Nuepielot
Welcome to the world of winter ops!!
In general terms you should not take off with any contamination on the wings (*) you may have hoar frost on the underneath, but no more than 3mm, JammedStab is correct that on the 737NG *some operators have a black boxed area above the wing tank within which cold soaked fuel surface frost is acceptable for departure.
A degree of common sense and to be honest experience is required when operating in hostile winter environments and you may well go several years in the UK without de-icing depending on how your roster falls, meanwhile Northern Norway/Sweden/Finland i have had to de-ice on every sector often several days running, i would say if in doubt, de ice, but equally i have seen airlines de ice a wide body aircraft on turn around because of a few flakes of dry snow, its expensive to de ice, but crashing more so!! remember the de ice fluid charge normally funds the equipment, staff and post clean up & treatment so around €10-€15 per litre is the norm 200 -1500 litres is often used on a narrow body a de ice it is a big cost. This cost also depends on the type of fluid used of course.
At AMS i once saw what i call the sheep effect, where one crew requested de icing and shortly afterwards other crews were doing the same, but not all aircraft are the same.
I remember doing a walk around on an early morning departure out of LHR my aircraft type was a low wing regional jet and had frost on the upper wing surface, the line engineer had checked the airbus on the next stand which had been there all night and was clean, yet our low wing aircraft had frost!!
A good tip is to look at the cars in the car park that have been there overnight or the tops of ramp vehicles these are often a different colour to the mainly silver wing tops and its easier to see frost against a colour, hence the black boxed area referred to above on the NG.
Settled snow is a no go, you can't see whats underneath it, but search Youtube Russian airbus take off with snow covered wings !!!
Enjoy your winter flying
Last edited by LNIDA; 11th November 2014 at 14:26.
Reason: correction