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747FOCAL
29th Jan 2004, 22:59
Aerospace Notebook: Airlines cautious on 7E7 composite
Seattle Times 01/28/04
author: James Wallace
(Copyright 2004)


Emirates Airlines, fresh off the largest single jetliner order in history for Boeing and Airbus jets, has acknowledged that it is a possible customer for Boeing's 7E7.

But The Boeing Co. is going to have to prove to the Dubai-based carrier that the composite fuselage of its new superefficient plane will be able to stand up to the usual fender-bender mishaps that often occur with planes parked at airports, an Emirates executive said.

Aluminum-skinned jets can be dented by baggage trucks, boarding steps or those high loaders that are used to service planes -- everything from taking garbage off to putting food on.

"Our maintenance boys have been particularly hard on Boeing, given the extensive use of composites that will be used to lighten up the Dreamliner," Tim Clark, president of Emirates Airlines, said in a telephone interview from Dubai last week.

The Dreamliner is the name Boeing has given its 7E7.

Boeing is now out hunting for orders for the plane so development can officially begin this year, with entry into service in 2008.

The 7E7 will make extensive use of lightweight composites -- more than any previous commercial jetliner. The fuselage and wings of the plane will be composite.

This will make the 7E7 as much as 30 percent lighter per seat than current jets, Clark said.

But there may also be a drawback to having an all-composite fuselage, Clark said: ground damage. The hard, plasticlike material doesn't dent like aluminum, so some airlines, such as Emirates, are concerned that damage would be hard to spot.

Emirates, the fastest-growing airline in the Middle East, sees ground damage to its planes as much as a dozen times a day across its network, Clark said.

Usually, those planes don't need to be taken out of service for repairs because the damage is not serious, he said.

"But with composites, my understanding is you need to treat it immediately," Clark said.

"Boeing told us they have dealt with this issue. I said that's fine. But I can't afford to have aircraft stuck on the ground because of a small dent, which on other aircraft I would let go, but on the 7E7 I can't because of the composite material."

Boeing said this should not be an issue with the 7E7.

"The 'bangs' that cause minor damage to aluminum structure will not impact composite materials," Boeing said.

The composite material for the fuselage of the 7E7 will be the same as that used on the tail of the 777. Boeing said it has never had a maintenance issue with the composite tail of the 777, of which more than 400 are in service.

"If the damage is not visible (with the composite material to be used on the 7E7), the structure is sound and can be used," Boeing said. "Our service manuals will explain this in detail and also provide operators with directions for what to do in case of visible damage. We are meeting with the airlines around the world to explain both the structural- monitoring and composite-repair technologies."

Boeing plans a nervelike system of sensors that will be embedded in the composite structure of the 7E7 to provide constant data about the health of the plane. Damage-prone areas around cargo doors and catering doors will have these sensors.

Boeing is evaluating a couple kinds of sensors, including an optical one.

"Our approach to using structural health monitoring will provide excellent awareness of the health of the composite fuselage," Boeing said.

"This combination of structural- integrity monitoring and a more robust material system offers a dual advantage -- higher resistance to damage and better awareness of any damage that does occur."

Boeing added that as airlines learn more about the new 7E7 technology, concerns such as those expressed by Clark will disappear.

Clark said Boeing provided Emirates a two-hour briefing on the 7E7 just before the recent Dubai Air Show.

"We have already expressed a fairly strong interest in the plane," Clark said. "I say fairly strong because I've only seen a paper plane. ... But it looks to be an absolute beauty.

"I'm sure that it will be a wonderful machine," he added. "But the proof in the pudding is in the eating."

Dubai is the second-largest of the seven states that make up the United Arab Emirates. The government there is transforming Dubai into a world- class destination resort, and the ruling Maktoum family, which owns Emirates, has not been shy about spending money to make Emirates one of the world's top carriers.

At the Paris Air Show last year, Emirates placed a record order for new planes, worth $19 billion at list prices. It ordered an additional 21 Airbus A380 superjumbos and will lease two more. That brought to 45 the number of the double-decker 555-seat planes that Emirates has ordered.

Emirates also ordered long-range A340-600s and A340-500s from Airbus, and said it will lease 26 Boeing 777-300ER jets -- Boeing's next long-range jet, which is about to enter service.

