Something to make one pause before boarding Airbus' new super jumbo A380 is how they saved weight. Fully 40% of the wingbox which ties the wing with the fuselage is made of carbon-fibre composite. It keeps the wingbox strong while saving weight. Less weight means more cargo and passengers carried with greater efficiency. That is the good part. The bad news is when composites delaminate without any external signs.
Ask the passengers of Air Transat Flight 961 aboard an Airbus A310 in 2005. Their composite rudder parted company with the rest of the airplane at 35,000ft. Thankfully the crew was able to safely land the plane sans rudder. Or when FedEx did some ground tests on one of their A300s in 2002 because a pilot reported uncommanded rudder movements. The rudder actuators tore through their mount points in the composite rudder.
Airbus insists that visual inspection of composite parts is all that is needed to detect any problems. Others disagree and insist on ultrasound being used to detect delaminations invisible to the naked eye. Prof. Williams of MIT thinks the cycles between the frigid temperatures of high altitude flying and that of sea-level causes moisture trapped between layers to go through freeze/thaw cycles creating gaps that are invisible to a visual inspection. It seems ultrasound is taking hold as the inspection method, but what happens when the forward bulkhead of an A380 wingbox is detected as delaminating? Scrap the whole plane or take it all apart to fix it?
And Airbus has made 40% of the A380 wingbox out of composites. Something to think on when selecting a trans-oceanic flight.
4 comments:
I wouldn't want to travel on an A380 for a lot of reasons, not the least of which is the "crowd-killer" aspect of the behemoth. But the carbon fiber laminate issue would be pretty low on my total list.
Laminates have been in use for a long time. B777 uses a lot and the B787 "Dreamliner" is almost totally laminates. Not a great concern.
Ultrasound has also been in use for maintenance inspections. Longer ago than I would readily admit we called the operation NDI or "non-destructive inspection". It involved things like magnetic flux inspection gadgetry, X-ray, ultrasound and lots more techno-babble.
I was merely an operator, but I bet my life on the efficacy every time I used Uncle Sam's equipment.
I admit its a low priority, it just struck me after seeing a show on the A380 about how wise to have such a critical and inaccesible part made of so much composite material. NDI, dont forget running the oil from the jet engine to see what kinds of metals were in it to find out where the engine was about to fail. Or boroscope inspections.
And yes an A380 would be a 500 person killer if one failed. Not a very cheery thought with all the recent Airbus accidents.
As for the effects of continual repressurizing, a reminder. Aloha 243. BTW, I saw the plane the next day in Wailuku.The most incredible thing is how well the passengers and flight crew reacted. Read the story.
http://www.aloha.net/~icarus/243pg2.htm
Yep that Aloha flight was amazing, the crew got the 737 on the ground after that with only one fatality. Until that 2005 Airbus, composite materials on airplanes were thought well nigh indestructible and mere visual inspection sufficed. Like everything else, theory sometimes falls short of reality and people pay with their lives. We can go back to the deHavilland Comets exploding in mid-air and the fault lay with their square passenger windows inducing cracks during the press/depress cycle.
Post a Comment