Z-7 Heavy Helicopter Zhishengji-7
In the mid-1960s medium helicopters had been put into mass production and light helicopters were being developed in the Chinese helicopter field. But the heavy helicopters still did not exist. Based on the needs of war preparation and training, the military Services requested to develop a heavy helicopter which could carry a reinforced platoon of troops. In 1969 the CAE decided that the design task of the heavy helicopter designated as Z-7 would be undertaken by the newly founded Helicopter Design and Research Institute and CAE owned factories and institutes would perform the main development activities. The Helicopter Design and Research Institute was assigned the design effort on the Z-7 Heavy Helicopter (HH) shortly after it was established in 1969. By early 1970, Vice President Marshal Ye Jianying indicated that the target of the heavy helicopter development project in China was clear, requiring this helicopter to carry a platoon of soldiers. But at that time the Cultural Revolution was in full swing, and various conditions were poor.
The Z-7 design concept was to use two WZ5A turboshaft engines driving a six-blade rotor, and new designs of rotor hub and gear box. The WZ5 was developed from the WJ5 (i.e. modification of the mechanical transmission and free turbine governor) by the Zhuzhou Aero-Engine Research Institute and the Harbin Aero-Engine Factory, and was produced in Jiangsu Province since 1976 for the Z-6 helicopter. The remaining parts and components should be as common as possible with the ones in the Z-5 and Z-6. The design targets were as follows: maximum takeoff weight 14,400 kg, payload 3,500 kg, maximum speed 240 km / h, maximum range 350 km and service ceiling 6,000 m.
Whether a fixed-wing aircraft or a helicopter, the control torque required to control surfaces is large, and human effort alone is difficult to achieve this without using a booster. When guiding the helicopter, all levers and the rocker arm are moving in space. Of course, the regularity of movement, can be precisely calculated by computer, but the result is not intuitive, and it is difficult to conduct an overall coordination. A slight negligence will cause the trolley or rocker arm to come across other part. Thus, a leading technical problem in the design was is the accurate measurement of individual trajectory of the levers of the rocker arm. In this way, systems design engineer from the map at a glance to see whether the movement control system will affect the work of other systems.
In a helicopter there are many moving parts, such as engine, rotor, tail rotor, the automatic orientation, and so on. Helicopters have vibration problems, particularly in these parts. Therefore, every lever of the control system, with its natural vibration frequency, had to avoid integer times of the speed of the moving parts, so as to avoid resonance. Because resonance will directly affect the functions of control system and its operating efficiency. To this end, dozens of levers of control systems in the Z-7 were subjected to natural frequency calculations.
China was ready to develop intercontinental ballistic missile, which is a major policy decisions that concern national prestige, and military prowess. In the summer of 1971, the central issue of the "718 Project" was the development of three main models of ships: "Yuanwang Hao " (the main measurement ship used for tracking and comprehensive measurement), "Xiangyanghong No.10" (an ocean survey boat) and "J121 Hao" (an ocean salvage lifesaving boat). However, the escort and salvage ships needed helicopters. At that time the situation was that missile development progress was assured and the ships were no problem, just waiting for the helicopter.
By May 1975 the manufacturing of 97 per cent of Z-7 parts and sub-assemblies had been completed, two airframes assembled and 90 per cent of vendor-furnished-equipment and components supplied. The WZ5A began 50-hour bench tests in 1978 and showed good results, meeting the performance target. The full size static test was completed in 1979. But the Z-7 was in the right place at the wrong time. But the limited national resource could not support at one time both the Z-7 and Z-8, two heavy helicopter development programs and the Z-7 program thus was terminated in 1979. The Z-7 was dropped in favor of the Z-8, which was a copy of the French SA-321G Super Frelon.
- 1962 - Vice President Marshal Ye Jianying demanded a large helicopter
- Autum 1966 - the Aviation Institute assigned the large helicopter development task to Harbin Aircraft Factory
- May 1967 - Harbin Aircraft Factory formed a development group and issued technical target of 4500kg cargo, 600km range, hover at 3000m and 30 degrees celsius, and the task was transfered to the Helicopter Design Institute
- March 1969 - The Air Force required development of a large helicopter, and later in the year the Aviation Institute decided to found the Helicopter Institute, engaged in the large helicopter development task, project code Z-7
- September 1969 - Helicopter Institute (not formally established until December) issued a proposal with maximum takeoff weight 22,600kg, but due to the unavailability of a powerplant, this was changed to a interim proposal equiped with 2 Wozhou-5jia engines
- 20 March 1970 - proposal was approved and full-scall development was initiated, with design by the Helicopter Institute, engine / deduction / transmission by Zhuzhou Engine Institute, and manufacture / assembly / test by the Flight Test Institute.
- 28 June 1979 task terminated after two airframes had been built and full-scale static test completed
|length (including blades)||25.31m|
|width, fuselage||5.19m (including short wings)|
|cabin: max height||1.95m|
|cabin: max width||2.1m|
|0.8m x 1m emergency exit in floor,|
|3.2m x 1.9m rear open for ramp|
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