Nick Orchard from Rolls-Royce agrees that the key to increased fuel efficiency could be as simple as more accurate engine components. Speaking at the National Physical Laboratory's recent Dimensional Metrology Awareness Club (DMAC) meeting, Orchard highlighted that airlines could save up to 1000 litres of fuel on a flight to New York if only they could get their measurements right.

To gain maximum efficiency, manufacturers need to achieve an ideal leading-edge shape for compressor blades. This involves taking precise measurements of shape and surface texture and then manufacturing a number of blades with repeated accuracy. Today, this manufacture and measurement is often undertaken manually and is subject to human error. An automated system, using computer interpretation would reduce error and increase accuracy. This would lead to blades designed with exactly the right measurements to make them perfect time and again. It would also be able to feed data back into the manufacturing process to ensure this repeatability.

Whilst the need is clear, the best way to generate the required data is not and DMAC was the obvious forum to raise the question. The resulting debate at the DMAC annual event was rife as Orchard presented the challenge - how do we accurately measure blade leading-edges for jet engines? Whilst projectors and coordinate measuring machines were quickly rejected due to high potential for error or slow speed, the problems associated with using more advanced techniques including confocal laser probes and optical digitisers were also highlighted, offering no single resolution. The answer may lie in a combination of tools and technology, for example utilising the speed of a surface digitiser in conjunction with the accuracy of a confocal device. The problem is that the research community is still to decide.

Orchard remains in search of the answer. "We know how to solve the problem but we just need better tools to do the job. Today we are simply not able to make what we need to as accurately as we want."

www.npl.co.uk/dmac