Please consider the following information, from a relatively new user of the CS757-200 FMC/CDU, with some measure of caution.  My problems may have derived from faulty FMC software, my PC operating system, FSX configuration or other unknown situations.

In earlier posts on this thread I expressed my wanting to know more about changing flight plans after the FMC created one and also my displeasure with the FMC in general.

I have done some further testing and have discovered some interesting points which have furthered my understanding of the CS FMC and allowed the creation of more successful plans.

1) Before a flight set the altitude in the altitude window greater than the maximum altitude in the flight plan, else the VNAV part of the plan will cease to be controlled by the FMC resulting with the VNAV light going off and the SPD light coming on. If the window altitude is set lower than the cruise value, the flight altitude will be restricted to the window altitude. If the window altitude is the same as the cruise altitude the plan just ceases to follow the plan at some yet undertermined point in the plan. It happened to me near the T/D point.  Very strange.

2) A plan from KSDF to KIND was created for a cruise alt of 15,000 ft. The resulting CS FMC plan  resulted in every leg having a speed of 316 knots and 15,000 ft including the VECTORS leg at the end of the flight. I thought, perhaps incorrectly, that the plan would have been created automatically with a descent of lower speeds and altitudes for the ending legs.

3) I manually entered into the VECTORS leg a speed of 160 and altitude of 3000. The EXEC light came on indicating it needed to be pressed. After pressing the EXEC light the plan was recalculated showing descending altitudes and lower speeds in the later legs. The changed values appear BOLD. This resulted in what I considered a successful plan. :)

4) Changed values of altitude and speed in the CDU seems to disable automatic following of the plan at the leg the changes were made and requires manual flight control. I would certainly like to know how to re-enable the flight plan to automatic.

I would be interested in knowing if any of these conclusions are just unique to my situation or experienced by others.