Winter Ops De Ice

[Neupielot]

Hi guys,

Never de-iced before.

Assuming the aircraft is clean, no contamination and no sub-zero temp fuel, is it a requirement to de ice/anti ice if the ground surface condition is such that the OAT is below 10 (6 or 7 degrees) and its raining? No snow or ice on ground surface. Just rain/drizzle.:O

Many thanks.

[esreverlluf]

No, not at my company, however there are significant variations between companies!

[BOAC]

OAT +10 is mainly relevant to engine icing, not airframe.

[JammedStab]

Actually, the OAT is irrelevant. What is relevant is whether or not there is frozen contamination adhering to the critical surfaces. And if there is, is it allowed for takeoff. Typically, airliners can have certain amounts of frost on the bottom of the wing. At least one 737NG airline can have frost in certain areas on the upper surface of the wing. The first case has to do with cold fuel causing frost to form, frequently at an OAT above freezing.

So in the case of the original question, it is possible on some aircraft to have rain/drizzle freeze on top of a wing where it is affected by cold fuel. Some aircraft such as the MD-80 are more vulnerable to this than others.

So what to do. A visual check can help but clear ice can be difficult to detect, especially on a wet wing. Trained maintenance is the best answer for actually getting a tactile check. A pilot may be able to as well but it could be at risk of some sort of falling injury due to lack of proper equipment.

Knowledge and experience on type is useful for deciding how likely this is and when to check and how vulnerable your aircraft is to damage from pieces of ice if you do takeoff without a proper check.

Aside from that, there is little other risk in terms of critical surface contamination at the OAT originally mentioned.

As an aside, watch out for freezing fog causing ice buildup on propellers.

[LNIDA]

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

[Winnerhofer]

Individual Membership Application | Flight Safety Foundation (http://flightsafety.org/aerosafety-world-magazine/november-2014/hot-intelligence)

[ManaAdaSystem]

The answer to the first posters question is no.