When heavy and with more drag, you are likely to be performance-limited at 2nd segment. V2min is normally way below Vx, so increasing VR/V2 where runway length permits will improve 2nd segment performance.

With light aircraft, you are unlikely to be limited, so V2 will be V2min, which is obviously lower for a configuration with more lift at low speeds (CONF 3).

IIRC the calculation searches for results with the best gradient (the highest permissible tkof weight in disguise). So to overcome the drag penalty of F3, higher V2 is chosen - it suggests that it climbs better with higher speed.

Aero theory supports that. Max L/D for a given configuration is pretty constant but in order to achieve it higher speeds are needed for higher weights. Perhaps F2 does not drag that much and the markedly higher speeds are not needed. Yet second-guessing an iterative algorithm is rather pointless.

You guys rock! :cool:Thank you!