Not quite correct....
Not quite correct: Ice cannot form when temps are below -40c.
Please read the Airbus FCTM with regard to this. You will find that
the procedure is to NOT use anti-ice systems during climb or cruise
when the OAT is below -40C except when flying in areas of CBs.
So, with this, there is to be noted exceptions to this "minus 40 rule".
First, this applies only to climb and cruise. Second, this applies only
if not in the vicinity of convective activity.
Other posts, so far, list the reasons why......
Fly safe,
PantLoad
post script.....It was SOP at my former company (I've retired several years ago.) to follow the above-mentioned rule. And, we flew the Boeing
(with JT8D, CFM 56, and CF6) as well as Airbus (with CFM and Pratts on the 330).
By the way, there was an excellent article from Airbus....will try to find it...about flameouts at high-altitudes on CF6s. What was happening
was, during initial descent, at temps well below -40C, the engines were
flaming out. If I recall the article, it mentioned that most of the events
occurred in tropical climates where CBs were present. In every case,
engine anti-ice was not selected at top-of-descent....when in visible
moisture...but OAT less than -40c.
Interesting.....