787 flawed

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.