Milsabord
My guess is that the fact they were taking off from a very long runway at LHR with a lot of flat ground around may have had something to so with it. It could a been a very different result elsewhere.
Feeding in the wrong data is a very bad mistake and should have been caught. But the bit I find astonishing is that an experienced crew (Captain with over 16,000 hours) just watched the aircraft barely stagger into the air and didn't realise that something was (almost catastrophically) wrong. Why on earth did they not firewall (or TOGA or whatever it is called nowadays) the throttles? Are we in a situation that aircrew have so much trust or reliance or dependance on the computers that they are scared to over ride? As an ex pilot (DC-10, not Piper) and infrequent passenger I find that quite terrifying.