The minimum fuel temperature operational limit is based on its specification freeze point. It is worth noting that the freeze point of a fuel is the point at which the last wax crystal melts in a frozen sample. This value is approximately two degrees warmer that the point at which the first wax crystal forms as the fuel is cooled. For Jet A, the specification freeze point is -40C. A 3 C operational margin is provided, yielding an operational limit of -37 C. The first wax crystal would form at -42 C, so a margin of five degrees is provided.
Issue I 28.08.2007 Rev. 0
FLIGHT DECK PREPARATION
All flight deck preparation will be similar to normal flights except that the pilots will pay special attention to checking the CFP ,the ATC clearance and the filed flight plan for accuracy, FTP, True Tracks, etc.
6.1 Polar Exposure Suits
The cold weather exposure suits are stored in the compartment above door 1R. There is an internal sealed compartment. During preflight it will be necessary to inspect the compartment seat for integrity, and if the seal has been broken inspection by maintenance is required.
The purpose of the suits is to allow crewmembers designated by the captain to exit the airplane to coordinate ground operations or preflight during extreme weather conditions.
The suits are required aircraft equipment in order to fly Polar operations.
6.2 Fuel Temperature Operational Limit
An approved alternate method for determining the minimum fuel temperature operational limit is to apply the 3 C operational margin to the known freezing point of the fuel loaded on the aircraft.
There are two methods by which the fuel freeze analysis can be conducted depending upon OAT and time considerations. It the OAT is below 32 F, use of the fuel tank drains and drip sticks are prohibited due to the possibility of ice and moisture preventing the closure of the drain/stick. In this case, prior to refueling, any remaining wing fuel on board the aircraft will be transferred into the center tank (leaving approximately 2500 lb. in each tank for the APU and hydraulic cooling). Samples of the fuel will be taken from the fuel hydrant and analyzed. In this way, the freeze temperature of the wing fuel (which is always colder than the center tank) can be determined without attempting to sample the mixed fuel within the wings (onboard fuel could be Jet A or Jet A-1). The analysis can also be conducted by taking samples from the aircraft wings after the new fuel is loaded and mixed with the onboard fuel. Either method will analyze multiple samples and the most conservative (highest freeze temperature) will be recorded by the analyzer.
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