Originally Posted by
MalteseJambo
Bristol notes Performance 3.14 definition
'v1 means the maximum speed in the take off at which the pilot must take the first action (e.g. apply brakes) to stop the aeroplane.
Interesting - especially as the first action taken to stop the aeroplane is to retard the thrust/power/throttle levers. There's no point hitting the brakes against the take off thrust of the the remaining 3 RB211s on your 747-400!
V1 is a decision speed and is the highest speed at which you may take the decision to abandon the take off, and then initiate an immediate rejected take off procedure. The "2 seconds" is a bit of a red herring as any additional time/distance allowed above V1 is a buffer that allows for the time that it takes for the nerve signal to run from your brain, down your arm and retard the thrust levers. A simultaneous and similar signal should be running down your legs to initiate braking (that may not be all that is running down your legs, of course!).
I think I'm right in saying that the FAA and CAA/JAA had slightly different ways of calculating reaction time but that notwithstanding that, the decision is made at V1 and the actions are taken as quickly as humanly possible after that.
I've only ever had to do one RTO on a large jet but I am absolutely certain that my reaction time was well inside 2 seconds, but then I always assume/expect the worst and hope to be ready for it.