to JAL, the depth of the riblet grooves is 50 microns—about the thickness of a human hair.
“As of now, more than 1,500 flight hours have been accumulated in the O-Well method aircraft, and more than 750 hours in the Nikon method aircraft,” JAL said in a statement. “The riblets applied by both O-Well and Nikon have been confirmed to have sufficient durability.”
JAL’s flight-test campaign includes wind tunnel tests and vortex simulations using a JAXA supercomputer to evaluate the reduction of skin friction. The airline said it aims to reduce CO2 emissions by FY2023, with plans to apply the riblet coating to a number of aircraft in its fleet, including airplanes on international routes, to cut fuel burn. It is among a handful of airlines trialing the application of riblet technology as the industry moves toward lowering its carbon footprint.
In October, All Nippon Airways (ANA) rolled out its Boeing 787 Dreamliner Green Jet program using Nikon’s laser film process. Meanwhile, Lufthansa Technik and multinational chemical company BASF have modified two Boeing 777s—a 777-300ER and a 777F—using its proprietary AeroSHARK surface technology, which lowers fuel consumption and CO2 emissions by around 1 percent. The group received a supplemental type certificate (STC) for the modification from the European Union Aviation Safety Agency (EASA) in December.
AeroSHARK launch customers Swiss International Air Lines and Lufthansa Cargo are now premiering the technology with plans to modify their 777 fleets with the riblet film. Swiss is looking to modify all 12 of its 777-300ERs while Lufthansa Cargo will apply the technology to eleven 777Fs. BASF said the modifications will cut the Lufthansa Group’s carbon emissions by more than 25,000 tonnes annually.