During the 1990s China imported number of fighter jets from abroad to directly equip the air force.(SU-27 from Russia) The new chief engineer Zhang Enhuo suggest using the imported fighter jet as test platform for the Taihang engine to reduce development risk of the project. And he applied for one import fighter jet as test bed for Taihang engine in his 1993 report to China Aviation industry corporation.
In June-7-1995, when the deputy chief of staff of the Central Military Commission Cao Gangchuan convey important decisions that Taihang engine should be the next engine to be equiped with J-10 and SU-27. As China should not be subjugated by other countries on fighter jet engines. This means they need to not only solve the test platform problem, but also need to solve the problem on follow up SU-27(J-11) engines. One engine for two types of figther jets, the importance of Taihang engine was raised to a new height.
It's became an important issue whether Taihang engine can be installed on Su-27 or not.That is also one of the controversial topics we debated a lot in the past. Is Taihang and AL-31 engine interchangeable without modification to the plane body, or the rear fuselage. Althought there are large numbers of facts proving there is no need for modification, but there are still misunderstanding with a lot of people, therefore I will try to clarify the relevant facts here.
First, like we already mentioned in the begining that J-10 was first originally installed with WP-15 engine and changed to AL-31, rather than from Taihang to AL-31. Secondly, the size of WP-15 is smaller than AL-31, while Taihnag prototype size is larger than AL-31. In order to install an engine larger than AL-31 on SU-27, One approach is to midify the back of the SU-27 to accommodate the larger Taihang engine, Another approach is to modify the size of the Taihnag to accommodate the Su-27's engine compartment. Since back then China still does not have the ability to modify the Su-27, therefore Taihang engine was re-design in adaptation of the Su-27 engine compartment.The theory of planes installed with AL-31 can not be installed with Taihang is just a misunderstanding. In fact from the compatible point of view alone, they are entirely feasible.
In addition, the J-10 modified fueslage is not to change engine, it's because of changed engine. The reason being some technical specifications did not achieve the original design specification after changing the engine from WP-15 to AL-31. And Song wencong decided to slim down the J-10 to meet the original design specification. But that's later on after the first flight of technology demonstrator.
From 1997 on the development focus shifted to the engine performance and adaptations design with the modified engine matching SU-27.Since China can't modify or can only make simple modification on SU-27 at the time. The main technical issues to be developed on the engine side for 606 institute to resolve. Before the metal prtotype design, Shenyang and 606 institute did technical coordination from aerodynamic and structural designs to demonstrate concrete ways for installing the engine. After several design changes to address the afterburner cylinder turn 5 degrees, afterburner ignition overrun, after casing modification, rerouting external piping and fittings and other problems (by the change on the engine casing, turbine starter drive also on the lower shaft by the change), the overall design for installing the modified Taihang engine was finally completed.
Meanwhile, From 1997 on Taihang's engine testing time doubled the numbers of pervious year annually.The engine ground test bed design and adaptations advanced simultaneously. At the time level one broken fan blade failure was once a stumbling block for the development work, the design has to be modified to take various measures to strengthen the root of the fan blades, so that the breaking point stress level greatly reduced, to meet the reliability requirements of engine test. Taihang engine test also revealed problems in control, the control system used a new technology Full authority digital engine (FADEC), the stability, reliability and robustness needs certain period to be address and mature, but it will affect the Taihang engine's overall capacity of flight test schedule, Zhang Enhuo decided to use mechanical hydraulic scheme to speedy the project.
In March 1998, J-10 prototype first flew. And in May the General Armament Department approved "Taihang" engine from being first install on J-10 to Su-27 instead. And Taiheng would be adjusted and finalized the design on Su-27. In September the same year, Shenyang, Shen Fei in cooperation with LiMing completed the installion of the engine on the full-size metal prototype aircraft, it only took one hour and half to complete the installion, further evidence of the "Taihang" engine will match the aircraft. In December, mechanical hydraulic scheme Taihang engine was tested, after a rigorous assessment verification, to ensure reliable operation of the engine. Thus, the original FADEC scheme is adjusted to be second in line, to be mature and then replace the mechanical hydraulic control program.
