Preflight simulation analysis of flight experiment and flight test results are described. The automatic landing flight experiment was conducted in Woomera, Australia, in 1996, to develop the automatic landing technology required for the future Japanese uncrewed spacecraft. To ensure successful landings, computer simulation played an important role in the preflight analysis. Monte Carlo simulation was applied for the analysis. The root sum square method, which is commonly used in Japanese launcher rocket development projects, was also applied. Monte Carlo results were compared with the rss results and the flight test results. All 13 flight tests were successfully completed. Longitudinal guidance in the flare phase was found to be sensitive to some modeling errors. The cause is discussed.