framer
You said : Here is how I imagine it working; if for example you put the data into the laptop and it came out and said max time to 100kts is 35 seconds. You then trundle out to the runway and roll, at 35secs you notice you are only at 98kts, either abort or TOGA and off you go, if you get to 35secs and you are at 85 kts...abort.
Which is exactly the point I was trying to make. If you do it this way it works - if you measure the time to 100 kts and discover it's actually 45 seconds not 35, what the heck do you do next? Can you be sure you have enough tarmac to stop?
It strikes me that if more departures are going to be made at reduced power using a bigger percentage of the available tarmac for economic resaons, then it's becoming essential to check the progress of the roll, other wise we're going to see more events like EK407.