Originally Posted by
jcjeant
You have two probes .. three probes .. certified or modified (and certified again) .. when they will find it in the right environment (air freezing or ice particles) the greater the chance that they will all be put out of function
So .. 2 probes .. double failure ... 3 probes .. triple failure ....
It's a question of systems safety. The aircraft were originally certified with the Goodrich pitot tubes fitted - there has never been a triple failure with this setup. The Thales option was introduced later and was certified independently - maybe someone can confirm whether this did or did not involve being certified in situ as opposed to just in the lab.
Nevertheless, there turned out to be something inherent in the Thales AA design that made it more susceptible to precipitation blockage than the default Goodrich fit.
A question was asked regarding why these problems seem to be confined to a time period a decade or so after the introduction of the A320 and her sisters - I'm just supplying one potential reason as I've understood things.