cold soaked?
http://www.patentstorm.us/patents/71...scription.html
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The physics behind the frosting phenomenon is well known. After a certain length of flight time at cruising altitudes, wing tank fuel temperature can reach -40 degrees F. When the wing fuel reaches such low temperatures it is commonly referred to as "cold soaked". For reasons of aerodynamic stability, relatively warm "belly" fuel on an aircraft is typically burned first. This often leaves the "cold soaked" fuel undisturbed in the wings during short duration flights. This "cold soaked" fuel, when remaining in contact with the wing surface, can result in non-environmental frosting upon landing. This is particularly problematic, if a particular airline route or schedule of flights should involve a number of short hops to pick up addition passengers or cargo. Often these stops are required to be of short duration for economic reasons. The non-environmental frosting can prevent an aircraft from maintaining a quick turnabout on these short hops and may cut into the benefits or gains that may otherwise be realized.
The desire for a quick turnabout from landing to takeoff can conflict with the necessities of dealing with such non-environmental frosting occurring after landing. Although an airline may allot only fifteen or twenty minutes for a given stop, a heavy coat of frost and ice may rapidly form on the top surface of the wings after only five or ten minutes on the ground. FAA regulations may then require the captain of the airplane to either wait for ambient airport weather conditions to eliminate the frost and ice formations or actively have the wings de-iced. Each of these solutions requires a penalty of time and money to implement. Many de-icing procedures can carry with them environmental concerns as well. Therefore, current approaches towards the removal of non-environmental icing often are not compatible with the airline industries goals involving scheduling, cost savings, and time management.
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Sad someone died. Looking at the pictures, seems a miracle anyone survived that.