The Chinese J-7B fighter was developed from the J-7A,it took the first flight on December 30th,1978.The biggest improvements are the application of the new WP-7B engine and the new generation escape system.The WP-7B engine have the greater thrust than the former engine and the service intervals of the engine is 200 hours which means the engine is much more reliable than before.The new ejection seat were applied in 1984,and soon made 5 times of successful eject in the following year. Besides, the other improvements includes the repositioning of the parachute compartment,the newly designed canopy and windshield and an extra fuel tank were added .