The investigation has determined that the pre-flight take-off performance calculations were based on an incorrect take-off weight that was inadvertently entered into the take-off performance software on a laptop computer used by the flight crew. Subsequent crosschecks did not detect the incorrect entry and its effect on performance planning.
As a result of this accident, the aircraft operator has undertaken a number of procedural, training and technical initiatives across its fleet and operations with a view to minimising the risk of a recurrence. In addition, the aircraft manufacturer has released a modified version of its performance-planning tool and is developing a software package that automatically checks the consistency of the flight data being entered into the aircraft's flight computers by flight crews.
The investigation has found a number of similar take-off performance-related incidents and accidents around the world…….
The investigation is continuing.

The flight crew’s work and sleep history was entered into the Fatigue Avoidance Scheduling Tool (FAST)15 that was originally developed for the US Air Force. The FAST software predicts effective performance using calculations developed from empirical research findings of studies into the effects that wakefulness and circadian rhythms have on cognitive performance. These calculations take into account both work and sleep patterns as well as the quality of sleep.

The output from FAST focuses on establishing an individual’s ‘task effectiveness score’. Both crew members had a score that was near the top of the effectiveness range.

The operator supplied the results from another commercially available fatigue
modelling tool that was used as part of their FRMS. That model used work hours and sleep/wake data to determine an ‘alertness prediction’, and was developed from data collected in laboratory studies and on long-haul flights. Those results correlated with the FAST assessment.

The examination of flight and duty times and fatigue is continuing.