I beg to differ on your comment.
QUOTE
Just maybe Airbus squeezed the specs just a little too tight, and ended up
with pitot that are fine nearly all the time, but without enough reserve
heating energy for every case of high altitude icing conditions.
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Please go back to BEA interim report #2 page 63 :
QUOTE
The set of icing tests to be performed to meet the Airbus specification includes
26 test points in all (10 for covering appendix C and 16 additional tests), thus
covering a wider envelope than that defined by the JAR25 regulations.
The Airbus specifications used for the certification of the probes are therefore
stricter than those of JAR 25 (annex 4).
UNQUOTE