Originally Posted by Rainboe
No. Below -40 degrees C, ice does not form anywhere on the fuselage or engine. It is practice to never turn on engine or airframe anti-icing below -40 degrees C.
If I were you, I'd do my homework before spreading falsehood.
The problem among our pilot community is that we actually know little about ice particle (or ice crystal) icing.
For those flying on the bus, FCTM says to turn Engine Anti Ice ON when flying near CBs even if SAT is <-40°c ! that's mainly because of ice particle icing (e.g. in an anvil).
Thalès pitot probes -AA (AF447) series seemed very sensitive to that particular phenomenon, given their ASR history.
Most Ice particle types are not detectable by Wx radar. When in it, pilots are often misleaded by the sound of melted ice particles on the windshield (if any) that is wrongly interpreted as rain or hail...
Ice particle phenomenon is quite a new study field (less than 5 years). Those MET conditions being very difficult to recreate in a lab, thus modeling.
In flight, as said by safetypee, it's usually around deep convective cells.
I suggest these readings:
Ice particle threat to engines in flight
FSF article about Ice Crystal Icing
PPS by Jeanne Mason, a (the?) specialist of ice particle icing
Correct course of action...
I would say it depends on the icing severity. Sometimes it could as subtle as an anomalous TAT reading that you won't even notice in cruise.
In a case of powerloss, with EPR engines, it could be difficult to discriminate between an actual icing of compressor stage(s) or just a severe TAT cloging.
I would say, (E/AI ON, disconnect A/THR) get out of those conditions first (descend most probably), see after.
But I am not Mr Airbus or Boeing, so...
