I lived in Stockholm in early 1990s and travelled on SAS extensively.Excellent service too all over Europe and the MD 80 a lovely plane as pax.
Anyway to get to your point SAS had a very serious accident due to the fuel phenomenum described when an MD 80 routing ARN-CPH crashed about 4 mins after take off when undetected ice on wings cracked and detached(I think on Flap retraction ). As befanguy says this area is just outide the fuselage on the inboard wing and of course the ice went straight into both engines trashing them.
A very skillful crash landing was made resulting in no fatalaities from a seemingly calamitous situation of finding themselves with no power and 300ft cloudbase . I think the plane was at about 2000ft at time the engines packed up. It was not especially cold-oscilating around zero but it was very damp that morning and I am sure perfect conditions for the supercooled fuel to ice up the wing over the tanks.
After that SAS became very concious of the problem and I think put little tufted coloured strings on the wing that the ground engineer could waggle around to check no ice present. I imagine its very hard to actually see ice on a ramp in the dark and in the Scandi winter when the ice forms its pretty well dark all the time hence the need for more than a visual check
PN