Different kind of flaw tolerance -- this is the structues/dynamics
margin to take damage and keep flying. It could be big stuff like a
real hard landing or ballistic damage, or small screwups like a guy
dropping a toolbox on a composite fairing. The point is cracks don't
propagate, and you keep flying. It's a complicated thing with new
design, test, and qualification tools that weren't available before.
Sikorsky first civil certified that for the S-92 in 2002, and it has
big payoffs for military applications -- Of course the Navy decided to
pass on the Presidential competiton, but that's their insanity.

Yep, 64B was the notional multi-stage improvement program considered
before the C/D evolution that became the D to save money on manuals --
yes, I go back that far. My point was the 530F gave Boeing the
opportunity to design, fabricate, and certify/qualify a composite blade
while the Army thought about it, and thought about it. You don't just
go and do stuff like that, and that's why multiple civil/military
programs give you opportunities to develop dual-use technologies.

The same with the Bell 430 four-bladed composite yoke that started out
as the 630 rotor (I don't know where they got the designation from).
They knew the obvious application was the Marine Cobra, but it took a
decade for the Marines to do it. Meanwhile the 430 put the thing into
production and got it certified.

Bell claimed over 80 orders in 18 countries for the 609 in 2003. How
many they lost during the testing pause while they ran out of money I
don't know. They just did a helo-airplane conversion on a ground rig,
and they're supposed to do an in-flight coversion by the end of the
year. They ran out of bucks, let the thing sit, and recruited Agusta
as a partner -- that's the rotorcraft opportunity Boeing missed.

Good holiday, folks

HW