To get the FMC to calculate a T/D you have to play around a bit with the last waypoints before the runway. Delete the waypoints, get rid of the discos, execute, and add the deleted waypoints back into the the flightplan, get rid of the discos, and execute and maybe you will have a T/D. I say maybe because you might have to do it all again using a different combination of waypoints. But you have ample time because all this can only be done once you are airborne. A gem of an FMC

Michael Cubine