More Structural Issues in the AF 447 Crash

| Tue Jun. 9, 2009 3:00 PM EDT

In response to the loss of Air France 447, a French pilots’ union today asked its pilots not to fly the Airbus 330–the design of the crashed plane. Much has been made of the possible pitout tube failure on Air France 447. These tubes are sensors on the wings which might be prone to freezing up and distorting air speed, which in turn might mean the pilots were flying at too slow or too fast a speed to get through the thunder storms in the region.

There is a different theory having to do with the plane’s possible structural flaws, which brings us back to the question of composite aircraft materials, which I wrote about last week. Parts of the tail, recovered Monday, appear intact; the tail looks like it was ripped off the plane at the points of attachment. You can get some idea of what it looks like from thisFrance 24 video.

To some observers, this bears a striking resemblance to the loss of the tail in the devastating American Airlines 587 crash in New York in November 2001. That plane was an Airbus 300. In an interesting comment on the Whatsupwiththat blog, a reader, Adoucette, writes:

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The disturbing thing to me is that the A330 design is derived from the A300. Both have composite tails. In the AA-587 crash in Nov of 2001, the NTSB blamed the failure of the A300’s composite tail on the co-pilot. The NTSB claimed that the pilot made dramatic rudder inputs to counter wake turbulence from a 747 which had departed Kennedy two minutes earlier….
The NTSB said that the pilot, to combat mild turbulence, over controlled the aircraft by swinging the rudder fully to one side and then all the way to the other side, and it was this over-control which exceeded the tail’s design limits….

Now if this is possible from rudder inputs in mild turbulence in clear air at relatively low airspeed over NY, consider what could happen at high speed in major turbulence over the ITCZ [Intertropical Convergence Zone, a storm-prone area where trade winds converge].

Also making its way around the web is a report from NASA’s Langley Research Center on the possible effects of lightening on composite aircraft:

Traditional aircraft act as Faraday cages when struck by lightning, which means that the charge stays on the exterior of the aircraft.  However, as more aircraft are built using composite materials, we will need to understand the direct and indirect effects of lightning on those aircraft.  The researchers at LaRC are studying the  hazards of lightning on composite aircraft.  Some of the issues include the fact that magnetic flux can penetrate avionics wiring, and that lightning damage is often more severe than tests would predict (see this presentation for the full discussion).  Magnetic flux can penetrate composite aircraft more easily than metallic aircraft, inducing voltage and current on avionics wiring.

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