Although time to v1 looks suitable, it is not!!
It would be if there was a thrust problem. For a weight problem however, you are calculating time to a WRONG v1, with a WRONG thrust. On a short runway, I will not have any indication that I can still stop the aircraft after the WRONG time to the WRONG v1 if I suddenly weigh x tons MORE...
So it is the old saying... BS in, BS out.. and that goes for time to v1 as well...
I'm not convinced. If the weight entered is too low, it IS essentially a thrust problem.
(Making numbers up) If your V1 is 120 kt and you need 1000m to stop from V1, if you haven't reached 120kt by the calculated time you know:
- you are slower than 120kt and
- you have more than 1000m to stop.
The wrong time and wrong v1 only cause a problem if the extra weight has more effect on braking distance than it does on acceleration distance. This is possible, but it doesn't sound likely to me.
Time to V1 catches the error where your weight is too high and the thrust is too low - and the errors accumulate to provide extra margin.