46 CFR §154.407

1. (a)For the calculation required under § 154.406(a)(1) and (b), the internal pressure head (heq), must be determined from the following formula:
2. (b)The (hgd) max is determined for the β direction, on the ellipse in Figure 1, which gives the maximum value for hgd.
3. (c)When the longitudinal acceleration is considered in addition to the vertical transverse acceleration, an ellipsoid must be used in the calculations instead of the ellipse contained in Figure 1.