It seems to me they were unable to stop the descent....that is not indicative purely of instrument failure but also of controls not responding
Some here think they could have flown these monsters simply with cable assist like a wounded B 17...
I don’t know....i think we have some pond crossing pilots here.. Maybe they know
Its a court battle now over liability so we can expect fussilades from both sides
http://www.bea.aero/fr/enquetes/vol.af.447/note29juillet2011.en.pdf