MD80 series

[matblack]

Everytime I fly SAS from CPH they seem to have a special ladder that goes over the wing. Before push back a ground worker seems to climb up and look at something. It happended each time after deicing in Winter and so I thought he was just double checking the ice was clear. However, they still seem to do it in warm weather. What are they doing ?

[bafanguy]

matt,

They are, indeed, checking for ice following deicing. However, a peculiarity of the MD80 series is the tendency to form ice on the top of the wings in high humidity conditions up to 10/15C due to the configuration of the fuel tanks. If there is cold fuel in the center tank ( which extends 5 feet outboard of the fuselage on each wing ) in contact with the upper surface, the upper wing may get cold enough in this area to cause ice to form in high humidity conditions.

Some carriers have installed electric heater blankets that operate on the ground to prevent this happening. The blankets, however, are not used ( turned off ) during environmental icing like snow, frost, etc., as they allow ice to melt , run back, and refreeze causing other problems. Absent the heater blankets, the visual inspection is still required when the temp/humidity conditions are favorable to ice formation.

And, the inspection by ground crew is still required after deicing to verify the effectiveness of the procedure.

[pax britanica]

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

[used2flyboeing]

HENCE - the MD80 is no longer a certifiable design because of not only ice injestion, but also because of blade out which was demonstrated recently in a fatal uncontained engine burst which took out a row of passengers and also the adjacent engine on the other side of the galley ! You will never see another one of these configurations unless the engines are staggered ( the RUssians have patented this configuration - no one will pay them royalties ) .. even Bomb has indicated that there new RJ will be a wing mounted engine design - abandoning the CRJ200/700/900 config. Makes sense as well from structural efficiency standpoint as well .. IE no need to make 10 meters of systems runs from service centers located in front of airplane ( wing root & EE bay ) to tail ..

[747FOCAL]

OKAY....I was just back from the bar when I wrote that last one. Please forgive me......:E

[bafanguy]

U2FB,

By "..no longer a certifiable design..." do you mean the FAA would not allow another airplane to be built with after-fuselage mounted engines, or do you mean this configuration is not too practical for operational reasons, ie ice, throwing a blade ?

As for the blade incident, it was, in fact, an MD88 if you're talking about the KPNS takeoff where the woman and her child were killed.

I flew the MD88 at Delta until I retired. The failure was traced back to some flaw in the milling process if I remember correctly.

All airplanes have some design features that require "working around" one way or another. The wing ice has been successfully handled ( for the most part ) by heater blankets, improved operating procedures, and an increased awareness of the problem. Can the problem still happen ? Yes, the same way any other airplane's quirks can jump up and bite you if you're not careful.

[used2flyboeing]

pax britanica - I used to fly those SAS MD-80s with all the locals on them around the northern European countries - all I remember is trying to keep my head below the cigarette strata in the cabin - cough - cough !

Any airplane configurator will tell you that the MD80 config will not be built again because of uncontained engine burst issues. Further, it is not an efficient configuration b/c all the systems run the length of the airplane - rather than keeping propulsion, systems and fuel in the same location - the modern twinjet config with engine under & forward of the wing result in a lighter configuration - that is easier to weight & balance - IE OEW center of lift ..

That being said - many many products are in commerce that could not be certified today - for instance a 1969 chevy w/o seat belts - or a lawnmower w/o a blade brake ..