of Mines & Technology, funded by the National Science Foundation, and operated in this capacity from 1969 to 2005. SDSM&T was planning to replace it with another modified, but more modern, former military aircraft, specifically a Fairchild Republic A-10 Thunderbolt II. This plan was found to carry too many risks associated with the costly modifications required and the program was cancelled in 2018. Aerobatics and warbird display Many retired T-28s were subsequently sold to private civil operators, and due to their reasonable operating costs are often found flying or displayed as warbirds today. Variants XT-28 Prototype; two built. T-28A U.S. Air Force version with an Wright R-1300-1 radial engine driving a two-bladed propeller; 1,194 built. T-28B U.S. Navy land-based trainer version with Wright R-1820-86 radial engine driving a three-bladed propeller and fitted with a belly-mounted speed brake; 489 built from new and 17 converted from T-28. T-28C U.S. Navy version, a T-28B with shortened propeller blades and tailhook for carrier-landing training; 299 built. T-28D Nomad T-28Bs converted for the USAF in 1962 for the counter-insurgency, reconnaissance, search and rescue, and forward air controller roles in Vietnam. Fitted with two underwing hardpoints. The later T-28D-5 had ammo pans inside the wings that could be hooked up to hardpoint-mounted gun pods for a better center of gravity and aerodynamics; 321 converted by Pacific Airmotive (Pac-Aero). T-28 Nomad Mark I - Wright R-1820-56S engine (1,300 hp). T-28 Nomad Mark II - Wright R-1820-76A (1,425 hp) T-28 Nomad Mark III - Wright R-1820-80 (1,535 hp) Fairchild AT-28D Attack model of the T-28D used for Close Air Support (CAS) missions by the USAF and allied Air Forces in Southeast Asia, which were nicknamed "Tangos" by their pilots. It was fitted with six underwing hardpoints and the rocket-powered Stanley Yankee ejection seat; 72 converted by Fairchild Hiller. YAT-28E Experimental development of the counter-insurgency T-28D. It was powered by a 2,445 hp (1,823 kW) Lycoming YT-55L-9 turboprop, and armed with two .50 in machine guns and up to 6,000 lb (2,730 kg) of weapons on 12 underwing hardpoints. Three prototypes were converted from T-28As by North American, with the first model flying on 15 February 1963. The project was canceled in 1965. T-28S Fennec Ex-USAF T-28As converted in 1959 for use by the French Armée de l'Air, replacing the Morane-Saulnier MS.733A. It was flown by their Escadrilles d'Aviation Légère d'Appui (EALA; "Light Aviation Support Squadrons") in the