01/31/2013. Remarks by Johan Visschedijk: "To accommodate the General Electric J79 engine and generally improve handling characteristics, the seventeen Model 183-93-02 YF-104A-LO service trials aircraft (s/n 55-2955 to 55-2971) had a 5 ft 6 in (1.67 m) longer fuselage. They incorporated the following other changes: forward-retracting nose wheel, two additional fuel cells in the fuselage, and modified intakes with half-cone center-bodies. Aircraft initially fitted with the General Electric
XJ79-GE-3 turbojet (with maximum thrust rating of 9,300 lb/4,218 kg dry and 14,800 lb/6,713 kg with afterburner); later the J79-GE-3A with improved afterburner was standardized.
The first YF-104A was flown on February 17, 1956, and reached Mach 2 on April 27. Together with the first 35 F-104A production models, the seventeen YF-104As were involved in a protracted flight trials program during which airframe strengthening and local redesign were progressively introduced, various forms of flap-blowing were tested and a ventral fin was added to improve directional stability at supersonic speed. Some were also used to test wing tip racks for either 170 gal (644 l) drop tanks or Sidewinder infra-red guided air-to-air missiles.
