Description

On 20 December 2009, a McDonnell Douglas MD-83 (F-GMLU) being operated by Blue Line on a positioning flight from Paris CDG to Kuwait with six crew on board requested a climb to FL 370 which was approved. Soon after levelling in day Visual Meteorological Conditions (VMC), aerodynamic buffeting began and, having realised that the speed was low, the crew initiated a descent to FL 350 during which the buffeting ceased. The remainder of the flight was uneventful.

Investigation

An Investigation was carried out by the French Bureau d'Enquêtes et d'Analyses (BEA). Flight Data Recorder (FDR) data was successfully recovered to assist the Investigation.

It was established that during pre-flight preparations, the First Officer, designated as PF, had mistakenly entered the aircraft ZFW of 86,520 lbs into the Performance Management System PMS) in place of the GWT (Gross Weight) of 129,673 lbs. Since the PMS requires that the GWT value should be between 88,000lbs and 170,000lbs, the entry led to the annunciation of the CHECK GWT message. The First Officer stated that “he then re-entered the weight value and the error message disappeared” but that he did not remember what value was entered. It was confirmed that the aircraft commander had not cross-checked the weights entered.

It was noted that prior to departure, the FPL had shown a cruise level of FL 350 based on a GWT which was 5000 lbs below the actual GWT and considered that “the crew might have been alerted when the PMS proposed a cruising level higher than FL 350 (FL 370) even though the aircraft was heavier”.