In 1980, the Royal Thai government, seeking to extend the life of their C-123 fleet, placed a contract with the Monarco Aircraft Company, supported by the USAF, to convert a single C-123B to turboprop powerplants. Allison T56-A-7 turboprops were used, but by the time the aircraft, dubbed C-123T, was complete it had new wet wings, an Auxiliery Power Unit (APU) to assist with power steering of the control surfaces, and heating system for the cargo compartments that also fed a new deicing system. Budgetary restrictions forced the Thai government to abandon the program in 1981, and with a lack of interested parties development of the C-123T stopped. However, it concluded the life of the C-123 by making it the only (at least this is claimed) aircraft to operate as a glider, jet, combustion, and turboprop during its history.
This is C-123T 56-4357.