Class A aircraft use VSR, the stall reference speed,
rather than VS1 but it is substantially the same thing. The take-off safety
speed is the highest of:
1.13 VSR for two-engined and three-engined turboprop powered aeroplanes
and jet aircraft without provisions for obtaining a significant reduction in
the one-engine-inoperative power-on stall speed.
1.08 VSR for turboprop aeroplanes with more
than three engines and jet aircraft with provisions for obtaining a significant
reduction in the one-engine-inoperative power-on stall speed.
1.10VMC
VR plus the speed increment attained before reaching a height of 35 ft
above the take-off surface
A speed that provides adequate manoeuvring capability