Fragile A380?

[BigHitDH]

I’ve been following the design and manufacture of the A388 with great interest of late, and just now a question popped into my head, which I’m hoping you guys might wish to comment on.

With the A388 design making unprecedented use of composites in the airframe structure, how are Airbus planning to protect the aircraft from perforations due to bird strikes/lightning strikes? We have all seen how lightning, birds and hail can completely destroy parts such as composite radomes, but Airbus are planning on using composite panels for major structural parts, such as the fuselage skin, and most of the THS and Vstab.

Airbus are using a large composite panel for the “leading edge” of the forward fuselage outer skin, extending from just aft of the cockpit to midway between the nose and the wing root. What happens when a 50lb vulture hits that at 250+kts, or if it takes a lightning hit?

Presumably these outer panels will form part of a normal pressure hull, so what are the consequences for maintaining pressurisation? From my (albeit limited) knowledge of the subject, composites tend to “shatter” (especially when cold soaked), whereas normal alloy type skins would leave a characteristic “petal” framed hole when punctured by, say, a bird impact. I can’t help but think that pressurising a composite hull to 9psi and then putting a gaping hole in it with 250kt airflow outside would have catastrophic results.

Any thoughts?

[swh]

BigHitDH,

A composite part is more damage tolerant than a metal part, the fibres in the composite provide alternate load paths.

Metal skin parts are also subject to the same forces in hail etc; however the grains in the metal can be damaged from heavy hail which generally will not cause the same level of damage on a composite part. The grain modification which is akin to hitting the part with a hammer would cause perminant change in the metal, and may result in slight damage to the gel coat on a composite part, however rarely local delamination.

The bird strike scenario is a greater issue in my view with metal parts over composite.

The real issues that have been developed recently is better interfacing between metal and composite joins, fasteners, and semi-monocoque composite design (i.e. removing honeycomb).

Don’t know exactly how the lightning paths have been designed, however this is something both Boeing and Airbus have experience with.

Was this a genuine question or a wind up ? many many fully composite aircraft are in service already.

[alexban]

Let's hope the vulture will be very scared by the huge building coming at him with tremendous speed at what altitude? :)
Then again ,I saw once a big hole made in a AN24 ,by a small seagull,and the AN 24 it's like a tank compared to the A388,so...
They must have thought about it,i'm sure.
Brgds Alex

[747FOCAL]

Better question is how do you fix the delam from the bird strike. You can't stick the whole plane in an autoclave.

This worries me on both the A380 and the 7E7. How does a mechanic accomplish a tap test on a suspected delam out on the ramp with all that noise?

This is sure to cause huge dispatch problems for both airplanes.

Southwest Airlines spent 25 Million dollars to design and certify aluminum replacements for the composite nacelle doors on their 737s because of the dispatch problems related with damaged nacelle doors. You also had to remove the engine to get the nacelle in the autoclave.

:sad:

[lomapaseo]

Not much of an impact vector force on any part of the aircraft that doesn't face forward.

Then again there has been lots of composite parts like slats that do face the oncoming bird.

Selection of materials is easily accomodated by design factors such as thickness and/or fiber layup. Even today's armor vests are composites.

[BigHitDH]

Thanks for the input guys.

Was this a genuine question or a wind up ? No, it was a genuine question!

Interesting point about the delamination, that's kindof what I was trying to get at, but you used the correct terminology!

747Focal, good point about fixing the composite structures. I presume with an alloy fuse skin if it's damaged you can cut out the offending section and rivet a new one in, how do they plan on doing that with the A388?

Are they going to need a cherry picker to do the walkround?

[lomapaseo]

Are they going to need a cherry picker to do the walkround?

About the same time that they use a cherry picker to check for meteroite damage to the tops of B747's:}

[itchy kitchin]

We now defrost the chickens before testing commences. Standby for more accurate data.

[Zoner]

It's been my experience that most damage is a result of jetways, belt loaders, fork lifts, and K-loaders. Freighters are especially susceptable. Look at any plane and the scab patches are really apparent. I think there will be a learning curve for maintenance but they'll figure it out.