Titanium spars and composites on F-22

On Thu, 04 Dec 2003 00:59:57 -0800, Hobo wrote:



I've read that the vertical tail buffeting problem on the F-22 prototype
was solved by replacing composites with titanium spars. This makes me
wonder why the titanium wasn't used in the first place. Was it
cost/weight/stealth or something else?


The same thing happened with the wing spars. They were all composite
and apparently when they did the live fire tests on a fuel filled wing
the composite spars got obliterated (did not degrade "gracefully" :-)
) So now every thrid spar is made of titanium. They didn't do this
from the start because of weight. I imagine a machined titanium rib
probably costs more than a composite one. Stealth had nothing to do
with it as the spars are inside the wing.