Working from the speeds in the cited article:
- 240 kmh = 130 kt
- 055 kmh = 030 kt
- i.e desired speed = 160 kt
The plane's damaged flight data recorder was recovered last week. Fowler has said it indicated the 747's four engines were functionally normally.
Once, I could do the calculations to work out the fraction over MTOW that would produce that reduced speed. However I suspect that the speed given out by TSB is the maximum achieved just before collision with the berm instead of the normal rotation point which could indicate that MTOW was exceeded by a substantial fraction.
A night takeoff deprives you of early visual clues that acceleration is not quite what's needed -- perhaps until you're getting too close and personal with the end of the runway.
There has been discussion before that it may be useful to work out distance or time to V1 and abort if V1 is not achieved by that point or time.