The air frame is of semi-monocoque structure constructed primarily of aluminum alloys. High strength steel and titanium alloys are partially adopted in some critical areas. The air frame is designed for a service life of 4,000 flight hours or 25 years, the first overhaul being due at 1,200 flight hours. Block 2 JF-17s incorporate greater use of composite materials in the air frame to reduce weight. The retractable undercarriage has a tricycle arrangement with a single steerable nose-wheel and two main undercarriages. The hydraulic brakes have an automatic anti-skid system. The position and shape of the inlets is designed to give the required airflow to the jet engine during maneuvers involving high angles of attack.