I remember reading somewhere (may have been on pprune) that some airline called V1 a few kts early, as had been their custom. This continued until Airbus pointed out that their published V speeds already accounted for the human factors aspect of it, and thus calling V1 early was inadvisable. Again, not entirely sure of the source. It may have been an airbus publication, or just something that was posted on a forum, but it bears consideration.

Yes, you've still calculated the perf with the 1.15 or 1.3 margin for good reason.

For me, the V1 call doesn't mean "Decide now!" It means "Decision time is over - we're going!" (Absent, of course, an event that makes flight impossible).

I totally agree with Pattern

That is a very dangerous statement. IMHO, a wise pilot should never totally rely on the other pilot's speed call-out as a basis for such a critical decision as a high speed rejected takeoff. From observations in the simulator, it is rare that a high speed rejected take off on a limiting runway is conducted perfectly. In real life, that certainly is true. If there is a mistake on a limiting length runway, the chances of an over-run are high.

If a PM has not called V1 it could be for any number of reasons. That includes complacency or laziness, distraction (eg looking at an N1 reading which seems not quite right), fiddling with a thrust lever trying to get an exact N1 reading, and worst of all, momentary incapacitation. The decision to make a high speed rejected takeoff on a limiting runway length is probably the most critical life and death decision a pilot will make in his flying career. To base that decision on one man's verbal call-out rather than using your own eyes, is really stretching your luck.

There are some pilots, aware of the circumstances of previous accidents, that make the mental decision to go well below the calculated V1 even up to 15 knots below V1. They are playing the statistics i.e. the risks involved with a high speed abort versus the lesser chances of colliding with an obstacle during the lower flight path in the go situation. You have to be realistic here. The number of accidents that resulted from a high speed abort as against the number of accidents where trees and other obstacles were clipped during the second, third or fourth segment during IMC departures.

The 2 seconds acceleration after V1 certification was amended in the early 90s to be replaced with a distance equal to 2 seconds of travel at V1 speed. Not the same.

Indeed. However one needs to keep in mind that the acceleration was with the remaining operating engines, and the distance at the V1 speed. So the rundown characteristics need to be taken into consideration when considering "not the same". As the rationale was to inject a pad for those things which catch us out, the distance requirement is more readily comprehended.

Yes, you've still calculated the perf with the 1.15 or 1.3 margin for good reason.

I'm probably just having a slow day .. the factors relate to ?

Here's an interesting video that covers this. (fast forward to the 14th min of the video for the V1 part)

Do what your SOPs say, there might be a reason why they ask you to do it a certain way, In doubt, email your tech pilot and he should have the answer.

I was surprised on switching from the 737 to the airbus that the latter did not have automatic V1 calls. On the 737 the V1 call started at V1 -3 kts, but i have no idea if that was a company preset or boeing setting. With the usual 1 or 2 knot difference between V1 and Rotate there is the choice of either calling V1 a tad early, or Rotate a bit late. That said, i much prefer an automatic callout, the aircraft calls all other kind of stuff out, why not V1?

. . or that one of you has bugged the wrong speed :O

Absolutely nada in this case as reject at V1/Go is calculated using Gross not Net performance.