Japan Airlines (JAL) is conducting durability tests with “riblet” coatings that can be applied directly over the paint of an aircraft.
JAL’s partners in the project are the Japan Aerospace Exploration Agency (JAXA), O-Well Corporation, and Nikon.
JAL claims that these are the first “sharkskin” riblets that can be applied as coatings directly over an aircraft’s existing paint, and that this saves weight.
Sharkskin riblets are known to reduce friction along an aircraft’s skin by moving tiny vortexes away from the aircraft’s surface.
JAL adds that applying riblets over most of an aircraft’s skin can result in fuel savings of 2%.
The project saw O-Well’s coating applied to a small area on the belly of one JAL 737-800, and Nikon’s to another. The aim of the work is to test the durability of the coatings.
“Durability tests are currently being carried out by performing repeated inspections, measuring the changes in the shapes of the riblets incurred during test flights,” says JAL.
O-Well’s coating uses a water-soluble mould to apply the riblets, while Nikon uses a laser process. The depth of the riblet groves is 50 microns, about the thickness of a human hair.
JAL adds that applying either coating requires a high degree of skill, because they are “very sensitive” to such factors as the type of underlying paint, as well as the temperature and humidity at the time of application.
So far, the 737 with the O-Well application has flown 1,500h, and that with the Nikon application 750h. Both the O-Well and Nikon coatings have demonstrated “sufficient durability.”
“JAL will establish an optimal method on a large area that will reduce CO2 emissions as early as FY2023, and will further improve fuel efficiency by increasing the number of aircraft with riblet coating, especially aircraft for international flights that are more effective in reducing fuel consumption,” says the carrier.