From: dmhills{at}attglobal.net (Don Hills)

In article , "Frank Haber"
 wrote:
>Which prompts me to ask...
>
>Since our wigwag-tail_off A300 accident in Queens, I've wondered, with no
>background in the field at all, whether Airbus has a history of cutting it
>close on stress margins.

You'll find similar stress margins on any modern airframe. You can't afford
to build a heavier plane than your competitors. Modern computing power
makes it possible to more accurately design parts that are just strong
enough.

>Years ago, Boeing had a reputation of building 'em
>stronger, and the perception was reinforced by the Hawaii 737 fatigue-related
>peelback incident.

Design was much more slide-rule in those days, they had to build them
stronger to be sure of building in enough margin. Sometimes they guessed
wrong. If the 737 had the benefit of modern design, it wouldn't have lost
its roof in the first place.

>My pilot friends used to hate the A300's fly-by-wire for
>restricting their options in crisis situations, instead imposing preprogrammed
>sets of actions.  Yet this is directly antithetical to an A300's letting that
>copilot slam his rudder back and forth in a resonant fashion.

To use the classic example of the airshow crash, not having FBW would not
have saved the plane. It's simple energy management. The pilot approached
too slowly and at too low a power setting. If he could have slammed the
throttles open, the engines would have compressor stalled - crash. If he
could have pulled back harder on the stick, the plane would have stalled -
crash. The FBW parameters aren't set conservatively- they're set to the
optimums. In the A300 for example, lifting the nose past the angle allowed
by the FBW would have actually increased the sink rate and the plane would
have crashed short of the point that it did.

--
Don Hills    (dmhills at attglobaldotnet)     Wellington, New Zealand
It's ironic that people who are too smart to engage in politics are
governed by people who are not as smart.

--- BBBS/NT v4.01 Flag-5