Flyer 719,
Does the length of the runway affect V1 descision?
Up to a point, YES, and after that point, NO.
Any Takeoff is limited to the least of Accelerate-Stop Limit, Brake Energy limit, Takeoff Distance Limit, WAT Limit, and Obstacle Clearance Limit. With all else being equal, Takeoff on a very short runway will be Accelerate-Stop limited (and/or Accelerate-Go limited if using a balanced field technique). The V1 in this case obviously is governed by Accelerate-Stop, whilst WAT and Obstacle limits are not a problem.
Now, progressively increase the runway length, Accelerate-Stop limit increases, whilst Obstacle limited weight decreases due to increased gradient required because of a shorter distance to the obstacle. Continue this runway lengthening process process up to the point where Accelerate-Stop limit equals the Obstacle limit, and the takeoff weight has been optimised. Up to this point, any rejected takeoff must be accomplished prior to V1. Any further increase in runway length is a bonus, if we used it, Accelerate-Stop limit will certainly increase, but the Obstacle limit will decrease, so, we don't use any more runway in our calculations than that necessary for Accelerate-Stop (or Balanced Field).
Thus, if we have 'excess' runway available, the aircraft could be stopped from a speed above V1, but such action is
EXTREMELY inadvisable, except in a
DIRE emergency.
Engine failures, tyre failures, doors opening etc. are not dire emergencies, and the mathematics of the situation allied with statistics, strongly advocate
GO as the only option. If, on the other hand, the aircraft is judged as INCAPABLE OF FLIGHT, as would occur with a complete control jam, or control failure, then a
STOP from a speed above V1 may be the only option, accepting that an over-run at 40 to 50 knots is infinitely preferrable to an uncontrolled ground impact from in-flight.
I speak from experience, it
HAS happened to me. Fortunately, on the day, the aircraft required 2000 M of runway, but had 3500 M available. The aircraft was later proven to be incapable of controlled flight, if I had managed to somehow get it airborne, I would not be here now to make this assault on your senses.
Fly Safe, think outside the box,
Old Smokey