Originally Posted by
seagull967
All good, but still wondering about that 777 approach speed bump. Vmca is approximately 136-137 KIAS and so, so depending on flap settings you'll hit the floor at weights something below 460,000 pounds . But something else happens at the lighter weights that I cannot find. I show Vref go from 136 at 340,000 pounds to 143 at 339,000 pounds and below. I have yet to find a satisfactory explanation for this.
Which variant are you looking at? I have four in the QRH and they all have Vref decreasing with weight and pressure altitude. On one of them, at very light weights, Vref for F30, F25 and F20 are the same, indicating a Vmca floor.