He was saying "Fuel Temp Low", its most likely a caution message. Jet fuel cannot be run through the engine if it is cold, as ice crystals form in the fuel filter and will clog it. Most jet engines run the fuel through the oil system to warm the fuel before filtering it. It also must stay above a certain temperature in the fuel tanks. The tanks are not heated, so the only way to warm them is to go fast and/or descend to warmer air. He was at 10600 Meters and descended to 7800 Meters, due to the bulk fuel temp was -40C. On the CRJ, we must keep the tanks above -30C and the engine fuel temp must be at least 5C. 99.5% of the time, this is not a problem as we are not at altitude long enough for the fuel to cool to -30. But this UPS MD-11 may have been up for 12+ hours, which would give the fuel plenty of time to cool.
Hopefully this answers your question. Any other questions, let me know.
