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777F Floor Beams - Aluminum?  
User currently offlineSandiaman From United States of America, joined Nov 2003, 88 posts, RR: 0
Posted (10 years 2 months 3 weeks 3 hours ago) and read 4581 times:

I heard that a hypothetical 777F would require aluminum floor beams rather than the current composite design.

If true, are composite floor beams inherently unsuitable for freighters? I understand that there are different strength requirements, but one should be able to increase gauges of existing materials to meet the strength requirements.

Also, would the A380F have composite or aluminum floor beams?

13 replies: All unread, jump to last
 
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 1, posted (10 years 2 months 3 weeks 2 hours ago) and read 4520 times:

Composite Floor beams ? have never come across an aircraft with composite floor beams, Boeings and Airbuses use 7075 matl for their beams, boeings with the SRM repairs and airbuses with there complete part change.
if you made floor beams thicker you would have the obvious effects of losses in other areas, fuel load/payload, Composites are a lighter technology but less cost effective, I can see problems with de lamination under galleys being a pain, but then maintenance companys take lots of cash from floor beam corrosion anyway.
Were have you read about composite floor beams ?


User currently offlineLMP737 From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 2 months 3 weeks 1 hour ago) and read 4493 times:

I've heard somewhere that the composite floor beams would have to replaced by aluminum ones. However don't quote me on that because I'm not sure myself. Maybe a 777F would use "beefier" composite floor beams.



User currently offlineAuae From United States of America, joined Apr 2004, 296 posts, RR: 3
Reply 3, posted (10 years 2 months 2 weeks 6 days 10 hours ago) and read 4365 times:

A/c Train,

The 777 uses composite for most of the floor beams. If I remember right I don't think it was the entire beam, maybe just the web. ?? In any case, a diagram I have shows it uses graphite for the floor beams.

I can't see why they would need to change material on the floor beams to make it a frieghter. I think it would actually be a bad thing, as the thermal coeffiecents for graphite and aluminum are different. Those beams are pretty long, I would think you might get undesirable stresses at the fuselage joint.

Shawn



Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
User currently offlineKlaus From Germany, joined Jul 2001, 21479 posts, RR: 54
Reply 4, posted (10 years 2 months 2 weeks 6 days 8 hours ago) and read 4341 times:

As far as I know, the upper level of the A380 has composite floor beams.

User currently offlineSandiaman From United States of America, joined Nov 2003, 88 posts, RR: 0
Reply 5, posted (10 years 2 months 2 weeks 6 days 7 hours ago) and read 4329 times:

True, the thermal coefficients for composites and aluminum are different, but they've obviously dealt with it on the current 777 and A380.

In any case, it ought to be somewhat easier to design an aluminum floor beam that attaches to an aluminum fuselage frame, although the end result might be heavier.

I'm not sure why you couldn't just "beef up" the existing composite beams as LMP737 suggests.


User currently offlineDl757md From United States of America, joined May 2004, 1562 posts, RR: 16
Reply 6, posted (10 years 2 months 2 weeks 6 days 5 hours ago) and read 4300 times:

It's not a strength issue so much as it is an impact resistance issue. Aluminum is superior to carbon composites in impact resistance.


757 Most beautiful airliner in the sky!
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 7, posted (10 years 2 months 2 weeks 5 days 5 hours ago) and read 4167 times:

DL757, I cant think of many situations a floor beam is subject to an 'impact', more cyclic loading on the fact its primary structure, with a structure that must have flexibility in it.
I see the term 'impact' in a sense of a radome taking a bird strike.
It would be interesting to see how critical bonding is when you start using composites more and more as primary structure, I agree that AL has greater impact resistance than composite.


User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 8, posted (10 years 2 months 2 weeks 5 days 4 hours ago) and read 4165 times:

Apologies, I just realised the topic is to do with a freighter a/c, im seing big freight crates being loaded now, but I still believe although ive never taking up flooring on a freighter and worked on the structure, that the flooring must distribute the load significantly to make the 'banging' around of crates negligable.

User currently offlineSandiaman From United States of America, joined Nov 2003, 88 posts, RR: 0
Reply 9, posted (10 years 2 months 2 weeks 4 days 22 hours ago) and read 4125 times:

Finally got a hold of my contact:

In a nutshell, freighters have to be good for concentrated loads, so the floor beams would need to be resized. Because of manufacturability issues, there's a limit to how much the existing 777 composite beams can be reinforced, so aluminum is the preferred choice here.

But it sounds like the issue is specific to the 777, not freighters in general


User currently offlineAuae From United States of America, joined Apr 2004, 296 posts, RR: 3
Reply 10, posted (10 years 2 months 2 weeks 4 days 9 hours ago) and read 4060 times:

Good info Sandiman, I assume the concentrated loads might happen with unpalatized cargo.

Anyone work freighters? I was wondering if all of them had AL-AL core floor panels. Can't imagine them not, but thought I would ask.

Shawn



Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
User currently offlineMiamiair From , joined Dec 1969, posts, RR:
Reply 11, posted (10 years 2 months 2 weeks 4 days 9 hours ago) and read 4060 times:

The key concern with floow beams is not impact resistance. That would be something you would have on a trailing edge flap (which adds layers of Kevlar or fiberglass for this very reason. Floor beams are not stand alone in the floor structure. There are four basic elements: The floor beams, the seat track beams, the floor panels and the actual attachments to the fuselage. The reaction loads from your payload (Cargo or pax in their seats, along with galleys, lavs, class dividers) ultimately react at the interface of the floor beam/fuselage, but the other elements above are designed to distribute the loads.

Composites are more efficient due to their strength to weight ratio. Are composites the answer? Most definitely not. There have been numerous durability issues, but I don't think that would apply to floor beams.

I remember hearing a while back that UAL had problems with the FWD galley area in their 777's and that floor beams were being affected, but I don't know what became of it.



User currently offlineAuae From United States of America, joined Apr 2004, 296 posts, RR: 3
Reply 12, posted (10 years 2 months 2 weeks 4 days 9 hours ago) and read 4058 times:

I remember hearing a while back that UAL had problems with the FWD galley area in their 777's and that floor beams were being affected, but I don't know what became of it. - Miamiair

********

I don't think the floor beams you are talking about are composite. There was a flexing issue at the cockpit to cabin joint. Unfortunately the design was borrowed from the 767, and suffered the same eccentric loading and bending problems that the 767 did. If you go on a 777, you will notice that you have to step up to get in the cockpit. It is that area that was a problem. Boeing / operators noted the problem early and released quite a hefty mod. Kudo's to DL MTC, they slammed through the first mod in 15 days and worked it down to 10. Their counterparts at another airline took 30 days to do the first and I doubt they ever got much better.

Shawn



Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
User currently offlineMiamiair From , joined Dec 1969, posts, RR:
Reply 13, posted (10 years 2 months 2 weeks 4 days 9 hours ago) and read 4064 times:

Thanks Auae for the info.

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