On Sep 18, 12:35 pm, C J Campbell
wrote:
On 2007-09-18 07:06:06 -0700, WhoGivesAFig? said:

This could be huge

http://seattletimes.nwsource.com/ABP...2003889769.pdf

Hmmm. A retired employee who worked for Boeing for 46 years claims to
know more than the FAA and Boeing about how planes should be crash
tested. He concludes that composites are not as crashworthy as metal,
but does not back his assertions up with any hard data.

His complaint is that composite materials are stronger in some
directions than they are in others, that cracking is less visible, and
that composites are more subject to fire and more vulnerable to
lightning. He points out that g levels in a crash are unlikely to be
uniform all along a composite structure. All of this is true, but he
seems to be alleging some sort of Boeing coverup of these facts. He
discounts actual experience with other composite aircraft, saying that
either they are not airliners subjected to the stress and number of
flights that airliners get, or that the numbers of such composite
aircraft are too few to be statistically significant.

Of course, his report will make great fodder for trial lawyers when the
first 787 crashes, no matter what the actual cause of death of the
passengers is. Weldon seems to be down at the site trying to tell
people how to crash test an airplane even though he no longer works
there. No doubt his experience is valuable, but he cannot possibly be
aware of everything that Boeing is doing to mitigate these problems and
Boeing is certainly not going to give corporate secrets to former
employees.

--
Waddling Eagle
World Famous Flight Instructor


That was an interesting letter. The questions he raise are all valid.
The public (including us) simply assume that the relevant crash
worthiness and fire worthiness results have been thoroughly studied
and found to be adequate. I am assuming that Boeing has the answers to
these questions, but if they don't, this is the time to be asking
these questions.

I have personally witnessed the post-crash fire of an experimental
Velocity. When the fire was out, there was nothing left on the ground
except some metal parts from the wheels, avionics and control links.
All the composite parts had simply evaporated. It was unbelievable.
The two occupant were taken with severe burn, but I never found out
whether they survived.

I also personally know of a pilot who experienced a lightening strike
on his all-composite experimental airplane. There were some burn marks
on the airframe, and all his avionics had to be replaced. Although
there did not appear to be any structural damage, he was saying there
was no way of checking if there are any internal problems due to
delaminations. We assumed that production models probably use an
embedded wire mesh to discharge the current.