The TH-13S was used as an instrument trainer by the U.S. Army.  The Army accepted the first of an eventual 265 examples in 1963.  This variant is 16 inches longer than the standard H-13 model and is powered by a turbocharged 260 HP TVO-435-25 piston engine.  The TH-13S can accommodate two passengers in addition to the pilot, and has a gross weight of 2,855 pounds.

SOURCE: Frontiers of Flight Museum