Bureaucracy and conservatism in Britain鈥檚 aerospace industry is condemning promising inventions to the scrapheap. An invention as simple as a redesigned screwhead that can be screwed in tighter and is less likely to break while being inserted or removed appears all but doomed through lack of investment. But broken screws cost aerospace companies millions of pounds in maintenance each year. A similar neglected invention is a wire insert to lock the thread of a screw in place.
Both inventions have foundered against a sea of red tape. Individual companies can adopt and use new products such as screws, drawing up their own specifications for them. But the Society of British Aerospace Manufacturers (SBAC) will not draw up industry-wide standards for products 鈥� which would promote wider confidence in their use 鈥� until approached by at least two or three companies.
John Clatworthy, the secretary to a number of technical committees at the SBAC including the one that tests screws, admits that the system sometimes works against inventors. But he points out that aerospace engineers must of necessity exercise caution. 鈥業t鈥檚 the guys in the design offices at companies who say whether or not to use novel devices.鈥�
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John Galbraith, an independent inventor and freelance aircraft engineer based in London, has fought in vain for years to interest the aerospace industry in his patented screwhead design. He cannot afford to have the design thoroughly tested independently, which is only the first step towards acceptance by the industry and the SBAC.
鈥業鈥檝e been round and round in circles since I first approached the Ministry of Defence,鈥� he says. 鈥極ver two years, I was shunted from the MoD to the SBAC, then to British Aerospace then back to the MoD.鈥�
One advantage of Galbraith鈥檚 design over conventional screwheads is that the recess where the screwdriver fits in is less likely to wear away or be damaged. The other is that engineers can make the screws between 30 and 50 per cent tighter than conventional ones. This is because the screws are better able to spread the twisting force 鈥� or torque 鈥� of the screwdriver equally on all surfaces of the prism-shaped recess.
Galbraith says that the screws have most potential in reusable space vehicles, such as the shuttle, which are subject to vast stresses. 鈥楾he tighter screws would increase the integrity of the jointed structure,鈥� he says. 鈥業f you have a loose panel, for example, it will overstress other areas of the fuselage.鈥�
Galbraith points to a report commissioned by the Pentagon in 1976 which found that at that time, screw fastener failures cost the US Navy 拢98 million during the life cycle of a fleet of 187 S3A Viking aircraft.
David Light, a principal engineer at British Aerospace Dynamics in Filton, Bristol, backs Galbraith鈥檚 claims about the merits of his screws. 鈥業 wish I鈥檇 thought of it,鈥� he says.
Light adds with regret that in the present recession, Galbraith simply could not raise the 拢15 000 required for British Aerospace to analyse and test the screw, and then use the computer modelling technique known as finite element analysis to work out the optimum shape for the screws to withstand the expected stresses.
Light鈥檚 team at British Aerospace has evaluated the other device, a wire thread insert which provides an antivibration lock in the tapped hole when torque is applied to the screw. Known as Spiralock and developed by Cross Manufacturing of Bath, Light describes the device as 鈥榚xceptional鈥�.
Despite the glowing testimonies, no aerospace companies have ventured to use the inserts. Nor have any companies approached the SBAC to approve or standardise the product. Rodney Cross, a director of Cross Manufacturing, says that the company just won its first order for the inserts, which are to be used in gearboxes on London Underground鈥檚 trains. But he adds that 鈥榦ur natural customers鈥� in aerospace have yet to show interest, despite having requested and received hundreds of samples from Cross.
Clatworthy sympathises with beleagured inventors. 鈥業f there鈥檚 a good invention, it鈥檚 a shame to see it go out of the country,鈥� he says. But he warns that approving a new technique for use in aerospace is not a trivial process. 鈥業f a screw (on a train) breaks in a tunnel, the train stops in the tunnel. If a screw breaks on an aircraft, it could fall out of the sky.鈥�
