J-7 I and J-7 II
The Chengdu Aircraft Factory modified the J-7 from 1969 to 1975, in which it added a cannon, changed the inlet cone from a 3-stage adjustment process to a continuous adjustment, and modified the inlet lip. As a result, the J-7's short range firepower was improved, supersonic acceleration was increased, takeoff thrust was increased. Overall, the J-7's performance was vastly improved.
The Chengdu Aircraft Factory began to develop the J-711 based on the J-7 I in 1975 for further improvement in performance. Four additional important improvements over its predecessor were carried out after 1977:
- The canopy ejection was replaced by open rocket ejection and, therefore, the safe ejection was possible even at low altitude and low flying speed. The ejection escape system was used in an emergency to safely eject a pilot from the aircraft cockpit. On the basic J-7 aircraft the canopy was automatically engaged to the seat at the beginning of ejection and separated from the seat after ejection. It was prone to failure because of the complicated structure and release mechanism. Open ejection was used on the J-7II, by which the canopy would be jettisoned prior to the ejection of the seat. This open ejection escape system encompassed a new rocket ejection seat and new features in its maintenance, convenience, safety and reliability. An aft-hinged canopy was designed for this escape system and it suited the physical size of the Chinese pilots. A rocket pack was incorporated into the new Type II rocket eject seat to increase the ejection height and safe separation was ensured by the addition of a seat / pilot separation system. Over 300 ejection tests both on the ground and air demonstrated improved ejection capabilities at zero altitude and low-speed conditions. Safe escape at low altitude and at 250-850 km/h IAS could be performed. Design was certificated in 1979 and it first succeeded abroad in 1984. By the end of 1985 the Air Force used the ejection system 5 times and each time was successful [other accounts report that the new rocket ejection system worked successively in six real ejections from 1980 to 1985]. In 1985 Type II rocket ejection seat won a National Gold Medal of Quality.
- Relocation of the drag chute bay improved aircraft landing performance and shortened the landing run. A raised drag chute bay that deploy the drag chute at a higher landing speed for increased landing performance. With this improvement the aircraft could deploy its drag chute when the aircraft height above the ground was less than 1 meter and the landing run was reduced to less than 800 m.
- A 720 liters center line auxiliary fuel tank was carried instead of the previous 480 liter tank for increased fuel capacity and extended range.
- The engine was changed from the WP7 to the WP7B. The WP7B improved and the thrust-to-weight ratio of the aircraft and the aircraft's overall performance. The WP7B had 12.8% higher thrust and 70% more afterburner thrust.
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