Can anyone shed any light as to why the Eurocopter MMEL for the EC 120, which is a VFR only helicopter, (and perhaps several other aircraft) requires there to be a temperature of more than 4.5 degrees C AND no visible moisture as conditions for flight under the MEL if the Pitot Heater is inoperative?
For those operating in warmer climates it is unlikely that they will get anywhere near 4.5 degrees C whilst operating below 10,000 feet but if they can see rain cloud etc. it is a no go item. I would have thought from the comments above that providing you are above 4,5 degrees C you could fly quite happily in rain without any adverse effect on an unheated pitot head.
Before I start the battle to try and have the MMEL changed I would appreciate an insight, if anyone has one, as to why / how this condition / remark in the MMEL has evolved or been arrived at.