Which helicopter type was it?

"Stuart & Kathryn Fields" wrote in message
.. .
aluminum control tube failed causing helicopter crash. The helo had an
anodized aluminum control tube that failed in fatigue with less than
400hrs. The loading was low producing stresses in the area of 460psi.
Discussions with anodizing folks say "Never anodize flight critical
components" Some research has provided data indicating that some
cleaners can also shorten the fatigue life of aluminum significantly.
I've seen gyrocopters with long anodized aluminum control tubes shaking
like your English teacher's No-No finger. The May 07 issue of
Experimental Helo has a more indepth article on this with pictures of the
helo before and after..
.