October 2000, 624 insititue Jiangyou station finally have the ability for high-altitude test for high-thrust engine. Altitude simulation test is to verify the reliability of aircraft engines, the ability to work within the flight envelope of the important test. Taihang engine has carried out four tests on the engine features, performance, thrust transient, off afterburner, inlet distortion, high altitude, high temperature and other characteristics were examined.
By the end of 2000 and early 2001, the factory that manufacture engine components deliver was a full year later than planned, the last engine parts was finally deliver on November 20 to 606 insititue. After working overtime, the aircraft was finally equipped with a Taihang engine in accordance with agreement and on time delivered to SAC at end of the year.
On June 6, 2001, A Su-27 mounted with one Taihang engine on the right side of the engine compartment completed its first test flight on SAC runway. By mid-October, the Taihang engine through two phases which lasted more than four months of test flight, successfully finish engine flight test ahead of schedule.
Part 2 II
In 2002, after completion of flight tests prescribed for Taihang, A J-11 was equipped with two Taihang engines for research flight testing. Thus, the Taihang engine enter the phase of finalizing design. During the engine prototype development stage, new materials powder metallurgy was used on high pressure turbine disk. Since the domestic technology is not yet mature at the time. Zhang Enhuo shouldered immense pressure deciding to replace high
temperature turbine disk material from FGH95 powder alloy to high temperature alloy GH4169. In fact, the turbine blades were also replaced from DD3 single crystal blades to DZ125 directionally solidified alloy blades.
In the same year, due to the Taihang engine repeatedly delayed, China have to continue to buy Russian AL-31F / FN (AL-31FN 54 engines) for the J-10 and J-11 production, making the AL-31 from "transition" engine to be the official column installed engine. And for the first flight of J-11B which was planned to use the Taihang engine, it's prototype also have to use AL-31F engines for flight test.
And then an incident happen where mechanical failure caused the left side engine stalled during test flight in mid air. Although the plane was safetly landed with one engine as the heroic pilot kept his calm and accurate judgment of the situation with his swift actions, and 606 insitiute can have the opportunity to find the reasons for the engine failure. But it also mean finalizing test flight of the engine did not pass the test.
This serious incident attracted the head of the central military commission, the General Armaments Department, National defnese and Air Force superiors's attention. A leader from the general armaments department paid a special visit to AVIC 1, and had a short conversation with general manager Liu GaoZhuo. Although the tone of the discussion was very gentle, but the company leadership was in shock to learn that if they were unable to fix and troubleshoot the engine problems quickly, Taihang project would be cancel.
On March-6-2005 Shenyang Aeroengine Research Institute (606 Institute)mobilized a pledge rally for finalizing the design of Taihang engine.Every staff from the 606 institute sign on the pledge to complete the project.On Dec-28-2005,the Taihang engine pass the test in Shenyang Institute of Design smoothly through the finalizing design review, Taiheng finally got the permit to fly the blue sky.
March-2006, Taihang was officially finalized and the model was made public. And the development of Taihnag moved to the new stage of batch production. In the same year, a prototype of J-11B number 04 was installed with Taihang engines. Later that year promotional materials of Taihang engine was shown on the seven Zhuhai Air show for the first time.
The development process of Taihang gone through many hardships, but road of batch production was also full of thorns.
In 2007, The first J-11BS prototype equipped with Taihnag engines successfully complete it's first flight. This model of aircraft's first flight, test flight, finalizing design of the aircraft were all done with Taihang engines. J-11B design was finalized the same year, but prototype 004 which installed with Taihang had a serious accident during flight test. Therefore the original plan to use Taihang engines on J-11B was cancel and change back to use AL-31F instead. In that same year China imported 100 more AL-31FN engines for J-10A/S.
