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Getting under the skin of Clean Sky – with HYPERDRILL

Airliners of the future could benefit from fuel savings of up to 10% by using Hybrid Laminar Flow Control, also known as ’hybrid laminarity’, a technique whereby part of the turbulent airflow around an aircraft is sucked through microperforations in its skin, creating a more stable aerodynamic flow. Clean Sky’s HYPERDRILL project is evolving the unique and ultraefficient production process for the manufacture of these skins, contributing to significant environmental benefits for European aviation.

Drilling over 300 holes per second through titanium sheets sounds like the stuff of science fiction, but that’s the ambition of the HYPERDRILL consortium, coordinated by IK4-TEKNIKER in the city of Eibar, Spain, and supported by BIAS (Bremer Institut für Angewandte Strahltechnik GmbH) of Bremen, Germany. The 36 month project (2017-2020) is one of a number of ’contributing projects’ in the Clean Sky portfolio, which focus around highly specific technical challenges that must be overcome in order to facilitate larger scale projects. In this case, HYPERDRILL contributes towards Demo 1 of the Hybrid Laminar Flow Control (HLFC) Large Scale Demonstrator, part of Clean Sky 2’s Large Passenger Aircraft IADP.

On the HYPERDRILL project’s checklist is the design, manufacture, assembly and testing of a High Throughput laser Micro-drilling (HTMD) prototype machine with process monitoring and quality control for micro-perforating large titanium sheets with a throughput of over 300 holes per second, to be tested within an industrial environment. The objective is that the machine will be able to generate millions of holes, of less than 100 μm in diameter, on titanium panels up to 5 m x 2 m.

“Hybrid laminarity uses a system which sucks the air from the upper parts of the wing through micro holes in the aircraft skin. The purpose of the HYPERDRILL project is to define the machining tools to enable manufacture of the titanium sheets that will be located on the leading edge of the horizontal tailplane for integration for the full system and device, and this project is very specific to this laminar flow application“ says Sebastien Dubois, Clean Sky’s Project Officer for Large Passenger Aircraft.

The technology, at demonstrator level, will be applied to the tail of the aircraft, but the full potential of the system will ultimately be realised when it is eventually installed in the aircraft wings. “In Clean Sky 2 we are defining and maturing the technologies into an industrial context and HYPERDRILL contends with the preparation of the manufacturing techniques to demonstrate the feasibility in actual conditions“, adds Dubois.

By sucking the layer of turbulent air on the surface of the aircraft through the microperforated skin, the air flow around the aircraft can be more predictably managed, creating a laminar flow which reduces drag and therefore leads to savings in fuel and lower emissions. But developing and perfecting the industrial process to produce the perforated sheets with the necessary precision, uniformity, and in a timely manner, is no easy task.

“Laminar Flow Control research began in the 1930s and became important in the 1970s, however first test flights using HLFC techniques on a passenger aircraft didn’t take place until the 1990s. Even now it has been very difficult to find the right technology to carry out the manufacture of an HLFC suction chamber integrated into the wing“ says Carlos Soriano Reyes of Tekniker’s Advanced Manufacturing Technologies Unit, adding that “the design and manufacture of each part of such a device’s structure involves major technological challenges, one of which is the ability to micro-perforate millions of identical tiny holes at high speed on a large metal sheet. The machine is an excellent test bench for the aeronautical sector to evaluate the effectiveness of the system“.

In terms of measurable results achieved to date the design of the machine has been completed and the components are currently being prepared for assembly. It is expected that the assembly will be completed, and the setting up will begin in the middle of 2019. At the end of the project there is a validation task lasting seven months where different large titanium panels will be microperforated and delivered to the aeronautical industry for testing.

As for the environmental benefits, Carlos Soriano Reyes says that “Hybrid laminar flow control technology can result in a reduction of up to 10% in the fuel consumption of civil transport aircraft, which in turn represents a significant environmental improvement through the reduction of CO2 emissions and other pollutant agents into the atmosphere. The improvement, in turn, brings with it the possibility of increasing the level of aircraft payload“.