The 7E7 will be a widebody jet smaller than the 777. It will carry 200 to 250 passengers.

Clark said Emirates would prefer the 7E7 have more capacity.

Still, the Maktoum family has made clear its interest in the new Boeing plane.

"If the price is right, and the economics are right, I could see that plane operating to city pairs that perhaps we had not planned to do before, perhaps second- or third-level city pairs in the United States," Clark said.

But Boeing is going to have to convince Emirates, and probably other airlines, that the composite skin of the 7E7 will hold up to the bumps and dents that jetliners experience when they are not flying through the sky.

Daysleeper
30th Jan 2004, 00:36
not sure i understand the comment by boeing about the tail, dont often get impact damage from trucks there.

747FOCAL
30th Jan 2004, 00:44
Imagine trying to do a tap test check for composite damage on a commercial airport ramp with all that noise going.... even worse the noise, blowing snow, and it's dark. :}

Lu Zuckerman
30th Jan 2004, 06:29
What Boeing says may be true but then again it may not.

The following was extracted from several of the above posts.

Those comments will be followed by my comments.


The hard, plastic like material doesn't dent like aluminum, so some airlines, such as Emirates, are concerned that damage would be hard to spot.

"The 'bangs' that cause minor damage to aluminum structure will not impact composite materials," Boeing said.

The composite material for the fuselage of the 7E7 will be the same as that used on the tail of the 777. Boeing said it has never had a maintenance issue with the composite tail of the 777, of which more than 400 are in service.

“Not sure I understand the comment by Boeing about the tail, don’t often get impact damage from trucks there”.

About ten years ago in the Boeing Everett facility an overhead crane was transferring a large jig/fixture. In the process of moving it a corner of the large metal fixture struck the composite tail of a 767 which was being assembled. The operator immediately contacted the production manager and he sent a man to inspect the damage. The crane operator said it was a glancing blow and he did not see any deformation. The man that inspected the tail indicated there was a minor abrasion of the composite skin and that the skin had not been damaged.

A short time later a composite repair technician inspected the damage. His job was to repair any damage incurred during production. He told the production manager that he was going to inspect inside the tail. He went inside and found that where the composite skin had been hit the inside structural ribs that were bonded on the inside of the fin had been ripped off from the skin and were damaged beyond repair. The fin had to be removed and a new one installed.

True, it wasn’t a truck but then again there are inspection stands that could cause similar damage.

Here is another point to ponder.

Boeing stated that they have incorporated embedded sensors that will detect damage. I can only assume that any indication of ground incurred damage will be made available to the pilot as well as the ground technician. If it has been determined that some level of damage has been incurred, does the download to the ground technician, or the information made available to the pilot, does the system pinpoint the damage location. And does it indicate that the plane can be dispatched with the repair being effected at the home base. Or, does the system determine that the damage is so severe that the aircraft must be repaired prior to the next flight. Who will make the repair and how long will the aircraft be listed as AOG?





:E :E

Torquelink
30th Jan 2004, 19:18
Lu,

Thought the 767 had a metal tail?

Midnight Mike
30th Jan 2004, 23:31
Are these same composites that the US Navy has been using in their fighter jets? Or is it a new type?

747FOCAL
31st Jan 2004, 16:25
Oh come on now, everybody knows about the metal bucking bar that was left in the 767 tail during assembly and for two year after it was delivered the stews kept complaining about the banging noise in the back of this airplane. the noise was never there in others. Upon inspection they found the bucking bar and that airplane ended up coming back to the factory for a new tail if I heard correctly. :ooh:

cwatters
31st Jan 2004, 23:45
This problem first appeared on cars. The rapair shop would look at a car and estimate the repair cost. Then later when they removed a fender/bumper with light damage they found the body work bashed in underneath.

It's possible to make very small glass microbeads these days (they are mixed into resin to make light weight fillers). I was wondering if a version filled with dye could be laminated into a composite structure. So that when "dented" the composite would "bleed" and the dye make any damage visable?

Oh bother - there goes my chances of getting a patent.

Bre901
31st Jan 2004, 23:52
cwatters

Edit or Delete your post !
I'll keep quiet for 10% of your earnings :E

Huck
1st Feb 2004, 09:38
Filler in the states is marketed as "Bondo." In high school I was known as the "Bondo Bandit."

