Originally Posted by
jetblaster
Not true, at least, not true according to the latest
NTSB Safety Recommendation and AOT issued by Airbus in response to the Air Transat and Fed Ex tail/rudder disintegrations. They STILL advocate that the visual and coin tap is "good enough"...at least for the A300 and A310. That is what is so shocking...that Airbus can lose essentially four tails in a row on that aircraft type, yet still stand by the coin tap and visual test. (See the NTSB website if you wish to read the entire document, it was the Safety Recommendation that came out in May of 2006 on the Airbus 300/310).
The fact that a knowledgeable person like yourself seems to think otherwise is part of the problem...
**we assume** that the newest technology is being used...but, in fact, **it is not in all cases.** The A300 and A310 is a glaring case.
As far as aluminum goes, the eddy current electrical testing--a form of NDT--was instituted after the Ahola "convertable" room peel back on their 737, found to be corrosion and fatigue.
And, a "paper fix" on the A380 wing is what I was afraid of...and I share your concern on the pre-existing wings. Finally, more weight is part of the safety margin that Boeing has been willing--and is still willing--to "suffer" to make sure their aircraft don't fall apart in midair, like AA 587, AA903, Air Transat 961, etc.
Jetblaster
First of all, I don't think that I stated in my post that I believe that tap tests and visual inspections are "good enough" to determine the structural integrity of composites. If that is what came across, it wan't my intent. The point I was trying to make is that NDT techniques for composites has made significant advances since the early days.
Aircraft maintainers have several different options available to them when it comes to inspecting composites or any other material used on an airplane. Which of these tools is used depends on the situation (i.e. ramp or hangar), the type of material, the type of structure, and the maintenance procedure. There are no silver bullets and no single test is the optimum choice for all situations. While you seem to have a problem with visual inspection, that is probably the most important and most useful method available. After all, isn't that what a walk-around inspection is?
The tap test used to be the primary means of testing composite structure. While there have been several new and more accurate NDT methods (such as I listed earlier) to determine the structural integrity, the tap test is still considered a valid means to discover certain types of of flaws in composites. Often when a component fails a tap test the next step is to follow up with a more comprehensive (and complex) test.
And while you are right about eddy current testing being a way of testing aluminum structure, it is usually only when specifically mandated by either a maintenance task card, AD, service bulletin, or by engineering. Most structural discrepancies are discovered by the old Mk II eyball.