80/20,
You are correct, but when operating in such conditions we have to accelerate the engines to a mid-power setting to centrifuge the ice off the fan every few minutes....the RR Trent has a more complex procedure but the outcome is the same. Do you have a more limiting operating procedure?
idg
Not really - idg, Boeing introduced a pre-takeoff 70%N1 static run-up procedure after a freezing fog situation where most airlines cancelled all flights but a few decided to depart. Many of the departing carriers experienced severe vibrations which resulted in 12 CFM engines with serious blade damages.
The static run-up might help, but there continues to be cases where the fan icing is too severe to be shedded. Some airports, experienced with this problem, offers a procedure where engines are shut down, front covered and heated by hot air and inspected just prior to takeoff.
I once observed thick clear ice on each fan blade and an “icicle-like" spear of clear ice the size of a small coke bottle sticking straight out of the spinner after only 5 minutes of taxiing in freezing fog. Freezing fog got my respect since it can cause rapid fan icing too severd to be sheeded without engine damage.
It can even be just fog which becomes freezing fog as pressure drops (expansion cooling) in the engine inlet.
BOAC,
Do you use Type IV fluid in Europe now? Seems to have even better holdover times than Type II.
Both are used in Europe, IV will give better protection around freezing, but both II & IV can give you as little as 15 min freezing fog HOT (hold-over-time) at colder temps. The freezing fog that I have encountered has always been below -5°C with very strong inversions.
The real 'nasty' is freezing RAIN and you wouldn't catch me even attempting to taxi in that...
FullWings... I agree 100%