Yu'an J.29

Development


The J.29 can trace its origins to the late Great Kesh War, when the Kodeshian Air Defence Force was in desperate need of future tactical aircraft. In the mid 1950s the Air Defence Force adopted a new low-cost tactical fighter design for short-range roles and close air support to replace several types fighters and various light bombers then in service. Several existing designs could fill this role; the design which would become known as the Yu'an J.21 which was a light fighter with a secondary attack capability. The next month, a report on light tactical aircraft suggested the Air Defence Force purchase the J.21, and consider a new higher-performance aircraft to ensure its air superiority. This point was reinforced after the loss of many of its existing Dongfang J.52 air superiority aircraft to enemy forces.

In 1957, research studies were begun on a next generation type air superiority fighter. These early studies envisioned a production run of 800 to 1,000 aircraft and stressed manoeuvrability over speed a departure from earlier jet designs which focused almost exclusively on high speed performance; it also stated that the aircraft would not be considered without some level of ground-attack capability. Later studies lowered the required performance from Mach 3.0 to 2.5 to lower costs and speed up production.

An official requirements document for an air superiority fighter was finalised in 1955, and sent out as a request for proposals to 6 companies that same year. Meanwhile, the Yu'an J.21, quickly became the mainstay of the Air Defence Force which limited some of the urgency of the new air superiority design as the J.21 offered a credible air-to-air capability.

Four companies responded with proposals. Following a downselect, three companies were asked to provide further developments. In total, they developed some 600 design concepts. Typical designs featured variable-sweep wings, weight over 60,000 pounds (27,000 kg), included a top speed of Mach 2.7 and a thrust-to-weight ratio of 0.75. When the proposals were studied in 1958, the aircraft were roughly the size and weight of existing strike bombers were designs that could not be considered an air-superiority fighter.

The end of the Great Kesh War, led to a sudden but marked drop in defence spending and the next generation air superiority fighter proposals stalled until with the spending shifting towards the interceptor/strike fighter focused swing wing design Yu'an J.25 program. While air superiority was largely focused on improvements and futher development to the J.21 type.

But during the mid-1960s, international developments such as the ZuB-12 Stervyatnik, which was designed as a high-speed, high-altitude interceptor aircraft, and made many performance tradeoffs to excel in this role. Among these was the requirement for very high speed, over Mach 2.8. However, to observers, it appeared outwardly similar to an aircraft with high speed and a large wing offering high maneuverability, leading to serious concerns throughout defence establishment that it was superior to existing J.21 and possibly exceeding development of the J.25 then under development. Responding to these recent developments the next generation air superiority fighter program was restarted. Building on the combat experience from the Great Kesh War which missiles proved to be much less reliable than predicted, especially at close range. Combat pilots stressed that extra power and maneuverability were key aspects of a successful fighter design and these were more important than outright speed. A 1969 study proposed that the ideal design had a thrust-to-weight ratio near 1:1, a maximum speed further reduced to Mach 2.3, a weight of 40,000 pounds (18,000 kg), and a wing loading of 80 lb/ft².

In 1970, a request for proposals was released to major aerospace companies. These requirements called for single-seat fighter having a maximum take-off weight of 40,000 pounds (18,000 kg) for the air-to-air role with a maximum speed of Mach 2.5 and a thrust-to-weight ratio of nearly 1:1 at mission weight. It also called for a twin-engined arrangement, as this was believed to respond to throttle changes more rapidly. However, details of the avionics were left largely undefined, as whether to build a larger aircraft with a powerful radar that could detect the enemy at longer ranges was not clear, or alternatively a smaller aircraft that would make detecting it more difficult for the enemy.

Three companies submitted proposals, with the Air Defence Force eliminating Dongfang Aerospace Industries and awarding contracts to Yu'an Aircraft Industrial Corporation, Zhongbin Aircraft Company, and Nanbin Aircraft Corporation for the definition phase in 1970. The companies submitted technical proposals by 1971. The Air Defence Force announced the selection of Yu'an Aircraft Industrial Corporation that same year.

Design
The J.29 is an all-metal, construction. The platform features mid-mounted swept wing blended into the fuselage at the leading edge extensions and is essentially a cross between a swept wing and a cropped delta. There are swept tailplanes and two vertical fins, mounted on booms outboard of the engines. Automatic slats are mounted on the leading edges of the wings; they are four-segment on early models and five-segment on some later variants. On the trailing edge, there are maneuvering flaps and wingtip ailerons.

