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| There are those from outside the aircraft industry like Vern Raburn (Eclipse) and Rick Adam (Adam Aircraft) and even Honda, who think they can beat everyone else by using new technology. |
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| In Vern's case, he believes the friction stir welding process can provide a big advantage over traditional (and proven) riveting methods for joining aircraft parts. Like Cessna is not doing FSW because they have never heard of the process. |
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| It might surprise Vern to learn Cessna has a large staff of manufacturing R&D engineers who have looked at FSW, tested FSW and continue to evaluate FSW today. |
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| While Boeing Huntington Beach is using the process successfully for welding thick skins (.150 to one inch) in rocket applications (as in stay glued together for one flight with no passengers on board), Cessna has found the process to be very sensitive on welding thinner structure (.040 to .063) that is more typical for general aviation aircraft. Even more serious, there is a post-weld corrosion problem that Cessna has not been able to solve and they have tried nearly every trick. |
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The July 2003 issue of Forming and Fabrication had an article on Friction Stir Welding which was basically a Q & A session with John J. Tracy, PhD, VP Structural Technologies and Raj Talwas, Manager-Unitized Metallic Processes; both with Boeing St. Louis (formerly McDonnell Douglas).
Here are a couple of excerpts:
F&F: Is this effort (reducing costs) progressing smoothly?
Raj: There are still many technical concerns. We are interested in friction stir welding commercial fuselages, wing structures, and wing torque boxes. We want to do that in the next two or three years. We are moving slowly, one thing at a time. There are still a lot of technical hurdles to overcome.
John: One of the two main technical concerns is the tooling required. Because this method applies a downward force, unless the geometry is just right, providing proper backup and clamping to the tooling can be difficult. Backup tooling resists the force of the upper tool. For complex shapes, which is really where we want to go, backup tooling is difficult.
F&F: What's the other issue?
John: The other significant issue in commercial aircraft is corrosion. There is concern about corrosion in certain types of joints that needs to be worked through.
Raj: When we friction stir join two plates, the tool comes in from above. Sometimes it leaves a defect on the under-side, called a root defect. The defect is so tight, we can't see it with ultrasonic, x-ray, or even dye penetrant inspections. It's not a big concern on a rocket that has a very short lifetime. But it's a big concern in commercial aircraft.
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| Honda has both launched a design with a composite fuselage and plans to use 6013 aluminum alloy for the empennage in their new small jet. The advantage of 6013? It is easily formed and does not require heat treat. Cessna looked at this alloy six ways to Sunday and concluded it should only be used in very limited applications since it is prone to cracking in certain formed conditions. |
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| Cessna is the world's leading producer of general aviation aircraft. They lead for a reason...they know what they are doing. |
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| Guys, guys, guys!!! It is pretty simple. If Cessna is not using the technology, there is probably a pretty good reason why. |
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