PPRuNe Forums - View Single Post - Fired engineer calls 787's plastic fuselage unsafe
Old 19th Sep 2007, 21:51
  #42 (permalink)  
Sunfish
 
Join Date: Aug 2004
Location: Melbourne, Australia
Posts: 7,885
ARINC:

Every single frame on the A380 Main deck (98 of them) is Carbon fibre. and in the interests of accuracy they are manufactured completely differently and with far higher tolerances than boat masts ! (I had to laugh at that one) Furthermore only Titanium fixings are used to secure other structural items to them.
As a former professional engineer, and having worked in the aerospace industry, and in an airline, and having visited both Boeing composite manufacturing facilities and mast and hull builders, you are simply wrong to sneer about the manufacturing technology employed and the tolerance achieved. Furthermore the car industry uses about ten times smaller tolerances on their manufacturing processes and use far more sophisticated processes than do airframe builders, but in any case thats not the issue.

The issue is as Weldon succinctly puts it, the very low amount of linear strain before the composite material fails. In other words, it's main failure mode is a brittle fracture. My observation is that the considerable number of carbon hull and mast failures I've seen are consistent with this failure mode, and as a result, are "spectacular" compared to the failure of, say, an Aluminium structure.

What Weldon is alleging is that Boeing has avoided subjecting the 787 fuselage structure to a type of test (A drop test from 14 ft. producing a 30 ft/sec) velocity that in an Aluminium structure produced a maximum 20g deceleration - which is regarded as the maximum for passenger survivability.

The implication of what he is alleging is that the B787 fuselage is not going to behave as well as an Aluminum fuselage in a "Phuket" or "Yogyakarta" type of accident - and the behaviour is going to be worse, not better, with higher G loads on the Pax followed perhaps by the shattering of the fuselage, and possibly the ejection of the contents.

Whether this is likely to happen and whether this is a good or bad thing is beyond my competence. I will be interested to hear Boeing and the FAA's response.

The one thing we can all count on is that whether Boeing wishes to simulate such a situation or not, the B787 crash worthiness is going to be tested by nature, and as Feyneman famously said, nature will not be fooled.

As for his comments regarding Boeing's conservatism and "soul", I can testify that the Boeing I had dealings with twenty-five years ago certainly evinced the qualities of integrity and ethics he talks about, and it would be sad if that ethic has gone. I'm still not sure for example, if the aviation industry is using lithium/aluminium, and high strength low creep magnesium alloys, despite these having been around and tested for forty years.

To sum it up, if the allegations are correct, then this is the same sort of **** that got Douglas into trouble.
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