From the FCOM :
Flight in icing conditions :
Engine anti-ice :
ENGINE ANTI ICE must be ON before and during a descent in icing conditions, even if the SAT is below - 40° C.
How do you the interpret the above ?
Situation :
You are approaching top of descent in (day) VMC (not in icing condions at the moment) and well above the cloud (10'000' or more) with an SAT below -40 (ie. -56) at the moment. You will eventually encounter icing conditions later on in the descent.
1 interpretation :
You must select engine anti ice on NOW before commencing descent even though not in icing conditions at the moment but you eventually will be.
This is because the quote says "before and during descent...."
other interpretation :
No need to select engine anti ice on at top off descent or during descent until just "before" entering icing conditons. Even though well established in the descent you were not actually in icing conditons up until now (later on during the descent).
Does the "before" in the quote from the FCOM above mean :
- before commencing descent during which you will encounter icing conditons (not at the moment now but perhaps later on)
or
- just before entering icing conditons during descent
Descent in icing conditions ?
Does that mean if you are in icing conditons now and will be in continuous icing conditons for the whole descent or if just any (very momentarily) icing conditions expected on descent ?