Re: S80 Ground Checks

From:         gsmoff@Mcs.Net (gary)
Organization: MCSNet Internet Services
Date:         09 Apr 96 14:22:49 
References:   1
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In article <airliners.1996.454@ohare.Chicago.COM>, (Mark Misener) wrote:

> Last week I was on an American Airlines S80 Chicago to San Diego (and
> return). I noticed that the ground crew were putting up ladders against
> the leading edge of the wing near the wing-root, and were running some
> kind of plastic brush, or something back and forth (from lead edge to
> trail edge). I couldn't see exactly what they were doing from where I was
> sitting, but, I've been on plenty of flights, and I don't recall seeing
> anyhting like it before. On top of that, I was talking to a friend of
> mine, and he said that he was also on an S80 recently, and observed the
> same thing. He also mentioned that he noticed a parked S80 with the skins
> removed at the wing-roots. Does anyone know what was going on?

I sure do, the cold fuel in the center tanks of the MD-80 is prone to
cause what is called "clear ice" to form at the wing roots. This icing is
apparently pecular to MD-80's for some reason.  Aside from the obvious
hazards of icing (extra wieght and disruption to airflow) this clear ice
is likely to break off the wing at rotation due to the flexing of the
wing.  For an aircraft with tail mounted engines whose inlet are directly
in line with the icing, this event can often be fatal.  American Airlines
has black anti-skid paint applied to the wing in the areas prone to
icing.  The theory is that if clear ice is present a man scratching the
wing in that area with a simple plastic pole will be not be able to feel
the rough texture of anti-skid paint, thus confirming the presence of
clear ice.  American also has an electrically heated blanket applied to
the wing skins in the area clear ice forms,  I'm sure your friend happened
to see a plane  in the process of having that blanket changed.  The wing
skin itself consists of several "planks" running from root to tip parallel
to the spars, these planks are for all intent and purposes none removable
in the field.

Gary S. Moffitt