Lufthansa Technik has received approval from the European Union Aviation Safety Agency (EASA) to install its AeroSHARK bionic skin on an Airbus A330-300 Discover airliner so it can fly as efficiently as a shark swims.
Aeronautical engineering is a constant battle against an aircraft's greatest enemy: drag. Though an airliner's aluminum-alloy hull may seem unnaturally smooth to the touch, it is surprisingly rough on a microscopic level. A thin layer of air sticks to the hull as the plane pushes through the atmosphere at 480 knots (552 mph, 890 km/h).
However, there is a tiny gap about a millimeter thick between the surface and this layer of air. Called the viscous sub-layer, it is a chaotic swarm of vortices and generally jumbled air.
The result of this thin layer of turbulence is skin-friction drag. It makes up about 50% of total aerodynamic drag, with a corresponding reduction in performance and flight efficiency. Obviously, if this turbulence could be reduced, efficiency could greatly increase.
That is where sharks come in.
Just as aircraft don't have as smooth a skin as one would like, the same is true of sharks. Their scaly skins are very rough – as anyone who'd had the bad luck to be scraped by a shark can tell you. The thing is, these tiny, toothlike scales are what ichthyologists call dermal denticles. That is, they are toothlike scales that have microscopic, raised, parallel ridges.
Running along the length of the shark's body, these denticles do something rather clever. As the water flows over the shark, micro-vortices form, just as they do on an aircraft's skin. In the shark's case, the ridges hold the vortices away from the skin. This suppresses the turbulence, so the shark can swim quickly and smoothly.
AeroSHARK achieves a similar effect by emulating nature's design. It's an artificial polymer film with 50-micrometer grooves embossed in it to replicate the geometry, height, and spacing of shark denticle ridges.
Long story short, the company claims a one percent reduction in fuel and emissions per flight, with up to 2% when the skin is also applied to the wings and empennage.
The EASA approval doesn't mark the first time that AeroSHARK has been installed on commercial aircraft. It's already been tried out on 22 aircraft in Lufthansa Group's own Boeing 777 fleet, where it is reported to have saved up to 19 tonnes of fuel per day.
However, it does mark the point where the technology can now be applied to a whole new family of aircraft, suggesting a greater role for the denticle-inspired surfaces in the future.
"AeroSHARK is an excellent example of how innovations from the Lufthansa Group can make concrete contributions to greater efficiency and lower emissions," said Grazia Vittadini, Chief Technology Officer, Lufthansa Group. "With the planned certification for the Airbus A330ceo, we are tapping into the potential of another significant portion of the global long-haul fleet. The innovation alliance between Lufthansa Technik, Discover Airlines, and Mastercard demonstrates once again how strong partners can drive progress together."
Source: Lufthansa Group
