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 expeirence buidling 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


Of course one other possibility is the fact that the aircraft flew, either
by chance or choice (fuel savings) through a thunderstorm and was ripped
apart  by the severe up and down drafts contained therein. There are few
aircraft that  are designed to withstand the stresses imposed by a thunderstorm.
You don't  avoid them just for a comfortable ride. You might be safe doing
that 100 times,  but every once in while you get caught.

I was told by a UAL captain that there is an additional problem trying to
penetrate an area of storms in that area of the world. He claims that the
water  droplets in the thunderclouds due to many factors, are so small that
they don't  paint well on radar. So it is possible to fly through an innocuous
cloud  formation right into a CB.

For those of you that are familiar with airbus and Boeing and aircraft of
that persuasion, What G forces are they designed to withstand???

Some time ago I heard, without confirmation, that the numbers are less than
what we consider normal for our small stuff.

Rich