B737-700
Flight Crew Last 90 Days 129
Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Aircraft; Weather
During enroute cruise at FL400 and flight planned Mach; the Number 2 engine rolled back to approximately 60% N1. The rollback was rough; like a cough; and was noticeable through both N1 gauge indication and aircraft feel. During the rollback; the autothrottles disengaged. As PF; I slightly reduce power on Number 2 as the engine stabilized and started to recover to normal power. No malfunction indicators or messages were received. The engine operated normally for the remainder of the flight. The SAT was approximately -58 degrees and the anti-ice was off. At the time we were deviating around radar returns for weather; but were not in any rain; turbulence; or dense clouds. We couldn't really tell the thickness of the weather because it was still dark. Shortly before the event; I had turned on the wing lights to check for icing and the wings were clear. Suggest investigation of potential high altitude; low temperature (below -40 SAT) engine icing.
B737-700 First Officer experiences an engine rollback at FL400 to 60% N1; then a slow recovery. High altitude low temperature internal engine icing is suspected.