Angle Of Vanishing Stability (AVS)

The heel angle at which a vessel’s righting lever reduces to zero after its initial range of positive stability.

Before the AVS, the intact vessel normally has positive righting ability and tends to return towards upright when the heeling force is removed. Beyond it, the righting lever becomes negative and the vessel tends to continue towards inversion rather than recover unaided.

AVS is read from a stability curve and is only one measure of stability. Loading, free-surface effects, downflooding, movable weights, hull form and damage can materially change practical capsize behaviour.

Alternative Meanings:

Angle of Vanishing Stability (AVS)

The heel angle at which a vessel's righting lever becomes zero after remaining positive at smaller angles.

Beyond the AVS, the vessel's intact hydrostatic stability tends to continue the capsize until another stable attitude is reached, often inverted, rather than return it upright. The value is read from the righting-arm or GZ curve for a stated loading and watertight condition.

AVS is not a safe maximum operating heel angle and does not by itself predict capsize resistance or recovery in waves. Downflooding, free surface, shifting loads, dynamic energy, hull damage and deck openings can reduce effective survivability well before the theoretical angle.