http://www.pprune.org/rumours-news/4...ml#post6505825
safetypee:
Roger your post. I had asked, in this thread or the other, about TAT probes being ice obstructed, and you provide me an answer. Report saved FFR. Thanks.
Vovachan; lonewolf, re “assumed ALL instruments were suspect/wrong”, but ‘not likely’.
Not likely, but don’t discard the thought.
See another A330 Incident where unreliable airspeed (pitot probes freezing) resulted in an apparent change in altitude (assumed low speed correction factor).
300 feet off. (The ATSB document you linked to) Not quite the altimeter unwinding, is it?
However, perhaps the point you are making is that seeing alt low a few hundred feet (from an iced TAT and iced pitot probe) prompts pilot to make what is initially a small correction to climb back to FL350? Is that what you were getting at?
If the crew’s perception was of a ‘failure’ of airspeed, sudden drops in altitude, and perhaps rapid changes in VS, then concluding that there was a ‘display’ failure (the computation behind displayed parameters) would be logical.
But not the attitude indicator, which is what I had in mind primarily when I made my response. Sorry for the ambiguity, I had thought I was addressing how pilots tend to know which systems influence which cockpit gauge ... but I guess I did a poor job.
ADIRU includes IRU. IRU does not use airmass data to display attitude. Have I missed something?
The ‘increasing’ temperature could have been due to the TAT probe blocking with ice crystals, again see the A330 incident above.
I may have asked that in the other thread. Thanks!