The transcript of the CVR from ill-fated Air France flight 447 has been published. It’s reprinted here with running commentary. A minor sensor failure started the whole error chain, and then the cockpit crew spent a staggering four and a half minutes doing everything wrong: they handled a stall incorrectly, they ignored/disbelieved their instruments, and failed badly at the fundamentals of crew resource management.
There was, however, a conributing factor that I’m struggling to understand. The article indicates there are two joysticks for flight control, one on either side of the cockpit. Whereas a traditional control system provides two yokes that are mechanically linked and clearly indicate to both pilots what the position of the controls are, the fly-by-wire system on the Airbus A330 allegedly does nothing to communicate one pilot’s inputs to the to other. The reported strategy for dealing with differing inputs from the two pilots is to calculate the average position of both joysticks and use that average as a single control input. In the case of Air France 447, one pilot was quietly pulling back on his joystick for most of the descent (holding the aircraft in a stall) while the other pilot remained baffled as to why the plane wasn’t nosing over in response to the full-forward input he was providing on his own joystick. If the article is correct, then the system averaged both inputs into something close to a zero value for elevator control.
Can a professional pilot or aerospace engineer confirm whether the article has this right? That is, does the A330 really use the average of both joysticks to generate a single value for control input? If this is the case, given that it appeared to contribute to this horrible air disaster, what is the rationale for designing a flight control system this way?