787 flawed

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.

"Andrew Sarangan" wrote:

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.

IOW, about the same as what's left of a burned out aluminum airplane.

The two occupant were taken with severe burn, but I never found out
whether they survived.

And they'd have fared better in an aluminum airplane? Why?


--
Dan
T-182T at BFM

On Sep 18, 10:46 pm, "Dan Luke" wrote:
"Andrew Sarangan" wrote:
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.

IOW, about the same as what's left of a burned out aluminum airplane.

I have only seen photos of metal airplane crashes, and in most cases
you can tell that it was an airplane crash. Many tell tale parts of
the airplane will remain intact. In this case you would not have known
that this was an airplane crash. There were no discernible parts.
Aluminum melts around 650C. Fiberglass epoxy will turn into a gel at
a far lower temperature, around 100C. Most fiberglass airplanes can't
even withstand normal heat from the sun unless they are painted
white. So the fact that the glass airplane simply vaporized in the
fire makes sense to me.

In any case, my observations are only anectodal, and are based on
homebuilt aircraft. Boeing may be using advanced epoxies with superior
thermal and mechanical properties. If that is the case, it would be
trivial for them to put these concerns to rest. I hope that is indeed
the case, and that the 787 is not built with the same epoxy I am using
on my homebuilt.

In any case, my observations are only anectodal, and are based on
homebuilt aircraft. Boeing may be using advanced epoxies with superior
thermal and mechanical properties. If that is the case, it would be
trivial for them to put these concerns to rest. I hope that is indeed
the case, and that the 787 is not built with the same epoxy I am using
on my homebuilt.

Did you lay your composites up on a frame and bake them at high
temperature and pressure in a giant autoclave to cure them? If not,
then I bet you aren't using the same materials or processes...

"Andrew Sarangan" wrote:
Fiberglass epoxy will turn into a gel at
a far lower temperature, around 100C.

It won't withstand boiling water?

On Sep 19, 3:01 pm, Richard Riley wrote:
On Wed, 19 Sep 2007 11:18:58 -0500, "Dan Luke"

wrote:

"Andrew Sarangan" wrote:
Fiberglass epoxy will turn into a gel at
a far lower temperature, around 100C.

It won't withstand boiling water?

The epoxies used in homebuilts - cured at room temperature - generally
start to soften around 200 degrees F. It varies with the epoxy and
with what temperature any one part has been exposed to before - you
can post cure many epoxies by subjecting them to higher temperatures,
and get their transition temps up, by as much as 70 degrees F.

The epoxies used in the 787 are cured at much higher temperatures to
begin with.

But this can't be too difficult for Boeing to explain. All they have
to say is "our fiberglass is treated to handle as much heat as
aluminum" or something similar, if that is indeed true.

On Sep 19, 11:22 pm, Richard Riley wrote:
On Wed, 19 Sep 2007 17:22:59 -0700, Andrew Sarangan


The people that really matter - the FAA - already know.

That assumes that FAA and Boeing are being faithful to their
practices. I am not suggesting that they are not, but there are
reasons to be cautious. We have seen examples in recent times where
that assumption turned out to be false due to company financial
pressures.


If I were the
head of Boeing's PR department, I'd hold off on trying to convince the
public until it's clear whether the story has legs or not.


Even the epoxies used for thing like this aren't as heat resistant as
aluminum - but at some point it doesn't really matter. If the
fuselage is seeing 400 degrees, there's something very seriously
wrong, like the airplane is sitting in a giant pool of burning jet
fuel.

I can agree with that. But there are scenarios where the fuselage does
not have to be soaking in burning jet fuel to see 400C. For example a
service truck could be parked with its exhaust directly aimed at the
fuselage. That may sound too simple and silly, but it was a silly
thing like a foam block that caused catastrophic results for the space
shuttle.



In a situation like that I'm not sure whether aluminum or carbon will
last longer. Aluminum WILL burn, once it gets hot enough, and is very
energetic (think thermite). The carbon fibers themselves can
withstand very high temperatures (think the leading edge of the space
shuttle wing - carbon fibers in a carbon matrix). Epoxy will burn,
but not all that energetically.

As for crashworthyness - I know of three Berkuts that were absolutely
totalled, where the occupants survived. One tumbled down the runway,
one struck a high tension powerline, one deadsticked onto a freeway,
got it's wing torn off by a tree and went head on into an SUV. I saw
the wreck of Bill Davenport's Long EZ - engine out, wires tore off a
wing, went inverted into a garage. He lived. Race cars are all
composite now - and race driver deaths are very rare.

Composite structures CAN be absolutely crashworthy. For the same
weight as an aluminum structure, it can provide much more crash
protection. I don't know how the 787 is being engineered, but I'd be
very surprised if they were deliberately making it LESS crashworthy.
After all - Boeing executives fly on these airplanes too. - Hide quoted text -



I agree that composites have many advantages, and that's why I decided
to build a composite aircraft. However, thermal stability is not one
of their high points.

Andrew Sarangan wrote:
On Sep 19, 11:22 pm, Richard Riley wrote:
On Wed, 19 Sep 2007 17:22:59 -0700, Andrew Sarangan


The people that really matter - the FAA - already know.

The FAA? That's a warm fuzzy. They can't find their ass with
both hands most of the time.

On Sep 20, 11:56 am, Andrew Sarangan wrote:
On Sep 19, 11:22 pm, Richard Riley wrote:

On Wed, 19 Sep 2007 17:22:59 -0700, Andrew Sarangan

The people that really matter - the FAA - already know.

That assumes that FAA and Boeing are being faithful to their
practices. I am not suggesting that they are not, but there are
reasons to be cautious. We have seen examples in recent times where
that assumption turned out to be false due to company financial
pressures.

If I were the
head of Boeing's PR department, I'd hold off on trying to convince the
public until it's clear whether the story has legs or not.

Even the epoxies used for thing like this aren't as heat resistant as
aluminum - but at some point it doesn't really matter. If the
fuselage is seeing 400 degrees, there's something very seriously
wrong, like the airplane is sitting in a giant pool of burning jet
fuel.

I can agree with that. But there are scenarios where the fuselage does
not have to be soaking in burning jet fuel to see 400C. For example a
service truck could be parked with its exhaust directly aimed at the
fuselage. That may sound too simple and silly, but it was a silly
thing like a foam block that caused catastrophic results for the space
shuttle.





In a situation like that I'm not sure whether aluminum or carbon will
last longer. Aluminum WILL burn, once it gets hot enough, and is very
energetic (think thermite). The carbon fibers themselves can
withstand very high temperatures (think the leading edge of the space
shuttle wing - carbon fibers in a carbon matrix). Epoxy will burn,
but not all that energetically.

As for crashworthyness - I know of three Berkuts that were absolutely
totalled, where the occupants survived. One tumbled down the runway,
one struck a high tension powerline, one deadsticked onto a freeway,
got it's wing torn off by a tree and went head on into an SUV. I saw
the wreck of Bill Davenport's Long EZ - engine out, wires tore off a
wing, went inverted into a garage. He lived. Race cars are all
composite now - and race driver deaths are very rare.

Composite structures CAN be absolutely crashworthy. For the same
weight as an aluminum structure, it can provide much more crash
protection. I don't know how the 787 is being engineered, but I'd be
very surprised if they were deliberately making it LESS crashworthy.
After all - Boeing executives fly on these airplanes too. - Hide quoted text -

I agree that composites have many advantages, and that's why I decided
to build a composite aircraft. However, thermal stability is not one
of their high points.

All commercial airports have a fleet of foam cannon fire trucks, don't
worry be happy !