Originally Posted by
jetblaster
Composites are here to stay, no doubt.
But, in answer to Daniel's question, and to comment on Bravo64: Airbus still contends that exterior visual inspection methods with the naked eye, coupled with the old "coin tap test" is adequate to find hidden damage, fatigue or delam in both monolithic carbon fiber composite construction (like the A300 tail lugs) or the honeycomb nomex matrix composite used in rudders and elevators.
Look closely at the wing failure numbers on the A380--they weren't building the airplane to pass the minimal ultimate load threshold by a good margin...they were trying to hit it exactly. This is a change in philosophy--ultimate load was never supposed to be "the target"...
...but cutting corners is what Airbus is all about and there are at least 265 fatalities in a smoking hole in Long Island that show what happens when you cut corners to get an edge on Boeing. As for design, look at the tail of the 777--it is composite, but it is constructed much differently than the A300/A320/A330/A340 tails, with dozens of attachment points that avoid metal-to-composite stress/friction points and there are titanium piers that insure that, if the vertical fin does break off, at least a stub will be left.
That's why, Daniel...Boeing does it better, safer and stronger--they recognize the FAA/JAA certification "standards" to be the "sub-standards" they really are.
Bravo64--do you have a link for the re-certification of the tail? They "beefed" it up, did they? Did they re-certify it with another test, or just "call it good."
(I have much less confidence in the FAA than you do...just look at the 737 rudder issue for a glimpse at their track record.)
Jetblaster
I don't have a link for recertification of the tail - I was referring to the wing ultimate load test. I've been told by some structures engineers at a A380 customer airline that Airbus made some changes to the wing and the EASA bought it off through a paper analysis so Airbus didn't have to break another wing. My guess is that they were close enough so that relatively minor changes (i.e. thicker wing skins and/or beefed up spars) fixed the problem. I'm just curious about what they plan to do to the airplanes that were built before the changes were incorporated. And just about any improvements that make will add more weight to an already obese airplane.
Complying with the 1.5 ultimate load requirement can be a two-edged sword. Since the 1.5 number is a certification requirement, falling short is not an option. Exceeding the requirement, which most pilots may regard as a good thing, usually means more weight which means more money. It gets to be a matter of how far the manufacturer and the airline wants to go.
And if it will make any of you feel better the technology of testing composites have moved far beyond the old quarter tap test. There are a lot of new testing techniques out there (digital radiography, shearography, microwaves, and thermography for example) that do an excellent job of detecting potential problems. This is a big improvement over aluminum where the first indication of a problem is often either a crack or corrosion.