But will the computer let you go to Direct Law? One of the problems with the Air France flight was it switched laws without them realizing it. I'm sure the pilots tried to put it in whatever mode is most like no computer intervention. And from the wikipedia article, it sounds like Direct Law isn't completely direct: the "maximum deflection of the elevators is limited for each configuration as a function of the current aircraft centre of gravity," which sounds like the computer still has some control.
I'd be surprised if the AF447 pilots didn't realise the aeroplane had reverted to a set of laws with fewer protections, as that was why the autopilot disconnected in the first place. If the autopilot spontaneously disconnects your first question is presumably going to be why.
Then again, I'll probably never understand what the pilots of AF447 were thinking, and their actions lacked coherence. But I would expect a perceptive pilot to notice the change of law. Especially given the stall warning - normal law has full stall protection, so AFAIK hearing a stall warning is strongly indicative of non-normal law.
AFAIK pilots can always revert to direct law by disabling the primary computers on the overhead panel. The article is curious though, because it states the pilots tried to reenable the third primary computer after it failed, which resulted in a second dive. They gave up on restarting it after that, but left the other primary computers engaged, but were concerned about whether the plane would behave. My (potentially misguided) instinct there would be to throw out the primary computers altogether as a precaution.
It wouldn't surprise me if Airbus training encouraged pilots to always try to return to the maximum level of automation and envelope protection after a failure. In that context - the context of Airbus's culture - deliberately reverting to direct law could be seen as irresponsible, even if it seems like the opposite could be said to be the case in this incident. If so, it'd just be another way in which Airbus's approach to aviation raises questions...
Prior to these accidents pilots were trained to avoid stalls and unusual attitudes rather than learning how to recover from them, not least of which is lack of simulator fidelity when outside the flight envelope, which was cited as a factor in the AF 447 accident. While they did know alternate law applied, they didn't know why and the flight computer didn't give them sufficient information to figure this out quickly, and the indications they were getting (speed, attitude, c-chord warning, stall warning) pretty much confused all of them.
