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Landing with Ice

A question for commercial pilots but I was interested to hear that the aircraft had landed with ice on the wings and then couldnt depart until it had melted. There was no visible moisture in the descent, which I guess is why bleed air might not have been used, but is it usual to use bleed air in the descent regardless and given that the wings cant be seen from the cockpit how do you monitor for ice accumulation.

It is quite normal that ice forms on cold soaked wings (due to low outside temperature at high altitude) by condensation of moisture in the air. But this often only happens after landing. Bleed air does not help much because it only protects the leading edges which are “warmed up” by the air during descent anyway. The ice forms behind the leading edges in the area of the tanks with their content of cold fuel.

EDDS - Stuttgart

what_next – yes that makes very good sense. What surprised me is the aircraft was not ready for turn around because the ice hadnt melted and the airport had no de-icing facilities. Of course you are right the cold soaking meant the fuel was very cold. Operationally it seems to me this could be a significant issue especially for landing after dark where even though the air temperature is well above freezing the ice takes a long time to melt.

https://en.wikipedia.org/wiki/Scandinavian_Airlines_Flight_751

That kind of ice can be difficult to detect without actually touching the wing.

huv
EKRK, Denmark

Fuji_Abound wrote:

what_next – yes that makes very good sense. What surprised me is the aircraft was not ready for turn around because the ice hadnt melted and the airport had no de-icing facilities. Of course you are right the cold soaking meant the fuel was very cold. Operationally it seems to me this could be a significant issue especially for landing after dark where even though the air temperature is well above freezing the ice takes a long time to melt.

Actually in my experience when the air temp is above zero it is not too much of a problem with that sort of frost. It is when it is at or just below AND you have cold soaked fuel, clearing frost can be a real pain as it tends to reform.

The worst is frost which has melted and then refrozen into proper ice.

Last Edited by JasonC at 27 Feb 17:23
EGTK Oxford

The other thing that can help is with a flight going for example from the UK down to the Canaries, even if landing after sunset or the temperature isn’t all that high, by the time you put on another 10000kgs of fuel or so to come back, that warming fuel will dilute the cold fuel still in the wing and help melt off the ice. On some aircraft (737-800 is one) the wing is susceptible to this cold soaked fuel frost (also called non-environmental icing) and as such many operators will place a limit on the amount of fuel to land with, in the case of the 738 this was often something like 6000kgs in summer months and 4000kgs in winter months.

United Kingdom
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