10. IRREGULAR OPERATIONS
10.1 Cold Fuel
As previously described, the actual specific freeze point derived by Airindia will be placed in the aircraft logbook prior to departure. The new operational limit becomes the temperature three degrees warmer than that measured freeze point value, not the default EICAS caution value of -37 C.
When operating in an area of SATs of -65 C or less, crews need to remain vigilant to ensure the minimum fuel operational limit is not exceeded. If the limit is approached, consider changing altitude, or changing routing. It generally is better to manage fuel temperature with altitude/SAT than Mach/TAT. Increasing Mach will raise TAT, but burn considerable fuel. Increasing your Mach from .84M to .85M will yield approximately a.7 to 1.0 increase in TAT. Careful altitude planning will save fuel. Routing changes can be difficult in Russian airspace. Changing altitude is generally a better solution. Consider that extremely cold air tends to pool in the Tropopause and that warmer air can sometimes be found at altitudes above the Tropopause.
If you are experiencing difficulty receiving your clearance for an altitude change, consider contacting Dispatch on SATCOM for assistance with Russian ATC. If all else fails, consider declaring an emergency.
Experience has shown that fuel tends to cool quickly and is very slow to warm.
Refer to the Flight Plan and Wind Summary to predict the area of forecast cold air. Take action before entering the cold air as once the fuel temperature drops, it will not rise for as much as two hours of continued exposure to warmer air. Once warmer air is reached, re-assess your fuel status.
10.2 Cold Temperature Altitude Corrections
During operations in extreme cold temperatures, the airplane is lower than the indicated altitude. For considerations during low altitude maneuvering and instrument approaches in cold weather, refer to cold temperature altimeter correction table in the Cold Weather Operations portion of the B777 Flight Manual, section 3, Normal Procedures. A cold weather Altimeter Correction table is placed at Appendix “A”.