During the mid-1980s, as Embraer was working on the Short Tucano, the company also developed a new version designated the EMB-312G1. Also using a Garrett engine, the EMB-312G1 prototype flew for the first time in July 1986. However, the Brazilian Air Force showed no interest, and the project was dropped. Nonetheless, the lessons from recent combat use of the aircraft in Peru and Venezuela led Embraer to continue the studies. It also researched a helicopter attack version designated as the "helicopter killer" or EMB-312H. The study was stimulated by the unsuccessful bid for the Joint Primary Aircraft Training System program, in which Embraer teamed with Northrop Grumman. In 1991, one existing demo EMB-312 aircraft was modified as proof-of-concept prototype. The aircraft featured a 1.37-m (4.49-ft) fuselage extension with the addition of sections fore and aft of the cockpit to restore its centre of gravity and stability, a strengthened airframe, cockpit pressurization, and stretched nose to house the more powerful PT6A-67R (1.424 Shp) engine. The PT-ZTW, s/n 161, flew in September 1991. Two new prototypes EMB-312H with the PT6A-68A (1.250 Shp) engine were built in 1993. The second prototype PT-ZTV, s/n 454 (later PP-ZTV) flew for the first time in May 1993. It featured a reinforced wing skin developed for the model F, an improved glass cockpit, full pressurization system, electrical swing back canopy opening and zero-zero ejections seats. The third prototype PT(PP)-ZTF, s/n 455, flew in October 1993, as a twin of the s/n 454. The EMB-312H's design later served as a starting point for the EMB-314 Super Tucano, dubbed the ALX, and adopted by the Brazilian Air Force as the A-29.