The 77L in its freight version has some very special characteristics that make any 'gut feeling' or 'V-speed vs. weight dead reckoning' difficult.
As it is equipped with the 110lbs GE90 engines but the short body and a very light DOW, the Vmc on ground and in the air is extremely delicate. Imagine an empty flight TOW (145 tons absolutely possible vs. max TOW 347t) one can imagine what an engine failure and subsequent max power on one of these power plants means aerodynamically.
Therefore the Vmin's for such take-offs and landings requires speeds in excess of up to 20kts more than what the weight might normally dictate. The same effect happens with the assumed temperature, which remains fairly low in such cases.
This is not to excuse the crew, but it makes error detection with techniques mentioned in many contributions above quite tricky.
Cross qualified flying with animals so different in weight and characteristics, as well as a huge spread of cockpit equipment will always lead to errors. The Airbus 32/33/34 family has a long history and now the T7 family joins with ever more versions of airframes, engines and cockpit equipment. The trapping of errors is that much more demanding. Including more calls or time checks during take-off, or a quadruple crosschecking during calculations only increase workload and shed the initial shortcomings like short cuts in training, lack of basic experience and most urgently fatiguing rosters.
Last edited by glofish; 8th Jun 2015 at 15:16.