HazelNuts 39,
I am sorry if the term "icing" confused the situation, it was a word Tim Vasquez used in his report I quoted from and I didn't change it. I believe icing is when supercooled water encounters a surface and then freezes. In the case of AF447, this was not the case. There was no supercooled water involved to the best of the weather expert's knowledge.
What I was attempting to say was the aircraft passed through a cloud or clouds containing ice crystals which, when coming into contact with wetted heated surfaces, can stick and buildup. I am very aware this phenomenon can and does cause problems with turbofan engines to varying degrees depending on a particular engine design. As Boeing studies have indicated, the ice buildup can both adversely affecting engine airfoil aerodynamics (power loss) and in severe cases, damaged compressor blading (ice shedding) or even cause combustor flame outs (water extinguishes the flame).
From what has been said so far by the BEA, the GE CF6-80E engines were not affected and performed in a normal manner. However, I am not so sure the pitot tubes did, they could have indeed clogged which lead to the erroneous speed sensing and eventually the AP/AT disconnect.
Indeed there is considerable testing done during the initial development and certification testing of new turbofan engines to determine effects of ice ingestion, large and small particles and shedding characteristics. I have seen it done in person on several occasions.
As Boeing points out, it is best to avoid areas of storms where ice crystals are present as the volume tends to be unknown and onboard weather radar may not detect the presence of ice crystals at all.
I stand to be corrected on any of the above.