I read the de lamination article with high interest. As many engineers I
was trying to find a logic in all the information I got about the crash.
I wonder if the de lamination theory of the tail rudders stands firm.
Look at photo below showing it still has a big part of the rudder. It
still looks quite complete.


I found interesting reading on Airbus crashes on
http://www.fear-of-flying.us/index.php?p=1_11_The-Robot-Plane
And more on how the plane possibly broke up in the last lines of
http://www.fear-of-flying.us/index.php?news&nid=8
So the tail probably was torn off at crash?

Randolph in Paris

Randolf sent a picture and I forgot to attach it. Here it is.

Here too are some pictures of the loss of the vertical fin
on the AA-587 flight Airbus crash on Long Island.

Paul Lamar


Dear Paul:

Here is some verrry preliminary evidence on delamination
of the composite tail.  I hope it helps.

Les Nordman


FW: Air France Flight 447þ

From:
Nordman, Paul S

Sent:
Mon 6/29/09 11:48 AM

To: Les Nordman

1 attachment

A340-600_...jpg (559.2 KB)

Les

This picture plus the photo from AW&ST show that the graphite
tail did not break on the air france airplane. Rather the
fin ripped the fuselage frames out of the body when it
came off. However I don't think either of these things
were the cause of the crash. I think the landslide of
events had already started and the airplane was so out
of control that by the time the vertical fin failed,
there was no saving it anyway.


Paul Nordman
Advanced Structures Technology
Boeing



Never the less the fin was found floating 30 miles away.

Sounds to me they are underestimating the loads on
the vertical tail. They may have beefed up the tail after the
original design was done but not the part of the fuselage the
vertical tail was attached to. Very typical of after the fact
structural development. If you beef up a part as an after thought the
next part in the load path fails. A properly designed aircraft
will come apart all at once in random ways. Another possibility
is the tail was over designed due to the uncertainty of it its
composite structure. Perhaps this tail had no cracks that allowed
water to infiltrate, freeze and cause de lamination.

There is a committee at the aircraft companies called the "Aircraft
Load Calculation Group" that decides the loads the aircraft will be
subjected too. This stems from aerodynamic calculations as well as
years of experience building aircraft.

It would be interesting to see what Air Bus uses for loads.
This chart is from the bible of aircraft design "Analysis and Design
of Flight Vehicle Structures" by E.F. Bruhn et al.

However probably the easiest way to destroy an aerodynamically
clean sub sonic aircraft like an airliner is dive it beyond the dive
limit speed. It does not take much of a dive angle in an airliner.

Paul Lamar

Paul,

Agreed completely.  In composites sometime beefing up one location
creates a stress riser, and decreases the modulus elasticity of the larger
structure.  Sort of why SeaWind  landing gear  can tear off no matter
how many inches of FRP laminations are added behind the attach points.

Doug in Japan