The new Boeing 787 - How Safe? Living with composites on the ramp.
It’s great to see that Boeing is forging ahead with their ambitious 787. Hearing all the stories about the composite fuselage, and related long term savings to airlines is great. However, things never go exactly as one would like.
Ramp Rash - it's common for aircraft to be damaged during turn around.When you crunch an aluminium plane on the ramp, you know it. There is visible damage to the affected area. You are aware of the "need" to report the impact, no matter how small a dent you have made.What about composite fibre materials though? It is commonly known that these materials behave differently to metals. They can take great loads before actually breaking into pieces. I doubt that they dent like metals. Imagine if you can bump a ULD loader or baggage belt against a composite fuselage, and only see paint marks (and perhaps a few sheepish looking ground crew)? There exists the possibility that serious internal damage may have been done, but persons on the outside wouldn’t see that. Firstly, the possibility exists, that if large impacts still show no visible damage other than scratched paint, ground crew will probably keep quiet and thank their lucky stars that they didn’t properly dent the plane. Not great for safety.
Boeing's new 787 is using carbon-fiber composite material in place of aluminum for about half of each plane. Carbon-Fiber components are also used in Airbus aircraft. Despite their strength and low weight, composites have not been a miracle solution for aircraft structures. Composites are hard to inspect for flaws. Some of them absorb moisture. Most importantly, they can be expensive, primarily because they are labor intensive and often require complex and expensive fabrication machines. Aluminum, by contrast, is easy to manufacture and repair.
Anyone who has ever gotten into a minor car accident has learned that dented metal can be hammered back into shape, but a crunched fiberglass bumper has to be completely replaced. The same is true for many composite materials used in aviation. Aluminum is a very tolerant material and can take a great deal of punishment before it fails. It can be dented or punctured and still hold together. Composites are not like this. If they are damaged, they require immediate repair, which is difficult and expensive. An airplane made entirely from aluminum can be repaired almost anywhere. This is not the case for composite materials, particularly as they use different and more exotic materials. Because of this, composites will probably always be used more in military aircraft, which are constantly being maintained, than in commercial aircraft, which have to require less maintenance.
