Question:

There are two wing tanks (P/S) that are connected by a pipe near the top of the tank to allow cross-flooding. In attempting to best simulate what might happen between the tanks I modeled each tank with half of the pipe, split at centerline so that I could load the tanks individually. In reality, they are connected via a pipe. What do you recommend with regard to calculating the FSM for a tank cross connected at the top?

Answer:

I think your cross-connected tanks can remain separate parts. In this case it is only when the loading is nearly full that you have any transfer from one side to the other. Even then, the connecting pipe is such that I think you would not have a completely free surface shared by the tanks. If you are using RA /FSM in your stability runs, you can do almost anything you like with the FSM method for those tanks. If you want the FSM for the P & S cross-connected tanks to reflect a common free surface, you can use the FSM FREE assignment. A less extreme setting would be to use true FSM below a certain load fraction, and a higher FSM value above that load. For example, FSM (BLST_#5P.P) = TRUE, FREE @ 0.9