CONF iture, Nigel On Draft
if you keep your prejudices out you will understand the accident better. I am correcting some of your assumptions.
1. Where did you see "clear indications" ?
There was none.
Yes there were. AOA sensors 1 and 2 were blocked at earlier values when they froze and got jammed. Same values are shown on PFD1 and PFD 2 as V alpha prot and V alpha Max after converting them to speed and that display was wrong. Below I quote BEA report.
"However, the blockage of angle of attack sensors 1 and 2 at identical values had inhibited the functioning of these protections and led to an erroneous display of the characteristic speeds of these protections."
2. The system decided to silently discard the only reliable AOA data. When you realize the importance of the AOA data for the Airbus and its protection system to work properly, the logic would be for the system to at least advise the crew as soon as a significant difference between the AOA readings is identified.
Nothing gets silently discarded. This is known as self detected failure and is intimated to the crew as ADR3 fail on ECAM . However in this case it discarded ADR3 in preference to the erroneous ADRs 1 and 2 in accordance with two versus one principle and since it treated it as a single failure normal law was maintained. Such a possibility is explained in FCTM. It defies logic that when there is evidence that some thing is fishy about the ADRs(speed display and rejection of the 3rd) from which the protection arise ,the crew proceeds with protection tests at a low altitude of 4000ft without any preparation. That deprived them of the crucial time they needed to analyse indication of USE MANUAL PITCH TRIM which indicates direct law and its implications.However this is not going to change your dis Confiture about the Airbus and you are habitually going to say "it doesn't matter". That is your privilege I am just presenting the facts.
Last edited by vilas; 18th January 2015 at 08:49.
Reason: correction