Just to come back to the Boeing way of doing things, these are for the 777, fixed weight, first 2 are balanced V-speeds with Full Thrust and 20% Derate, you can see that there is a slight differnce in V2.
#3 and #4 are OPTIMUM Vspeeds, with Full Thrust and 20% Derate, once again you can see a diffence in V2. So saying that V2 is constant regardless of the Thrust is incorrect.
Speeds are taken from a certified electronic flight manual.
Takeoff Speeds
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V1 = 147.8 KIAS
VR = 153.9 KIAS
V2 = 160.5 KIAS
Takeoff Speeds with 20% Derate
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V1 = 154.4 KIAS
VR = 156.6 KIAS
V2 = 159.4 KIAS
Critical Limit Weight Speeds
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Min V1 = 151.6 KIAS
Max V1 = 166.5 KIAS
Bal V1 = 160.2 KIAS
VR = 166.5 KIAS
V2 = 171.3 KIAS
Critical Limit Weight Speeds with 20% Derate
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Min V1 = 169.9 KIAS
Max V1 = 169.9 KIAS
Bal V1 = 169.9 KIAS
VR = 174.7 KIAS
V2 = 177.2 KIAS
Photon, once again i have to ask, what aircraft are you talking about? You have a pretty strange way of doing these calculations. Packs on/off to justify if you need to reconfigure at 1500 feet is pure and utter BS!
Mutt