The Citation II (Model 550) was developed to provide the same docile low-speed handling and good short-field performance as the preceding Citation I while addressing a primary criticism of that aircraft — its relatively slow cruise speed of around 350 kn (650 km/h) at altitude.[2] The II stretches the Citation I fuselage by 1.14m (3 ft 9in), increasing seating capacity to ten (two pilots and eight passengers) and gross weight to 13,300 lb (6,000 kg).Wingspan was increased by 5.1 ft (1.6 m), fuel capacity was increased from 544 US gal (2,060 L) to 742 US gal (2,810 L), and more powerful, 2,500 lbf (11 kN) Pratt & Whitney Canada JT15D-4 engines were installed for a higher cruise speed of 385 kn (713 km/h) and a longer range of 1,159 nmi (2,146 km).[5] The stretched Citation was announced in September 1976, it first flew on January 31, 1977, and FAA certification was awarded in March 1978.The T-47A was a modified version of the Citation S/II (Model 552) for the U.S. Navy, featuring a 5 ft (1.5 m) wingspan reduction and hydraulically boosted ailerons for enhanced maneuverability, 2,900 lbf (13 kN) thrust JT15D-5 engines, a cockpit roof window for better pilot visibility during hard maneuvering, strengthened windshields for protection against bird strikes during high-speed low-altitude sorties, multiple radar consoles, and the AN/APQ-167 radar system.It features new P&WC PW530A turbofans, modern Honeywell Primus EFIS avionics, a revised Citation Ultra interior and a trailing link main undercarriage.[14] Clifford expected a STC within 12 months, 21% faster long-range cruise, 29% longer range, 34% better single-engine climb rate and 20% better fuel efficiency.[14] By May 2007, Sierra Industries in Texas was also developing a similar modification, as 900 Citations qualify for it, directly as a broker and MRO provider, while Clifford should license its STC.[19] Clifford and its partner Stevens Aviation could also update the flight deck with Collins ProLine 21 avionics and refurbish the cabin.
Citation II/SP (model 551) front view
Several U.S. Navy T-47A radar systems trainers seen in 1989