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Friction-Stir Welding

Eclipse Aviation claims its Eclipse 500 Microjet can be assembled in nine days.

October 2, 2007  By David Godfrey

171The year 2002 was one of triumph mixed with setback for Eclipse
Aviation, the fledging Albuquerque-based airplane manufacturer that may
redefine the future of business travel with a twinjet affordable enough
to spur a national network of air taxis.

The vehicle designed to support this grand vision, the Eclipse 500 flew
for the first time last August. But plans to power the Eclipse with the
lightweight, heavy thrust Williams International EJ22 engine were a
bust. The aircraft maker terminated its relationship with the engine
maker and has since selected the Pratt & Whitney Canada PW610F.

The setback has delayed production by at least 18-months and will
increase operating costs, if not the final price tag of US$850,000. But
while this has fueled critics skepticism, it appears to have not
dampened the enthusiasm of early customers. And while recent focus has
been around the engine, it is the success of less labour intense
production techniques such as friction-stir welding that will determine
the viability of the aircraft.

Friction stir-welding looks like
a leap ahead for aluminum fabrication and is a serious competitor for
all-composite and carbon-fibre construction as a successor to
conventional riveted and adhesively bonded aluminum. Carbon is very
costly and not easy to use, as Raytheon has found out with more than a
two-year delay in certification of the Premier bizjet that has a
carbon-fibre fuselage with conventional aluminum-alloy wings. [The
Eclipse is a sixseater, like the Premier]. Other composites have their
limitations for primary structure, although GLARE (GLAssfibre
REinforced aluminum) is promising.


Friction stir-welding is
being used to join thin aluminum-alloy panels together without
fasteners for the Eclipse 500 cabin, aft fuselage, wings and engine
mounts. The process eliminates rivets while providing joints that are
superior in both strength and weight. It is also a much faster process
than conventional methods of assembly.


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