Xi'an Y-20
The Xi'an Y-20 () is a large military transport aircraft. The project is being developed by Xi'an Aircraft Industrial Corporation and was officially launched in 2006. The official codename of the aircraft is Kunpeng (), after the mythical bird that can fly for thousands of miles described in the ancient Chinese Taoist classic "Zhuangzi". However, within the Chinese aviation industry itself, the aircraft is more commonly known by its nickname Chubby Girl (), because its fuselage is much wider compared to other aircraft previously developed in China. Development. The aircraft was primarily designed and developed in China under Xi'an Aircraft Industrial  Corporation. In late 2020, Y-20 starts to incorporate indigenous WS-20 engines. The base model of Y-20 was further developed into the Y-20U as aerial refueling tankers which was introduced in late 2021. Design. The Y-20 uses components made of composite materials. The composites are now produced in China, whereas in the past they had to be imported. The Y-20's cabin incorporates flame-retardant composites developed by the 703 Institute of the China Aerospace Science and Technology Corporation (CASC). The 703 Institute was created in March 2009 with development taking three years. The performance of the composites is reportedly comparable  to those that fulfill FAR Part 25.835. The 703 Institute achieved another milestone by establishing a comprehensive Chinese evaluation and certification system for aircraft composite materials based on international standards. The Y-20 is the first cargo aircraft to use 3D printing technology to speed up its development and to lower its manufacturing cost. Model-based definition (MBD) is also used, and it's the third aircraft to utilize MBD technology in the world, after Airbus A380 (2000) and Boeing 787 (2005). A project team to implement MBD for the Y-20 program was formally formed in October 2009, and after the  initial success in application on the main landing gear, MBD application was expanded to the entire aircraft and became mandatory for all contractors and sub contractors of the Y-20 program. The implementation of MBD was initially met with strong resistance, with only a third of suppliers agreeing to implement MBD. However, the general designer of Y-20 declared that those who refused to implement MBD will be banned from participating in the Y-20 program, thus forcing everyone to comply, resulting in increases in productivity. The implementation of MBD greatly shortened the time required, for example, without MBD, installation of wings takes  a month or two, but with MBD adopted, the time is drastically shortened to just a few hours, and in general, the design work reduced by 40%, preparation for production reduced by 75%, and manufacturing cycle reduced by 30%. In addition to 3D printing, the Y-20 is also the first aircraft in China adopting associative design technology (ADT) in its development. Headed by the deputy general designer of structural design, Mr. Feng Jun (冯军), the initial attempt to implement ADT actually failed after two months spent on application on the nose section. It was only after the second attempt that  took another three months on the application on wings did ADT became successful. The adaptation of ADT greatly shortened the development time by at least eight months, and modification of wing design that previously took a week is shortened to half a day. Cargo is loaded through a large aft ramp that accommodates rolling stock. The Y-20 incorporates a shoulder wing, T-tail, rear cargo-loading assembly and heavy-duty retractable landing gear, consists of three rows, with a pair of wheels for each row, totaling six wheels for each side. The structural test was completed in 194 days as  opposed to the 300 days originally planned, thanks to the successful development and application of an automated structural strength analysis system. In comparison, similar work for the Xian JH-7 took a year. According to the deputy general designer, the shortest take-off distance of the Y-20 is 600 to 700 meters. Y-20 incorporates a total of four LCD EFIS, and the development of EFIS for Y-20 utilizes virtual reality via helmet mounted display. Eight types of different relays used on Y-20 are developed by Guilin Aerospace Co., Ltd. a wholly own subsidiary of China Tri-River Aerospace Group Co., Ltd.