[pfflier]

I was ambiguous when I said systems in my last response because I was was referring to the pilot-airplane control interface systems which I didn't explicity say.

No modern fly-by-wire design has a single point failure mechanism in any aspect of flight control systems.

The FCS controllers are typically triple redundant and the control system actuators also have redundancy.

In addition reliability testing is done to the nth degree on all electro-mechanical systems that actuate flight control surfaces.

Aircraft break-up, serious design flaws, serious software errors or pilot error are realistically the only things that could compromise the systems.

Entering weather, even thunderstorms would likely not be the cause of the crash, just a contributing factor. If the pilot lost his plane solely due to the thunderstorm, then, again it is pilot error because he made a bad decision to penetrate the storm.

My bet on the outcome of this investigation? The finding will be pilot error.

[expat2]

I consider myself quite knowledgeable on the subject of redundant high-reliability FCSs.
It is true that a TMR system is pretty reliable (provided each channel has different software) if you can guarantee that you will never have more than one fault at the same time. However, in a double-fault situation, the FCS operation will breakdown (as appears may have happened in the Brazil crash). There is also a failure mode called the Byzantine Generals problem that it cannot handle. TMR is Ok for say mail/FedEx and military aircraft, but others feel it is inadequate for airliners.

[expat2]

I should add that you are probably right when you say that it will probably be called pilot error, anyway. The airline manufacturers such as Airbus bring intense pressure to bear on not blaming their product. The $$$ involved in that blame issue are enormous. IIRC the Brazil crash was blamed on pilot error, even though the pitot-head design was faulty and screwed up the air data input to the rest of the FCS.