I don't think an electronics failure is more than a red herring in this case.
If we look at the course of the events, it's rather more possible that they just did forget to retard the #2 TL.
However, and that's my whole reason to actively join this discussion, it should be carefully looked at
a) why this has happened and
b) why it could develop into such a disaster.
Even if bsieker will shoot me again for saying this:
The non moving throttle levers have their share in making this possible, and for three reasons: first, if they were moving with AT (or flown manually) there's just no possibility that they would be sitting in the CLB detent. Very simple, no room for error.
Secondly, moving TLs are feeding back aircraft actions using two additional sensory channels: peripheral vision (specifically sensitive to motion) and tactile, when the pilot has his hands on the lever.
Thirdly, and a little more "meta", the way the throttle quadrant works here is different from most other civilian aircraft, to say the least. Retarding the levers to idle really has nothing to do with bringing the engines to idle, they are already very close to ilde by the AT It's a metaphor for the pilot to tell the plane "we are committed to this landing". It really disconnects the AT and enables the GS and AB system. Unlike the Boeing design, the same TL also controls the reversers, which might have added to the confusion in this case.
I think it's a very reasonable hypothesis that the pilots might have been in some kind of "tunnel vision", having the inop TR on the tops of their minds, focusing on the one TL only and the fact that only this one should be brought into reverse and over that leaving the other one where it was all the way.
Is this a bad mistake? Sure.
Now, as they touched down in that configuration, the PM called out "no spoilers". Another alley into tunnel vision. Everybody on here knows the remedy for that no problem by now: bring back that thrust lever!
They were focussed on spoilers. So what did they touch? The spoilers lever, effectively disarming the spoilers. What were they hoping to get? I don't know. But I find it very reasonable that, if a system you expected to work fails, you first touch the controls for that system. Then, when they concluded that they were not getting any deceleration, they applied manual brakes (and thank you PBL for debunking the 11s myth brought up earlier) and were hoping for the best which, as we know, did not happen.
So here they are, plagued with two problems:
- no spoilers
- no autobrake
What do they touch? The controls for those two systems. Natural. Tunnel vision.
And all the time they seem to have been oblivious of the root cause: the trust lever.
Could a system be designed to be more forgiving of this root error? I say it could. A manual option to deploy spoilers and thus commit to the landing might have helped, or, the other way round, a system that deploys spoilers on manual braking.
I have actually no idea if or if not Boeing has similar issues in their a/c design and it doesn't matter either. I'm not comparing one over the other because I would have any sort of preference. I'm looking at this from a human / machine interaction point of view.
When an Airbus official then sais "the plane has performed as designed" I can't help thinking that this sentence has a certain cynical sound to it. Almost as if "design" was out of the realm of what should be looked at.
pj