Originally Posted by
roulishollandais
@Hazelnuts39
What is still unknown is the altitude read on the altimeter on the cockpit
I think this has been covered before, but if I may attempt to recap...
The only way to be 100% certain would be to have had a camera trained on the PFD, but since we don't have that, a degree of assumption will always be necessary. Folks, correct me if I'm wrong - but I think from recollection of the AF447 thread that the DFDR altimeter trace is fed from the ADIRU selected on the Captain's side (LHS).
As others have demonstrated, the DFDR trace seems to tally well with other data when it comes to actual baro altitude. QNH seems to have been correctly set, and all things considered the likelihood is that the baro alt on the PFD was showing the values recorded on the DFDR. For there to have been a discrepancy would mean a fault on the data bus between the ADIRU and the LHS PFD, for which no evidence seems to exist (though, admittedly, such evidence would be difficult to trace later on).
Asseline insists that the baro alt was reading 100ft throughout, and furthermore frames the possibility that it wasn't as tantamount to accusing him of lying. He mentions earlier baro alt misreadings on test flights and argues that may have happened in this case. I believe he states elsewhere that he was relying on the baro alt and external references because he found the digital RA display difficult to read.
I'm sure that Asseline believes fervently that the baro alt was reading 100ft, and if it wasn't, he may have still perceived it as such through confirmation bias - as the workload on the flight deck was significantly higher than anyone had anticipated due to the briefing errors. If the baro alt was in fact consistent with the DFDR, that doesn't make him dishonest - it just raises the possibility that he made a (completely understandable) mistake under pressure.
On the other hand, his own input raises further questions about the conduct of the flight as a whole - particularly with regard to the wisdom of relying solely on one instrument if you consider that instrument to be unreliable, with the only safeguard being external references at an unfamiliar airfield.