Originally Posted by
airsupport
...
Later when with an identical Aircraft based in NY, and operating identical routes to the AA Aircraft, was when we had all the maintenance problems with the composite tail, not in Australia.
I do not know about the possibility of a tail coming off a B747, B737 or any other Airbus, and would never comment on such, however no matter how much you all ridicule me, I do KNOW that with an identical Aircraft (A300-600), operating out of the same Airport (JFK) and operating the same routes (down through the Caribbean), we had lots of maintenance problems with the tail, and I honestly feel this is a hell of a coincidence IF as you all say, this could not have possibly played a part in it.
OK, if I can add my 2cents / 2 ps:
Airsupport, it seems that your case is a subcase of the general potential problem and that is flying outside of design envelope.
Both ground and flight test are there to prove that design is within the required cert requirements. If for any reason these loads are exceeded (either by pilot input or by other means
i.e. engine malfunction, weather etc) structure may (and probably will) fail.
In some fortunate cases when OEM designed structure based on conceptual loads which after the test turn to be far too big (one would think of some older aircraft, like most of the 747 structure) these exceeding loads can be sustained but I think that in that case pilots are required to report overloading.
Only case I know of in which structure is submitted to deliberate failure is the wing breaking after the ground tests are completed. Even in that case, from my experience, several times before the test few tries are made in order to predict the exact load at which the wing will break. This looks good when the real breaking is performed in front of selected guests. A good show off and a huge amount of useful data as well.
Sad occasion when an aircraft fails in flight test (few of Bombardier's examples come to mind, right MFS?) is a good proof of a statement about necessity of staying within the loads envelope.
IMHO one's experience with a specific model in a specific situation (A300-600 flying from JFK to Caribbean) is necessary for a conclusion but not sufficient, to borrow the expression. I can stand behind this statement from the certification standpoint (OEM side, Stress/Structure in particular).
Originally Posted by
AirRabbit
... But no matter what the proper answers are for these concerns, I have yet to understand why anyone would think that maximum control deflection, and repeated reversals, in all three axes, at the same time, was anything close to expected professional aviation behavior - below, at, or above design maneuvering speed.
AirRabbit, you're right on. From the standpoint of what are the loads for which we design, and in my case analyze, the structure - no combination of loadcases is used
i.e. when you design you use a set of SEPARATE loadcases for which you performthe analysis.
There are NO COMBINATIONS, otherwise you will have a hell of a certification task. Quite impossible even if you try. I've seen that tried only once long time ago, and in an environment that was not exposed to cert requirements used in civilian/commercial use (military project). Namely, someone thought of running two loadcases for the structure simultaneously and guess what happened? Total failure and consequent postponement of a project for several months.
You always assume a discreet set of load cases, defined on requirements from relvant FAR/JAR or other document required by local CAA. So, applying simultaneous maneuvers in this case or simultaneous loadcases, in general, is not acceptable.
I fully agree that under circumstances any structure would behave the same as the one on A300-600. You are maybe right when you pinpoint the characteristics of A300 fin design (I am not familiar with it appart from what was published based on this accident) but I do not think this was decisive.
In fact, just to support that statement I know of at least one case of analysis done for new or modified structure bearing in mind this specific accident. Result was failure. By the way, it was a metallic structure, in use for several years.
Cheers