enemy. Stealth While the basic principles of shaping aircraft to avoid radar detection were known since the 1960s, the advent of radar-absorbent materials allowed aircraft of drastically reduced radar cross-section to become practicable. During the 1970s, early stealth technology led to the faceted airframe of the Lockheed F-117 Nighthawk ground-attack aircraft. The faceting reflected radar beams highly directionally, leading to brief "twinkles", which detector systems of the day typically registered as noise, but even with digital FBW stability and control enhancement, the aerodynamic performance penalties were severe and the F-117 found use principally in the night ground-attack role. Stealth technologies also seek to decrease the infrared signature, visual signature, and acoustic signature of the aircraft. 4.5 generation The term 4.5 generation is often used to refer to new or enhanced fighters, which appeared beginning in the 1990s, and incorporated some features regarded as fifth generation, but lacked others. The 4.5-generation fighters are therefore generally less expensive, less complex, and have a shorter development time than true fifth-generation aircraft, while maintaining capabilities significantly in advance of those of the original fourth generation. Such capabilities may include advanced sensor integration, AESA radar, supercruise capability, supermaneuverability, broad multi-role capability, and reduced radar cross-section. The 4.5-generation fighters have introduced integrated IRST systems, such as the Dassault Rafale featuring the optronique secteur frontal integrated IRST. The Eurofighter Typhoon introduced the PIRATE-IRST, which was also retrofitted to earlier production models. The Super Hornet was also fitted with IRST although not integrated but rather as a pod that needs to attached on one of the hardpoints. As advances in stealthy materials and design methods enabled smoother airframes, such technologies began to be retrospectively applied to existing fighter aircraft. Many 4.5 generation fighters incorporate some low-observable features. Low-observable radar technology emerged as an important development. The Pakistani/Chinese JF-17 (block-3 variant) and China's Chengdu J-10B/C use a diverterless supersonic inlet, while India's HAL Tejas uses carbon-fiber composite in manufacturing. The IAI Lavi used an S-duct air intake to prevent radar waves from reflecting off the engine compressor blades, an important aspect of fifth-generation fighter aircraft to reduce frontal RCS. These are a few of the preferred methods employed in some fifth-generation fighters to reduce RCS. KAI KF-21 Boramae is a purpose-built joint South Korean/Indonesian 4.5-generation fighter program. See also Jet fighter generations List of fighter aircraft References Bibliography Aronstein, David C. and Albert C. Piccirillo. The Lightweight Fighter Program: