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Lasers drill efficient holey wings

17 Jun 2002

Laser-drilled holes in aircraft wings could make planes fly further on less fuel.

By drilling millions of tiny holes in the leading edge of an aircraft wing, a team of UK-based scientists from Heriot-Watt University and BAE Systems hope to develop a more efficient way of flying. The holes alter the air flow characteristics over the wing and reduce the drag felt by the aircraft.

Results from a preliminary trial on an Airbus perforated fin made of titanium are being assessed. Duncan Hand, a member of the researcher team from Heriot-Watt University, said: "The net gain in reduced fuel or increased ranges is expected to be about 5 - 7%."

Conventional drilling techniques are insufficiently accurate and too slow to produce the number of holes at the size required. The researchers have investigated what sort of laser pulse is best, how much energy is needed and what the most appropriate conditions are in order to optimise their laser drilling process.

The researchers are using nanosecond pulsed, Q-switched Nd:YAG lasers to drill typically 4 million holes per square meter. The energy per pulse is approximately 200 mJ. Holes are drilled at a rate of 50 holes per second but by splitting the laser beam, the researchers hope to increase this to about 500 holes per second in the future.

The diameter of each hole is in the range 30 - 80 µm and on average is 60 µm. The depth of each hole varies from 0.9 to 1.5 mm, although a depth of 1 mm is typically achieved. These variations are facets of the laser drilling process.

"There is an upper limit on hole size as you have to avoid having too high a flow velocity through any particular hole. You want the smallest hole size possible for highest suction uniformity. This is traded off against the uniformity of the hole sizes and the time required to drill the large number of holes," explained Hand.

BAE Systems now plans to apply the results gained to achieve a better understanding of drilled panels and the way in which the laser drilling process affects the performance of the panels. They will combine this knowledge with the results of their hole geometry studies to produce large scale drilled panels with improved performance.

Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe.

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