Originally Posted by
FlyingStone
If there wasn't freezing fog (so fog and temperature 0C or less), or any kind of precipitation, I don't think it should be a problem, especially with wing surface (fuel tank) temperature above OAT/DP, which means you aren't even in active frost conditions anymore.
That being said, if you're not 100% sure, the easiest way to solve the problem is to de/anti-ice again. Remember, at the end of the day HOT tables are just guidance, nothing more than that.
Yes, the active frost conditions had been superseded by new environmental conditions. As you say, the warm fuel uplift had increased the wing surface temperature. The new conditions were fog and LVPs.
it was not Freezing Fog which in my company is defined as 0 degrees C and <1000m visibility. It was, however, Freezing Conditions which my manuals define as temperatures of 3 degrees C or below and precipitation or standing water.
I looked at the relevant Type II HOT table yesterday and wondered whether the Freezing Fog HOT could have been used. Though technically not Freezing Fog because OAT was above 0 degrees C, it was fog in Freezing Conditions as defined by my company. The longest HOT for the Freezing Fog HOT would have covered us and would surely have been a conservative calculation?
Thanks for all the suggestions. I’ve always leaned to the conservative side when it comes to de-icing and will continue to do so, following the mantra: if in doubt, de-ice and the clean wing policy. My company puts safety first when it comes to de-icing and fuel policy so there’s no pressure to take risks.
Happy New Year all.