The J.29 has hydraulic controls and a three-axis autopilot but, unlike the many of its later contemporaries, no fly-by-wire control system. Nonetheless, it is very agile, with excellent instantaneous and sustained turn performance, high-alpha capability, and a general resistance to spins. The airframe consists primarily of aluminum and other metals and is stressed for up to 9 g (88 m/s²) maneuvers. The controls have "soft" limiters to prevent the pilot from exceeding g and alpha limits, but the limiters can be disabled manually.

Avionics
According to Yu'an Aircraft Industrial Corporation officials the J.29 uses a multi-mode fire-control radar designed in Kodeshia. The KONSAI-29 radar fire control system which includes the look-down/shoot-down coherent pulse-Doppler radar has a mechanically scanned planar array antenna and is capable of tracking 10 targets. Of the 10 targets tracked, 2 can be engaged simultaneously with semi-active radar homing missiles or 4 can be engaged with active radar homing missiles. For J.29B, the nose cone is modified to accommodate an active phased array airborne radar (AESA) radar. The KONSAI-29 radar was not a new design, but rather a development of the architecture used on the J.25. During the initial design specification period in the mid-1970s, Kodesian National Space and Aircraft Industry was tasked with producing a modern radar for the J.29. To speed development, KONSAI based its new design on work undertaken on the experimental radar program. Accordingly, the KONSAI-29 was originally intended to have a flat planar array antenna and full digital signal processing, for a detection and tracking range of at least 100 km against a fighter-sized target. Prototype testing revealed this could not be attained in the required timeframe and still fit within the J.29's nose. Rather than design a new radar, KONSAI reverted to a version of the J.25's twisted-polarization cassegrain antenna and traditional analog signal processors, coupled with a new digital computer to save time and cost. This produced a working radar system, but inherited the weak points of the earlier design, plaguing the J.29's ability to detect and track airborne targets at ranges available with missiles.

Cannon
Armament for the J.29 includes a single Zhongbin Zb.30-1 30 mm cannon in the port wing root. This originally had a 150-round magazine, which was reduced to 100 rounds in later variants.

Powerplant
The J.29 has two widely spaced Zhongbin Zb.130 turbofan engines, each rated at X kN (X lbf) dry and X kN (X lbf) in afterburner. The space between the engines generates lift, thereby reducing effective wing loading, hence improving maneuverability. The engines are fed through intake ramps fitted under the leading-edge extensions, which have variable ramps to allow high-Mach speeds. As an adaptation to rough-field operations, the main air inlet can be closed completely with mesh screens design in the main intakes for takeoff, landing and low-altitude flying, preventing ingestion of ground debris. Thereby the engines receive air through the mesh screens design in the main intakes.

Kodeshia
(Currently unknown)

Lestykhol
After tensions between Lestykhol and Kodeshia faded in the wake of the Kesh War, a trade agreement was made that allowed the purchase of J.29E's.

Variants

 * J.29A - Single-seat all-weather air-superiority fighter version.
 * J.29B - Improved single-seat all-weather air-superiority fighter version.
 * J.29E - Export model of J.29A with slightly downgraded radar with multiple target tracking ability. The aircraft can be fitted with active ECM systems, weapons guidance aids, improved built-in check and training systems.
 * JL.29T - two-seat operational conversion trainer.
 * JH.29A - Two-seat all-weather multirole strike version, it features improved engines, new avionics, new radar and reduced radar cross-section.; still in production.
 * JH.29D - Two-seat all-weather multirole electronic warfare variant. Equipped with wingtip electronic warfare pods.

Current
 Kodeshia  Gardarike  Lestykhol
 * Kodeshian Air Defence Force - 574 J.29 aircraft, including 176 J.29As, 150 J.29Bs, 70 J.29Ts, 54 JH.29A, and 24 JH.29Ds
 * Realm Air Defence - 228 J.29 aircraft currently in service, including JL.29T, JH.29A and JH.29D. J.29As received beginning in 1983 but retired as of 2018.
 * Lestykhol National Air Force - Received a number of J.29E and JL.29T aircraft beginning in 1985.