I suggest that it is very necessary to keep in mind that V1, like a great many other things in this game of aviation, is a certification animal. The strict definition, while of obvious interest to the line pilot, is perhaps not so important as the methodology of the parameter's use as prescribed in the manufacturer's flight and operations manuals and other training material for the specific aircraft.
Airline performance engineering and flight standards management people, on the other hand, must have a good handle on what goes into the certification recipe for a given aircraft so that a company's prescribed procedures do not unconservatively conflict with the flight manual.
As a certification thing, V1 has specific meanings and requirements within the flight test, aerodynamics, and, ultimately, certification disciplines. Certification matters and definitions can, and do, change .. it is then very important that the 'correct' definition be sourced... far too often, training pilots look up the current rules and then endeavour to apply the current rules to an earlier certification philosophy... which may, or may not, be a sensible thing to do. By following the manufacturer's recommended practices (given that the wider Industry never knows more than a fraction of what went on with any given certification) we can have a reasonable confidence that line practice is consistent with the certification.
The question of reducing V1 needs to be looked at in some detail especially in the case of low weight takeoffs where the value may get tangled up with Vmcg considerations. Again, the manufacturer has all the certification detail... any given operator seeing a need to vary the manufacturer's recommendations would need to enter into discussion with the manufacturer to confirm that hidden hazards were not going to be exposed ....
Last edited by john_tullamarine; 1st September 2002 at 22:19.