15. FSTD TRAINING TOPICS. As stated in § 61.156(b), the ATP CTP must include at least ten hours of training in an FSTD, qualified under 14 CFR part 60. Of the ten required hours, at least six hours of training must be completed in a full flight simulator (FFS), Level C or higher. Up to four hours of training may be accomplished in a Level 4 or higher FTD
http://www.nata.aero/data/files/gia/.../ac_61-138.pdf