Narrative:

While deviating around a quickly developing thunderstorm cell; speed was gradually slowing from mach 82 to 15 KTS above amber bar. The tat at FL410 was -26C before and after the event with a FMC maximum altitude of FL423. Downwind of the cell; the tat climbed to -6C with a corresponding maximum altitude of FL403. To maintain minimum speed a descent of 200-300 FPM was required. Concurrent with the performance degradation; the left eec went inoperative; slightly lowering the thrust limit to the left engine. At FL400 the aircraft began to climb back to FL410 at about 500 FPM. The excursion from clearance altitude lasted under five minutes. Our position during the altitude deviation was 20-30 miles east of the airway. There were no other aircraft on frequency or on our TCAS display. The radio had a lot of static; and continuous attempts were made to contact center. We were uncertain if they heard or understood us; but we continued to state our circumstance and intentions in the blind; even on 121.5. Once around the weather all conditions returned to normal; communications were regained; and the flight continued normally. No declarations or reports to ATC were made and none were requested. Both the first officer's radio and the eec were entered into the maintenance log for repair.

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Original NASA ASRS Text

Title: A B777 deviated from their assigned route because of weather at FL410 in foreign airspace; unable to contact ATC. During the deviation a 20 degree temperature rise resulted in an airspeed loss and a requirement to descend for airspeed control.

Narrative: While deviating around a quickly developing thunderstorm cell; speed was gradually slowing from mach 82 to 15 KTS above amber bar. The TAT at FL410 was -26C before and after the event with a FMC maximum altitude of FL423. Downwind of the cell; the TAT climbed to -6C with a corresponding maximum altitude of FL403. To maintain minimum speed a descent of 200-300 FPM was required. Concurrent with the performance degradation; the left EEC went inoperative; slightly lowering the thrust limit to the left engine. At FL400 the aircraft began to climb back to FL410 at about 500 FPM. The excursion from clearance altitude lasted under five minutes. Our position during the altitude deviation was 20-30 miles east of the airway. There were no other aircraft on frequency or on our TCAS display. The radio had a lot of static; and continuous attempts were made to contact Center. We were uncertain if they heard or understood us; but we continued to state our circumstance and intentions in the blind; even on 121.5. Once around the weather all conditions returned to normal; communications were regained; and the flight continued normally. No declarations or reports to ATC were made and none were requested. Both the First Officer's radio and the EEC were entered into the Maintenance Log for repair.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.