Thomson Airways flight BY-1526

A Sunwing Boeing 737 NG underperformed at takeoff on July 21, 2017, from Belfast International Airport, due to an incorrectly entered Outside Air Temperature (OAT). The engines operated at 81.5% speed, rather than 92.7% as required, giving 60% thrust. There were 185 people aboard. The area beyond the runway and the terrain beyond were largely unobstructed, and the aircraft eventually climbed away undamaged. The remainder of the flight, to Corfu, was uneventful. The "serious incident" at take-off was recognised and reported when airport staff subsequently observed minor ground damage. The incident was due to a data-entry error by aircrew, into the flight management computer, and the investigation Report concluded that the crew could not reasonably have been expected to recognise the anomalously low speed sooner or intervene more effectively. The incident was reported in industry and enthusiast sources, (identified in one as "significant" The Report listed several examples of aircraft underperformance at takeoff, reviewed the history of relevant industry efforts, and recommended that a Takeoff Acceleration Monitoring System and associated certification standards should be developed without further delay.
The outside air temperature was 16°C, but the operating crew entered incorrect figures (variously -47°C and -52°C) for the airport outside air temperature, into the flight management computer, resulting in miscalculation of the required , the engine fan speed (low-pressure compressor speed) required on the take-off run.
Neither the installed flight management computer software nor the in use helped in detecting the data input error. A recent software release had not yet been installed, and the software omitted the cross-check of the pilot input data against the outside air temperature actually measured. The pilot became aware of the aircraft’s underperformance late in the take-off run but did not intervene effectively. The Report explored various human-factors aspects of the incident, concluding that the pilots could not reasonably have been expected to respond more quickly to the developing situation, either before or after becoming airborne. It reviews and lists recent incidents of aircraft underperformance at take-off, reviews industry efforts to provide automatic warning in such situations, and calls for closer regulatory attention to pilots' portable computers ('electronic flight bags').
* Takeoff Performance Monitoring System (TOPMS) or Takeoff Acceleration Monitoring System (TAMS)<ref name=":0" />

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