Xian H-6
The Xian H-6 () is a licence-built version of the Soviet Tupolev Tu-16 twin-engine jet bomber, built for China's People's Liberation Army Air Force (PLAAF). Delivery of the Tu-16 to China began in 1958, and a licence production agreement with the Soviets was signed in the late 1950s. Xi'an Aircraft Industrial Corporation (XAC) manufactured aircraft at Xi'an as the "H-6"; the first flew in 1959. By November 2020, the PLAAF had as many as 231. The latest variant of the H-6 is the H-6N, a heavily redesigned version capable of aerial refueling and carrying air -launched cruise missiles. According to the United States Department of Defense, this will give the PLAAF a long-range standoff offensive air capability with precision-guided munitions. Design and development. The first domestically produced H-6 was completed in 1968 and evidence of bombing training was recorded by U.S. spy satellites on August 13, 1971. By March of the following year, the CIA estimated that the PRC had 32 aircraft operational with an additional 19 awaiting completion. The H-6 was used to drop nine nuclear devices at the Lop Nur test site. However, with the increased development in ballistic missile technology , the nuclear delivery capabilities that the H-6 offered diminished in importance. The CIA estimated in 1976 that the H-6 had moved over to a dual nuclear/conventional bombing role. Developed versions. Early variants of the original H-6 – a conventional, free-fall bomber – later built included the H-6A nuclear bomber and H-6B reconnaissance variant. Two subsequent variants had improved countermeasures: the H-6C (conventional bomber) and H-6E (nuclear bomber). The H-6D was an anti-ship missile (ASM) carrier and the HY-6 series were mid-air refueling tankers. The H-6D was introduced in the early 1980s, to carry the C-601 antishipping missile (NATO  codename "Silkworm"), an air-launched derivative of the Soviet P-15 Termit ("Styx"); two C-601s were carried, one under each wing. The H-6D featured various modernized systems and sports an enlarged radome with a Type 245 "Kobalt" I-band surveillance radar under the nose. The Type 245 radar was based on the Soviet PSBN-M-8 NATO codename "Mushroom" radar used on the Tupolev Tu-16. Earlier versions (Type 241, 242 and 244) were installed on the early models of the H-6. The H-6 has also been used as a tanker and drone launcher. Later H-6 production featured extended curved wingtips. Many H-6A  and H-6C aircraft were updated in the 1990s and merged into to the H-6F designation. The main improvement was a modern navigation system, with a GPS satellite constellation receiver, Doppler navigation radar, and inertial navigation system. New variants were produced in the 1990s: the H-6G was a control platform for ground-launched cruise missiles and the H-6H could carry two land-attack cruise missiles. In terms of the missiles carried, five immediate possibilities were considered by PLAAF: the indigenous HN-1, HN-2, HN-3, DH-10/CJ-10, and a variant of a Russian-designed cruise missile. The CJ-10 was apparently chosen as  the main missile carried by the H-6H. Subsequently, the H-6M cruise missile carrier was also introduced, with four pylons for improved cruise missiles and a terrain-following navigation system. Apparently these variants did not include internal weapons bays, and the designs also omitted most or all of the previous defensive gun turrets. H-6K. The H-6K, first flying on January 5, 2007, entered service in October 2009 during the celebrations of the 60th anniversary of the People's Republic of China, and is claimed to make China the third country with an active strategic bomber after US and Russia . With a reinforced structure making use of composite materials, enlarged engine inlets for Russian Soloviev D-30 turbofan engines giving a claimed combat radius of , a glass cockpit with large size LCD multi-function display, and a reworked nose section eliminating the glazed navigator's station in favour of a more powerful radar, the H-6K is a significantly more modern aircraft than earlier versions. Six underwing hardpoints for CJ-10A cruise missiles are added. The rear 23 mm guns and gunner position are replaced by electronic components. The H-6K is designed for long-range attacks and stand-off attacks. It  is capable of attacking US carrier battle groups and priority targets in Asia. This aircraft has nuclear strike capability. While previous models had limited missile capacity (the H-6G could only carry two YJ-12 anti-ship missiles and the H-6M two KD-20/CJ-10K/CJ-20 land attack cruise missiles), the H-6K can carry up to six YJ-12 and 6-7 ALCMs; a single regiment of 18 H-6Ks fully loaded out with YJ-12s can saturate enemy ships with over 100 supersonic missiles. Although the aircraft has a new nose radome housing a modern air-to-ground radar, it is not  clear if the bomber or other Chinese assets yet have the capability to collect accurate targeting information for successful strikes against point targets in areas beyond the first island chain. An electro-optical targeting system is fitted under the nose. The WS-18 (or WS-18A) engine may be intended to re-engine the H-6K. The WS-18 - a copy or derivative of the D-30 - began development in 2007 and flight testing in 2015. In 2015, about 15 H-6Ks were in service. A H-6K fitted with a refuelling probe may have first flown in December 2016. Besides extending range, a possible mission  for the variant may be to launch satellites or ballistic missiles. Defense Intelligence Agency chief Ashley confirmed that China is developing two new air-launched ballistic missiles, (CH-AS-X-13) one of which can carry a nuclear warhead. The H-6K would be suited to launch such missiles. In January 2019, Norinco announced it had tested an analog of the American "Mother of all Bombs." The weapon is carried by an H-6K and takes up the whole of the bomb bay, making it roughly long and weighing 10 tons. Chinese media claimed it could be used for wiping out  reinforced buildings and shelters as well as clearing obstacles to create an aircraft landing zone. Operational history. China has repeatedly used H-6 aircraft to perform long-range drills near Japan, prompting the Japanese Air Self-Defense Force to scramble fighters. December 2020 H-6, carried out joint patrols at an altitude of the Sea of Japan. In June 2021, a combat drill was conducted near Taiwan's air defense identification zone.