The two-seat Shenyang development of the MiG-19SF, the FT-6, is not widely known, despite service with Egypt as well as Pakistan.
Although the Soviet Union built a small number of MiG-19UTI two-seat trainers, the V-VS concluded that a two-seat MiG-19 conversion trainer was unnecessary for transitioning and production was terminated, and the Shenyang-built FT-6 appears to owe little or nothing to its Soviet predecessor.
Whereas the Russian tandem two-seat modification was accommodated within the existing fuselage, the forward section of the FT-6 was lengthened by some 33 in (84 cm) over the original 41 ft 4 in (12,6 m), (without the long nose pitot) by the Shenyang design team to allow room for the second occupant.
This necessitated the addition of two more ventral strakes beneath the rear fuselage as compensatory side area to prevent snaking, giving the FT-6 a total of three strakes in all.
Other differences from the standard F-6 are few, although, in view of the already very limited endurance, to make up for the loss of fuel capacity resulting from the second cockpit, extra tankage had to be provided. A prototype two-seater appeared with small tip-tanks to rectify this deficiency, but these apparently proved unacceptable on a 58-deg (leading edge) swept-wing. The solution adopted on production FT-6s was to remove the two 30-mm NR-30 wing-root cannon and insert extra fuel tanks in their bays, leaving only the single similar weapon under the nose for armament training. This leaves the FT-6 with only 150 or so litres (33 Imp gal) less fuel than the single-seat version and allows a safe average training sortie time of about 45 minutes.
With the same twin Tumansky RD-911-811 (WP-6) axial-flow turbojets as the single-seat F-6, with a military rating of 5,732 lb (2600 kg) each, or 7,165 lb (3 250 kg) with reheat, the FT-6 offers virtually identical performance and handling to the F-6, with a maximum limit speed of around Mach 1.25-1.4, and a nominal low-level supersonic capability in the clean configuration of some 723 knots (1340 km/h). At a gross weight of around 19,274 lb (8 742,5 kg), with two 167 Imp gal (760 lt) drop tanks, the F-6 has a thrust/weight ratio of 0.86:1. The F-6's low-speed stability and handling are somewhat critical, particularly for inexperienced pilots, and the requirement for a two-seat version for conversion training is therefore logical.
Pakistan received its first FT-6s in September 1980. Transitioning pilots complete 20 dual landings in the FT-6 before going solo, plus about 66 sorties in the F-6 to complete the OCU course.
In the opinion of the PAF, the F-6 is probably the cheapest combat aircraft to operate of any in its class, and costs about one-sixth as much as the Mirage III or 5 per flying hour. Both types have about the same manpower requirements, at around 50-60 maintenance man-hours per flying hour, but spares for the F-6 from China are very considerably cheaper. The F-6 has suffered from the limitations of very short component lives - engine TBO, for example, is only 100 flying hours, and 600 hours for the airframe.