(中国三江航天集团 ), which is also known as the 9th Academy of the China Aerospace Science and Industry Corporation (CASIC). It was reported that the Y-20 started ground testing in December 2012, including runway taxi tests. The aircraft made its maiden flight lasting one hour on January 26, 2013. During landing in first flight, it was reported that the Y-20 prototype bounced once before finally settling on runway due to high landing speed. In December 2013, a new Y-20 prototype took to the sky. On 6 February 2016 pictures of the fifth prototype (serial number 788) in flight appeared on Chinese military webpages . Other known prototypes carry identification numbers 781, 783 and 785. On 27 January 2016, former Chinese test pilot, Xu Yongling, had reported in a Xinhua article that Chinese aviation industry officials had stated that the Y-20 "had completed development" at the end of 2015. In June 2016, the first two Xian Y-20 aircraft were delivered to the People's Liberation Army Air Force (PLAAF). Propulsion. The Y-20 is currently powered by four 12-ton thrust Soloviev D-30KP-2 engines, and all early production units are fitted with the same engine. The Chinese intend to replace the D-30 with the 14-ton  thrust Shenyang WS-20, which is required for the Y-20 to achieve its maximum cargo capacity of 66 tons. The WS-20 is derived from the core of the Shenyang WS-10A, an indigenous Chinese turbofan engine for fighter aircraft. Single-engine testing with the WS-20 may have occurred by February 2019. Four-engine testing may have occurred by November 2020. In 2013, the Shenyang Engine Design and Research Institute was reportedly developing the SF-A, a 28700-pound thrust engine, for the Y-20 and the Comac C919. The SF-A is derived from the core of the WS-15. Compared to the WS-20 , the SF-A is a conservative design that does not seek to match the technology of more modern engines. Testing with the WS-18 may have occurred by late 2017. Compared to the D-30, the WS-18 is 300 kg lighter, weighing in at 2000 kg; with thrust increased from 12.5 per ton of the D-30 to 13.2 per ton; and fuel consumption of the WS-18 is also reduced in comparison to the D-30, and the mean time between overhaul of the WS-18 is 3000 hours. However, because the increase in thrust is not significant in comparison to the D-30, the WS-18  is likely to be a stopgap measure before the WS-20 is ready. Cargo capacity. The Y-20's four-meter tall hold can lift up to 66 tons, and transport up to 2 Type 15 tanks or 1 Type 99A tank over a distance of 7800 km. Operational history. In 2014 the PLA National Defence University's Center for Economic Research recommended the purchase of up to 400 Y-20s, comparing the PLAAF's needs with the existing airlifter fleets of the United States and Russia. In June 2016 "Jane's" reported that up to 1,000 Y-20s are being requested by the  Chinese military. On 6 July 2016 the first serial Y-20 (serial number 11051) was handed over to the PLAAF in a ceremony. The second aircraft numbered 11052 followed soon after - it was assigned to the 12th Regiment of the 4th Transport Division at Qionglai, Chengdu. On 8 May 2018, it was announced by PLAAF's spokesperson Shen Jinke that Y-20 had "recently conducted its first joint airdrop training with the country's airborne troops". Starting November 2018 there were rumors about an aerial refueling variant of the Y-20. It is very appreciated for PLAAF because the largest domestically made aerial  refueling aircraft is HY(Hong You, meaning "Bomber/Fuel Tanker")-6, whose capacity is limited. On 13 February 2020, the Y-20 was part of a fleet used to deliver supplies and personnel to Wuhan. The operation was part of an effort to mitigate what became the COVID-19 pandemic. A fleet of 11 aircraft was used to deliver 2,600 military medical staff to Wuhan. The PLAAF fleet of 11 aircraft consists of 6 Y-20s, 3 Il-76s and 2 Y-9s transport aircraft. On 27 January 2022, two Y-20 aircraft arrived in Tonga after travelling over 10,000 kilometers from Guangzhou Baiyun, delivering 33 tons of  supplies including food, fresh water, water purifiers and tents due to the 2022 Hunga Tonga–Hunga Ha'apai eruption and tsunami. On 9 April 2022, six Y-20 aircraft landed at Belgrade Nikola Tesla Airport in Serbia, reportedly delivering a shipment of FK-3 surface-to-air missile systems. Controversy. On July 13, 2016, Chinese national Su Bin pleaded guilty, and admitted to charges that he conspired with others to hack into U.S. defense contractor Boeing and steal documents related to the development of the C-17, F-22, and F-35 aircraft. Once the information was stolen, he admitted to analyzing and translating documents from  English to Chinese, which he then emailed to the Second Department of the People's Liberation Army General Staff Department. Su Bin admitted he did so for financial gain, and sought to profit from the data that was stolen. In addition to financial gain, court documents revealed, in emails to the Second Department of the PLA, Su Bin noted the information, "...has extremely vital significance in our country's speeding up the development," of Project A, revealed to be China's program to develop the Xi'an Y-20.