Lu Zuckerman
1st Feb 2004, 22:57
To: cwatters

Some high strength aircraft bolts have a dye inside of the shank. If a crack develops the dye will seep out letting the A&P/LAME know the bolt is in the first stages of total failure.

:E :E

NWSRG
23rd Jan 2005, 01:04
Adding to an old thread, but anyhow...

What will happen the 7E7 if it gets struck by lightning? I have seen pictures of composite aircraft structures which were punctured by lightning...presumably Boeing have thought of this possibility, but does anyone know what precautions they will take?

Out Of Trim
23rd Jan 2005, 04:56
What the hell is a " Bucking bar" ???

BEagle
23rd Jan 2005, 07:43
"If the damage is not visible (with the composite material to be used on the 7E7), the structure is sound and can be used," Boeing said.

I thought that was precisely the assumption which must never be made with composites?

mustafagander
23rd Jan 2005, 09:57
As I recall it, Out of Trim, a "bucking bar" is a hunk of steel used to hold against the tail of a rivet being driven to peen it over. It is used at the other end of the rivet from the rivet gun. They can be rather heavy.

toon
23rd Jan 2005, 10:29
Perhaps the pilot of the future will be issued with a can of Isopon P38 and some fibreglass with which to effect the repair ?

:8

four_two
23rd Jan 2005, 11:30
As I recall it, Out of Trim, a "bucking bar" is a hunk of steel used to hold against the tail of a rivet being driven to peen it over. It is used at the other end of the rivet from the rivet gun. They can be rather heavy.
Or in plain English "a riveting block"

swh
23rd Jan 2005, 13:43
BEagle,

Composite material is more damage tolerant than metal, alternate load paths can be taken in the material at the matrix in which the fibres are in can transfer load to other fibres.

The biggest challenges with composites are with mating to metals (prevent corrosion), and how to fasten them together.

Another aspect which is normally associated with honeycomb filled control surfaces is water injection into the core, which expands as water freezes, and normally results in the delamination of the skin from the core with time.

:ok:

hobie
23rd Jan 2005, 15:29
"Bucking Bars" are a bit like Aircraft :confused:

..... they come in every shape and size :p .....

try a Google search ....

http://www.google.ie/search?hl=en&q=bucking+bar&btnG=Google+Search&meta=

:ok:

mscar
23rd Jan 2005, 21:27
"If the damage is not visible (with the composite material to be used on the 7E7), the structure is sound and can be used," Boeing said.
This is a very unusual statement by Boeing.Composites when compared to aluminium require much more careful examination after impacts as the damage can be within the composite layers.
Are they planning on using a new form of composite unheard of to the industry that shows up damage or what?:confused:

Blacksheep
24th Jan 2005, 04:53
A couple of years ago we had a B767 hit by a runaway tractor. It took out the whole belly skin below the forward cargo bay and it cost around eight million quid to fix it. The nature of the impact was such that it would definitely have taken out the belly of even the toughest composite aircraft. There have been plenty of similar accidents before and there will be many more.

Then there's the possibility of severe structural damage that isn't immediately apparent. Composites may be more damage tolerant than metal but dents in metal are very obvious: even if missed, the slow rate of crack propagation gives ample opportunity to catch it before catastrophic failure occurs. Composite structure tends to let go with a sudden loud twang, as it were, and little advance warning - when it does go, it really, really goes. Also, I can't imagine the autoclave that will take an entire fuselage, so I imagine we are talking about hot-bond repairs. On a large area of damage, a hot bond repair will be a major undertaking with the aircraft out of service for a very long time. And are we going to keep huge amounts of repair material on hand, just in case? It has a relatively short shelf life and costs several arms and legs.

So, the next question is, even if the manufacturers and operators are happy with an all composite fuselage, how do the insurers feel about an aircraft fuselage that would probably be BER in the event of a significant ground incident?

Then there's the wings. Oh yes, of course. They're not a problem because the wings never get damaged in ground accidents.

Ooops! :uhoh:

NWSRG
24th Jan 2005, 12:53
Can anyone comment on the effects of lightning on the 7E7 structure?