Qustion:

When the FSM command is not used when calculating righting arms, the CG shift applies to the tanks and the righting arms are calculated using the fixed weight and center. In the situation where a tank is frozen, how does the software account for this weight when calculating righting arms? What effect does this have on righting arms and area? I note that it is not indicated in the fixed weight and center and the CG of the tank should not be able to shift.

Answer:

It is incorrect to think of the righting arms as being calculated using the "fixed weight and center". The fixed weight and CG are shown in the RA table header only to give some indication of the condition at hand (since the tank CGs are possibly shifting and maybe there's spilling, nothing else applies at all heel angles).

The righting arms are always calculated based on the total CG vs. the CB. Therefore it doesn't matter whether or not some tanks are frozen: they are always included in the total CG.

But you have a good point about the frozen tanks in that perhaps they should be included in the fixed weight and CG in the RA table header since as long as they are frozen they are certainly "fixed" as well. (Of course that wouldn't change any of the righting arms but it might be helpful to someone trying to understand how the frozen tanks are treated.)

Any time you have a question about how a righting arm is calculated, you can see the details by means of the STATUS report. For example, suppose that you wanted to know how the tanks are contributing to the righting arm at 45 degrees heel. You could do the following.

HEEL = 45
SOLVE TRIM
STATUS