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rgbrock1
7th Oct 2009, 15:46
All,

If you bear with me here you'll see why, I believe, this thread belongs in Tech Log.

I've been doing some research/reading - for knowledge purposes only - about the Boeing 787 Dreamliner which will eventually fly some day.

However, some of what I've been reading/researching has me a bit concerned about a couple of items. Perhaps someone can set me straight on these points.

1. According to the FAA, there is concern in that agency about the aircraft's system vulnerability. Supposedly the system network in the cabin (for use by passengers to access the Internet, amongst other things) is connected to the aircraft's control, navigation and communications system. As a systems engineer by profession I find that quite difficult to comprehend. Yes, this issue is supposedly mitigated by firewalls and separate physical conduits but I still find this difficult to accept. There are many ramifications here, if this is indeed true. Does anyone have any additional info on this?

2. The All-Composite fuselage. Yes, I know modern aviation has pretty good experience with the use of composite materials. But this aircraft would be the first with an all-composite fuselage. My only question/concern here would be the life-span of such a fuselage. Yes, Boeing can test and test and test to their heart's content in order to get this aircraft "air worthy". But what about long-term? One really cannot test for long-term issues such as the effects flight cycles have on such an airframe ie, fatigue. Is this cause for concern? What about maintenance of such a fuselage? How would, for example, cracks be discernible? (I wouldn't think they'd be obvious during a visual inspection?)

I know I've written this rather simplistically but with my lack of knowledge in the technical aspects of aviation, it's the best I could do.

Thank you.

ChristiaanJ
7th Oct 2009, 16:15
1. Supposedly the system network in the cabin (for use by passengers to access the Internet, amongst other things) is connected to the aircraft's control, navigation and communications system.I think (as an ex-systems engineer) that you will find the connection is strictly one-way, such as from e.g the navigation system to the IFE for the in-flight map, or from the comm system to the PA. There is simply no "highway" to send any data in the opposite direction.

2. The All-Composite fuselage. Yes, I know modern aviation has pretty good experience with the use of composite materials. But this aircraft would be the first with an all-composite fuselage. My only question/concern here would be the life-span of such a fuselage. Yes, Boeing can test and test and test to their heart's content in order to get this aircraft "air worthy". But what about long-term? One really cannot test for long-term issues such as the effects flight cycles have on such an airframe ie, fatigue.Life-span would be determined much as with any other modern aircraft: there will be a fatigue test airframe, that is subjected to the same loads as occur during a flight, but that will accumulate "flight cycles" much faster than any aircraft in service.
Concorde was an example of a "new" aircraft, because it was the first civil aircraft where the thermal cycling of the airframe became a significant part of the fatigue testing. The fatigue test specimen went through 20,000 cycles, while in the end the oldest airframes did reach only about 7,000 cycles.
What about maintenance of such a fuselage? How would, for example, cracks be discernible? (I wouldn't think they'd be obvious during a visual inspection?)I think you will find (in other threads here, and elsewhere) that this still is a point of discussion. There are various NDT techniques for composites, but you're right in that a "ding" from maybe a service truck is bound to be less visible than the correponding dent in an aluminium skin panel.

CJ

STBYRUD
7th Oct 2009, 20:03
I agree with Christiaan, contrary to popular belief, at least the media's belief, the 787 systems are, according to Boeing, in no way (except the power supply naturally) connected to the IFE systems, a lot of standards for this exist in the industry, they involve the use of 'air gaps' (the philosophy that systems should be separated to such a degree that they have no interconnection at all AND be physically separated to make electromagnetic interference very unlikely) and various other means to make sure the tech savvy 14 year old in seat 34 E doesn't disconnect the autothrottles from his laptop. About the use of new materials-well. I've heard differing opinions from several people about this, but stress testing nowadays can simulate thousands of landings / pressurizations / flight hours in a couple of months, nevertheless I would like to see how a carbon fibre airplane behaves during a gear up landing - I'm sure Boeing has that figured out though. The Conchorde comparison is quite adequate, after all the Conchorde was supposedly the most thoroughly tested plane before starting commercial ops, and I doubt Boeing will save money by cutting corners in their development process ;)

WindSheer
7th Oct 2009, 23:20
...continuing on the question of composite fatigue etc.

Anyone know if these composites have the same kind of flexibility as their metal counter-parts??
How would they live up to numerous landings in ,say, the asian market??

Cheers.:ok: