Bonjour Philippe
PV>V1 speed may be choose between V1 mini and V1 maxi; and each airline
PV>choose high or low V1 for an airplane type. And, on a runway, if you
PV>can stop a 165 tons plane at V1=155 Kts, you can stop the same plane
PV>at 125 tons and 145 Kts, even the computed V1 is 140Kts
I'm not sure I fully understand your point but will try to clarify.  The 
definition of V1 is a "Speed to which you can accelerate with both 
engines operating to critical engine failure speed and experience an 
engine failure and either continue the takeoff or stop in the remaining 
distance".  This speed varies with the weight of the aircraft and 
assuming that you have a balanced field length.  If I understand you 
correctly it sounds like you are refereeing to some degree of what we 
call "Refusal Speed"  That being the "Speed to which you can accelerate 
with all engines operating, experience an engine failure and stop in the 
remaining runway distance".
The main point I believe that you are making is that stopping distances 
vary.  Some factors are: 1.  Reaction time.  2.  Degree of Brake 
application.  3.  Condition of brakes (new or worn).  4.  Condition of 
tires (new or worn).  5.  Runway conditions (physical, winds or 
weather).
These speeds are flight checked during aircraft certification, 
transpolated into computers and certified as being the gospel and 
inserted into the Operating Manuals.
Good point you make however and glad to hear from you....Jim....
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 X CMPQwk 1.4 #1684 X Do you work? No I'm an Airline Pilot
--- Maximus/2 3.01
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