To all, please take this not as a criticism of the crew and/or airline involved. Time will be the only teller of the full and true story. However, history of such incidents point to a weight and balance/speed cards/FMC speed programming issue. Which leads me to….
All airlines teach procedures…..few teach techniques, techniques to confirm procedures are adhered to. We have all in our careers seen another pilot do something and say/think “that’s a good idea – I think I’ll do that”.
I submit the following as a technique to perhaps catch the above mentioned problem (I have heard that at some carriers this may be procedure).
Most airlines have estimated weights included in the flight planning paperwork. In fact, for fuel burns to be realistic, particularly on long haul flights, estimated weights better be close to actuals, or a last minute trip by the fuel truck will be involved. My suggestion is that there is a takeoff number that is (almost) strictly a function of weight, and that is the “outer bug” at most carriers, clean maneuver speed (there can be an argument here for V2, but that can vary with different TO flap settings, so V clean maneuver I think is best). Set (or write down) clean maneuver speed during cockpit setup and if the final numbers are significantly different, investigate why. This will normally catch the “big errors” (there have been lots of 100,000 lb. errors in large aircraft tail scrape/tailskid events). And this may catch an error in the landing numbers also…..leave the outer bug set at it’s takeoff value – when setting bugs for landing, the only variable here is fuel burn off. Come up with a quick and dirty formula for the reduction of clean maneuver (I use 3-4 K per hour of flight). If there is a big difference, investigate.
Not trying to be a smart ass here…..there for the grace of God……….But I fly backside of the clock mostly, and try to create as many techniques/tools to keep the blue side up….fatigue induced errors are often so insidious.