The available Cross Crew Qualification and Mixed Fleet Flying guidance did not address how flight crew might form an expectation, or conduct a ‘reasonableness' check, of the speed/weight relationship for their aircraft during takeoff.
The problem experienced by the flight crew in determining the ‘reasonableness’ of the take-off performance figures that were calculated by the electronic flight bag is not unique to this accident. Previous investigations into similar data entry error and tailstrike occurrences have highlighted the inability of flight crew to conduct a ‘rule of thumb’ or reasonableness check of their take-off speeds.
Furthermore, an unintended consequence of mixed fleet flying appears to be a reduction in a flight crew’s ability to build a model in long-term memory to facilitate recognition of ‘orders of magnitude’ or ‘rules of thumb’ in respect of take-off performance data. That is, the effect of mixed fleet flying appears to exacerbate the difficulty already being experienced by crews in discerning the appropriateness of their aircraft’s performance.
Indeed, because performance figures that are quite reasonable for one variant may not be reasonable for another variant, affected flight crew would need to build a model for each aircraft variant experienced. Currently, there is no specific guidance to assist flight crew to form those mental models in respect of the weight and corresponding take-off performance parameters for a particular aircraft variant.