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Time to X-plane

Industries on both sides of the Atlantic want greater opportunity to test their technological mettle with flight demonstrators

After the Wright Flyer, one of the most famous aircraft of the first 100 years of powered flight was the Bell X-1. In October 1947, almost 44 years after the Wright brother's first flight, the rocket-powered X-1 broke the sound barrier and launched a line of US experimental aircraft that has done more than any other single series to advance the art of aerospace.

Later this year, the X-50 is scheduled to take to the air. This unmanned vehicle will demonstrate a unique canard rotor/wing concept that combines the hover capability of a helicopter with the cruise speed of a fixed-wing aircraft. A vehicle more different to the Wright Flyer or the X-1 is hard to imagine. And that is the point.

Not all X-planes have been as impressive or as successful as the X-1, or its hypersonic successor the X-15 - still the world's fastest aircraft 35 years on. But each successive X-vehicle's success or failure has contributed to the advancement of technology, testing wings of every shape - swept, variable-geometry and forward-swept - and vehicles of every type - lifting-body, waverider, tailsitter, and tailless.

There has been a flurry of new flight demonstrators in recent years. More than 15 X-vehicle programmes have been initiated in the past decade and, although the mortality rate has been high - at least five have succumbed to technical or financial problems - the US industry wants more.

Boeing's George Muellner, until recently head of the US giant's Phantom Works technology incubator, says flight demonstrators are essential if the industry is to attract talented graduates, develop the skills of its designers and retain the services of its most experienced engineers. The presidential commission examining the health of the US aerospace industry, when it reports later this year, is likely to recommend that the government fund more X-programmes.

There has been criticism of the trend towards using subscale unmanned vehicles, rather than full-scale manned aircraft, to flight test new technologies. Certainly it has been a long time since an X-plane has made a household name of its pilot, like the X-1's Chuck Yeager and the X-15's Scott Crossfield.

But Muellner, for one, believes the X-plane's role is changing - from being a testbed for a single breakthrough to a platform for several complementary technologies. The integration task is no less challenging when the vehicle is unmanned, but it is less expensive.

Europe does not have the USA's long-established experimental aircraft culture, but that may finally be changing. Purpose-designed technology demonstrators like the UK's British Aerospace EAP and France's Dassault Rafale A of the mid-1980s are few and far between. Both aircraft contributed greatly to the latest generation of European fighters, but they were expensive one-offs.

Since the EAP and Rafale A, except perhaps for Dassault's Petit Duc and Saab's Sharc subscale unmanned combat air vehicle flight demonstrators, Europe's advanced design engineers have had to hone their skills in the virtual world of the computer, augmented by all-too-brief windtunnel and test rig campaigns. The opportunity to flight test technology on a modified "hack" aircraft is the most they can hope for.

Two programmes could change that, if Europe grasps the challenge: the European Technology Acquisition Programme (ETAP) and the Future Launcher Preparatory Programme (FLPP). ETAP unites the six European fighter-manufacturing nations in an effort to develop technologies for the next generation of combat aircraft, manned and unmanned. FLPP is a European Space Agency effort to develop technology for a next- generation reusable launch vehicle (RLV).

FLPP will bring together RLV "X-vehicles" already planned in Europe, including France's Pre-X re-entry testbed and Germany's Phoenix approach and landing demonstrator. The g2 billion programme could include larger demonstrators. ETAP involves France, Germany, Italy, Spain, Sweden and UK. The first projects in the long-term programme get under way this year, looking at wideband datalinks, high-speed processing and UAV control. Although none involve purpose-built flight demonstrators, ETAP is the best available framework for Europe to build X-vehicles.

As aerospace companies on both sides of the Atlantic struggle with similar technical and financial challenges, the role of experimental aircraft and other flight demonstrators in building and sustaining a healthy technology base is ignored at the industry's peril.

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