I have been following the very interesting Iberia
IB6166 BOS-MAD thread and it has prompted a SLF de-icing question.
A couple of winters back I was on a TOM 737 flight from BOH to CDG. It was middle of the day no frost and about +3c. While we were boarding it started raining. After boarding the capt announced there would be a 'short delay for de-icing', which was a bit of a surprise. The Ryanair next to us departed without de-icing.
As the sector from BOH-CDG is short it may be that the a/c didn't require fuel (at ambient) and as TRT was short from the previous arrival would the decision to de-ice in positive ambient temperatures and rain be based on the potential below 0c fuel temperature in the wing from the previous flight causing freezing on contact? If so how does the PIC make this judgement call as I assume it takes a long time for fuel temps to normalise to ambient field level temps that are only a few degrees above freezing?