Spiral Zero

Engineers like the phrase \"design spiral\", to refer to a development\nprocess characterised by a series of iterative improvements and additions,\nparticularly where they may be needed to meet evolving requirements. The term\ncomes from software design, and is seen as a dramatic improvement on the linear\ndesign process which usually characterises more traditional manufactured\nproducts.

What makes the spiral attractive is the potential to continuously\nrenew a system so that it always incorporates the latest technologies and meets\nthe latest needs. In a linear design process, specified requirements would be\nfollowed by design, prototyping, testing and manufacturing. Each step is\ncompleted before work flows over to the next stage, and hence the process is\nsometimes referred as the \"waterfall\" design method.

Big aircraft programmes which begin with a request for\nproposals that lead to carefully detailed performance specifications are good\nexamples of the waterfall approach. Given the enormous investment in tooling\nand materials required to make such a complex physical (as opposed to software)\nsystem, this linear approach seems unavoidable. However, because it's easy to\nfall off a waterfall but very difficult to go back up, adding new technologies\nor changing components is very expensive once an aircraft is in production.

To cite a specific and very current example, one of the\nfactors contributing to Boeing's travails with its much-delayed 787 airliner\nprogramme is arguably what amounted to an attempt at highly compressed spiral design, by carrying\nout the prototyping, testing and manufacturing phases simultaneously. Looked at\nfrom that perspective, the 787 would illustrate why in popular language the\nword \"spiral\" is so often associated with the phrase \"out of control\".

But the language made a small spiral forward this week at\nthe DSEi defence equipment exhibition in London.\nGianfranco Terrando, senior vice president for unmanned air systems at Finmeccanica's\nSelex Galileo unit, referred to a flight test planned for later this year on a\nGeneral Atomics Predator B of a new open architecture concept in payload\nintegration as \"spiral zero\".

The concept is to create a family of options for packaging\nsensors and data management software so that customers can, ultimately, combine\nany sensors and data handling techniques with whatever airframe they like. A\nspiral development process makes such a concept possible - if each new requirement\ndemanded that engineers go back to stage one and devise a system from scratch,\nthe cost and time involved would, clearly be prohibitive.