So the changes were, but they were not outwardly visible.
This might help you:
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F-7 Skybolt / J-7 (Jian-7 Fighter aircraft 7)
F-7 MG is a single-seat, single engine light aircraft which was considered to be a well equipped modern fighter jet. Mainly used for bombing, F-7MGs has the capability to provide air-defence and ground support as well as capability to intercept. It has an operational range of 850 km. Inducted into the PAF in 1990, the F-7MP is the primary air defence fighter of the PAF.
Derived from the earlier MiG-21 model, the F-7MP embodies some 20 PAF specified changes including wiring for both PL-5, Sidewinder missiles, IFF equipment, Martin-Baker Ejection seats. PAF initially ordered 20 F-7Ps and later the upgraded 60 F-MPs, but taken delivery of another 80 aircraft. The initial F-7Ps have also been upgraded to the F-7MP standard. F-7MP equiped No. 2, No. 14, No. 15, No. 17, No. 18, No. 19 (OCU), and No. 20 and CCS Squadrons of the PAF.
The News reported that China dispatched five ships to Karachi in the span of about 10 days in December 2001 to step up the supply of new aircraft, spares and other defence equipment. The ships were loaded with cargo ranging from cartons of unassembled brand new combat aircraft and a variety of air force-related weapons and equipment. The brand new aircraft were believed to be F-7MG aircraft which Pakistan had ordered earlier. Pakistan ordered two squadrons, about 40-50 aircraft. The timely delivery of new planes from China enhanced the capability of Pakistan Air Force (PAF) by several squadrons of brand new F-7 fighter aircraft narrowing a 1:2 ratio of air force planes between India and Pakistan. India had about 800 out of which 715 are combat ready aircraft, Pakistan's had a strength of 400. The new deliveries increased PAF strength to 450.
The F-7MP is the second basic production version. All-weather interceptor with search-tracking radar in enlarged inlet cone. Increased inlet diameter and enlarged forward fuselage. More fuel in proportionally waisted mid-fuselage. Larger main landing gear with bulges below and above wing roots. Pilot boom moved above inlet. 'Fishbed-E' is a version with 2 GSh-23mm guns on fuselage pylon and redesigned brake parachute housing.
It was being fitted with the new Grifo airborne radar system called "Pulse Doppler Frequency Agility Radar" made in collaboration with Italy. The Grifo Radars, have the ability to track and scan, look up and down at the enemy aircraft. Offers to upgrade existing equipment are not just confined to the original manufactures. Israel, for example, has a MiG-21 upgrade package that competes with the Russian upgrade (such an upgrade was performed for Romania by Israel). Because the JF-17 was developed primarily for the PAF and export market, it provides a low-cost replacement for many developing countries that are currently operating the ageing MiG-21/F-7 Fishbed and Northrop F-5 series. The unit price is estimated to be US$15 million.
In March 2008 three female pilots of the Pakistan Air Force (PAF) graduated along with 20 male colleagues after completing their operational conversion course on F-7 fighter aircraft. "The PAF female pilots achieved yet another landmark. Through consistent hard work, dedication and exemplary spirit, they completed their operational conversion on F-7 fighter aircraft," a PAF press release said. It said the female pilots would now be deployed in different fighter squadrons of the PAF. Earlier, the graduation ceremony of 'Operational conversion course' was held at the PAF Base, Mianwali. Air Vice Marshal Faaiz Amir, Air Officer Commanding Northern Air Command, was the chief guest. Speaking on the occasion, Air Vice Marshal Faaiz Amir said, "As proud inheritors of glorious traditions, you'll not only be expected to live up to the finest examples of devotion, courage and professional excellence but also keep pace with the modern aviation trends to set new standards." He said, "The female members of the fighters' community, as pioneers, will not only be pace setters in professional standards, but in you lies the destiny of many aspiring young ladies who are keen to share your experiences and to decide about their future." Daily Times.
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http://www.globalsecurity.org/military/world/pakistan/j-7.htmhttp://www.globalsecurity.org/military/world/pakistan/j-7.htm