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B737-800 flight crew experiences a rapid temperature increase of 21 degrees at FL380 causing a buffet alert and thrust reduction. Thrust is manually controlled to maintain mach .78 and a few minutes the temperature returns to its' previous indication. After a couple of minutes the temperature increases again and the crew requests to descend to FL340 for the remainder of the flight.
| Attributes | |
| ACN | 953636 |
| Time | |
| Date | 201106 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZMA.ARTCC |
| State Reference | FL |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Flight Dynamics |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Person 2 | |
| Function | Captain Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Inflight Event / Encounter Weather / Turbulence |
Narrative:
At FL380 approximately 20 east southeast of forkk; the isa temperature on the FMS increased from +7 isa to +28 degrees. This triggered a 'buffer alert' on the FMC screen. The FMC then tried to slow the speed. We intervened and disconnected the auto throttles and managed the speed. On the VNAV cruise page the max altitude dropped from 39;700 ft to 37;100 ft. We were deviating to the east for a storm. Our ride was smooth throughout with ripples of chop. We also turned on the anti ice as the sat had now changed from -51 degrees to -28 degrees and we were IMC. While [we were] staring at the FMC all temperatures returned to normal. We re-engaged the auto throttles and observed all inputs. A few minutes later it happened again. The captain requested lower and we descended to FL340. The captain made a report to ATC to pass on to traffic in the vicinity and sent dispatch a detailed message. Flight continued safely to destination.
Original NASA ASRS Text
Title: B737-800 flight crew experiences a rapid temperature increase of 21 degrees at FL380 causing a buffet alert and thrust reduction. Thrust is manually controlled to maintain Mach .78 and a few minutes the temperature returns to its' previous indication. After a couple of minutes the temperature increases again and the crew requests to descend to FL340 for the remainder of the flight.
Narrative: At FL380 approximately 20 east southeast of FORKK; the ISA temperature on the FMS increased from +7 ISA to +28 degrees. This triggered a 'Buffer Alert' on the FMC screen. The FMC then tried to slow the speed. We intervened and disconnected the auto throttles and managed the speed. On the VNAV cruise page the max altitude dropped from 39;700 FT to 37;100 FT. We were deviating to the east for a storm. Our ride was smooth throughout with ripples of chop. We also turned on the anti ice as the SAT had now changed from -51 degrees to -28 degrees and we were IMC. While [we were] staring at the FMC all temperatures returned to normal. We re-engaged the auto throttles and observed all inputs. A few minutes later it happened again. The Captain requested lower and we descended to FL340. The Captain made a report to ATC to pass on to traffic in the vicinity and sent Dispatch a detailed message. Flight continued safely to destination.
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.