Howdy All
This is slightly off topic and while it's a problem that affects thrust - I can't see how it bears on BA38, since they had commenced final approach and I'm sure that crew advanced thrust manually. However it's something worth highlighting for those operating the 777, particularly instructors who should be pointing this out to students in the sim.
I believe there is a software anomaly in the 777 thrust limit
setting system which in specific situations can limit auto-throttle thrust below that required to maintain level flight. Details can be found in a document I wrote a while ago on my web site at
http://www.infinidim.org - direct link is
http://www.infinidim.org/Docs/Thrust...ly%20Brief.pdf
Essentially it revolves around the FMC setting CRZ thrust on approach when VNAV is engaged after flaps have been extended, when according to the Book GA thrust should be annunciated. In specific situations (Engine Out, Gear Down, Flap 20, Hi Weight, Hi OAT) this results in insufficient thrust to maintain height. I have advised my company's management, and Boeing about it a few years ago, but the issue is still there - whether it's a fault or not seems to be in dispute.
I know, I know - this doesn't relate to BA38. It sounds like they pushed the thrust levers up above what the autothrottle was commanding, and did not get a reponse.
However two points to be made are that as good as the 7 is, it's not perfect - maybe that's why we're still there - and when you reach down and push the thrust levers, you should get the thrust, whatever automatics are engaged. A Pilot's aeroplane.
Regards.