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Type 722-II Dagu class Landing Craft Air Cushioned

The Type 722-II (NATO code: "Dagu" = Sands II, also known as "Whale Sand" II) landing craft was seen by the West as a highly capable vessel on par with many Western designs, but external appearances were deceiving. Superficially similar in layout to the American LCAC, it was slightly smaller in dimensions and had to maximum weight about half that of the LCAC. But an "LCAC with Chinese characteristics" would have Chinese characteristics, which ultimately boils down to inadequate propulsion - a pervasive problem known locally as "heart disease". China has lagged Western engines by decades, and by 2020 had yet to close the gap.

In 1975, the Navy commissioned the 708 Insttute to develop models of medium-sized full-lift air cushion landing test boats. With the assistance of the industrial departments of machinery, aviation and other related industries in Tianjin, the boat was built and commissioned in 1979. In 1979, the Chinese Type 722 test hovercraft was successfully built, and the flexible apron bottom of the boat was installed around it. The total weight of the boat is 68 tons, the load capacity is 15 tons, the maximum speed is 50 knots, and the endurance is 165 nautical miles. The boat is equipped with a pad lifting fan, a watertight pontoon, a landing pad, a gas turbine, and propeller propulsion. It can be loaded with a heavy-duty truck or an infantry to strengthen the landing, reinforced with a load capacity of 15 tons. The hull is made of aluminum and equipped with 4 decommissioned aviation piston engines. The total power is 4 1100 kW, speed 89.8 km / h.

In 1980, the boat organized two long-range voyage tests: the first round trip between Tanggu and Qinhuangdao, the second time across the Bohai Bay, and the winding into the hill to Qingdao, with a total of about 800 nautical miles. The test results show that the stability, cushioning, maneuverability and rapidity of the boat are good. The mechanical parts, shafting and aprons can operate normally under careful maintenance, but the main engine had a high failure rate, high noise and poor corrosion resistance in the marine environment. Poor performance, especially with high volatility gasoline as fuel, did not meet actual combat requirements and can only be used as an intermediate test. From 1981 to 1982, the 708 Institute was the main one, along with the Navy and the 702 Institute, worked closely together to organize two wave-resistance and rapidity tests of the hull in the sea area of Qingdao and the East China Sea. Structural vibration, apron stress, strain and cabin noise testing provide first-hand marine experimental data for the development of practical models.

According to reports, the 722 test boat platform debugging required more ballast iron at the time, the shipyard only 5 tons of ballast iron was not enough for the corresponding weight of 10-20 tons. At that time, the funds were not plentiful. The shipyard did not purchase ballast iron. The earthwork was replaced by manual labor. The hundreds of people first weighed the weight, compiled the group by weight, and stood in the designated area according to the password. This method is actually better than ballast iron. The mobile ballast iron is also manually transported, and the manual ballast movement position is very convenient. The task is quickly completed with the test. At that time, it was dubbed "artificial ballast iron" by the workers' masters.

In 1983, the 409 gas turbine was successfully developed, each with a power of 2,205 kW, burning light diesel oil, meeting the practical requirements. Based on the 722 prototype boat, the 708 Institute used the Model 409 as the power source to design the 722-2 model of the coastal medium-sized full-lift type air cushion entry boat. In order to improve the life of the apron and improve the wave resistance, the boat changed to a low-resistance reverberation apron; in order to improve the seawater corrosion resistance of the hull structure, a newly developed magnesium-aluminum alloy was adopted. The boat is equipped with two 409-type gas turbines, coaxial branch-driven fans and ducted air propellers. The gas turbine power unit is used for hovercraft, and it is necessary to overcome the technical key such as machine, propeller joint control, air intake filtration, exhaust injection and low working condition navigation. To this end, after the successful delivery of the empty test of the test bench of the manufacturer, the single-machine joint control experiment of the specific conditions of the hovercraft was carried out, and the performance measurement of the variable working condition and the combined control of the machine and the propeller was carried out. In 1986, the simulations of the power plant on the land were successful.

After the improvement of the power system, the 722-II air cushion landing craft was developed. The performance of this type of boat has been greatly improved. The boat-mounted military equipment is equipped with two double-mounted 14.5 mm high-level machine guns, one on each side. In 1983, the 409 gas turbine was successfully developed, each with a power of 2,205 kW, using light diesel oil to meet practical requirements. Based on the 722 prototype boat, the coastal medium-sized air-cushion landing craft 722II was designed. The boat was featured a new low-resistance apron, which was made of magnesium-aluminum alloy to improve the corrosion resistance of the hull. It was equipped with two 409-type gas turbines, coaxial branch-driven fans and ducted air propellers to overcome the combined control of the propeller and the air intake and exhaust. Technical key to ejector and low-traffic navigation.

In 1986, various experiments on land were successful. Shipment was carried out in 1987. In 1988, the Dagu shipyard built the air-cushioned landing ship and began trials. In 1989, the sea and landing tests were successful and delivered. This is an important symbol of the Chinese hovercraft technology entering the practical stage.

Although the power of the 490 gas turbine was relatively suitable, the weight and volume were too large, which directly led to the low payload. Only 15-20 tons can only be loaded with an infantry fighting vehicle or an armored transport vehicle [compared to the 75 ton overload capacity of the American LCAC]. Therefore, the 722II air cushion landing craft was not built in batches. However, the boat fully possessed the basic characteristics of modern air-cushion landing craft, and the Navy used it for extensive testing, making a significant contribution to the improvement of the new landing method and the development of a new generation of air-cushion landing craft.

The biggest shortcoming of the 722II air cushion landing craft is that it was limited by the domestic technology level at that time and lacks the actual design experience of large air cushion landing craft. Due to the problem of small payload (only equivalent to the weight of two 5-ton heavy "liberation" trucks), the 722-II air-cushion landing craft was not mass-produced, but the boat was used in a large number of tests. The Chinese Navy has provided valuable experience in developing a new generation of landing craft. Due to technical obstacles however only one was built in 1989 and finally removed from service in 2001.

Each of the 722 and 722II models is retired. Model 722 Type 452 is in Haibo, Qingdao.




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Page last modified: 14-10-2019 19:10:35 ZULU