Type 726 Yuyi-class hovercraft - Design

The Type 726 hovercraft is equipped with two gas turbines that drive four lift fans and two air propellers. The 726 initially did not use domestic gas turbines, but the UGT-6000 gas turbine produced in Ukraine, and the domestic QC-70 gas turbine will be used later. The GGT-6000 gas turbine has a length of 4.6 meters, a width of 1.8 meters, a height of 1.7 meters, a weight of 4.5 tons, a maximum power of 6,700 kilowatts, and a maximum output of 13400 kilowatts for a two-axis output. The power-to-weight ratio is approximately 84 according to the full displacement of 160 tons. kW / ton (LCAC is about 83 kW / ton), the 726 is basically guaranteed to have a maximum speed of about 50 knots below the third-class sea conditions (wave height 0.5-1.25 m).

The output power of the QC70 gas turbine is about 7200 kW, the air efficiency is 31%, the weight is about 2.3 tons, and the compressor is a 9-stage axial flow type. It is not difficult to see that compared with the UGT6000, the QC70, with its advanced core machine and advanced design, is more compact and lighter in weight, and uses the FADEC system (full-right digital engine). Control system), so the overall performance is better than the UGT6000 gas turbine. After the QC70 is equipped, the performance of the 726 air cushion landing craft will also be improved and improved.

The QC70 gas turbine was developed in 2003, and the chief designer is Li Xiaotang, deputy director of the Shenyang Engine Design Institute. When the media reported on the advanced deeds of him and his team, similar content appeared: the development and loading application of a small-scale power marine gas turbine with complete independent intellectual property rights was completed, which filled the domestic gap and became the development history of China's marine gas turbines.

The successful development of QC70 is of great significance, but encountered many twists and turns in the development process. In the first half of 2007, QC70 completed the durability test of the whole machine. However, it is speculated that the 726 type air-cushion landing craft has not been mass-produced, and it is likely that the technical appraisal has not been completed for a long time. Since 2014, the advanced deeds of Li Xiaotang and his team have been continuously seen in the media, which indicated that QC70 should complete the technical appraisal around 2014.

According to the 726 model of the 96-type tank test, its load capacity must exceed 45 tons. Considering that it should consider loading a larger 99 tank and a certain number of landing personnel, it is generally believed that the maximum load of the 726 landing craft is closer to 60 tons, its load factor is about 38%, close to 41% of LCAC. The 726 landing craft can be equipped with most of the tanks and armored vehicles of the Marine Corps or Army amphibious combat forces, and can be flexibly matched according to the equipment carried.

The front and rear of the boat deck are provided with a door and a ramp ["springboard"] for the personnel and the vehicle. The bollard and the anti-collision pad are arranged on both sides of the bow of the boat. The cockpit is placed on the left side of the crotch according to international practice, and the left gas turbine cabin door is monitored for observation of the left machine. The cockpit uses square portholes and has a good line of sight.

There are two main and co-pilots. The main driver is the officer. It is responsible for the operation and the navigation command of the boat. The first officer is the sergeant. The smooth flow of contacts also assists the officers in their operations and daily administration. At the top of the cab, navigation radar antennas, maritime satellite antennas, navigation lights, emergency lights, searchlights, spherical cylindrical communication antennas and other related equipment are installed. An inflatable life raft is placed at the rear of the cab. On the right side of the boat is a working and living cabin on the boat, which can accommodate 5 to 6 crew members.

The main and secondary guns are equipped with a light and a retractable high-precision 12.7 mm machine gun. At the rear of the shooting area is a fixed tilting flagpole for use with the hanging flag and a work light for night navigation and lighting. The second deck of the working compartment is also provided with an inflatable life raft, the right outer side has a round porthole, and the right inner side is provided with a door that enters the right gas turbine engine room. There is a main cabin on each of the left and right sides of the hovercraft, which has a set of gas turbine and exhaust pipe and a device for heat dissipation. A centrifugal pad lift fan compartment is provided at the rear of the left and right sides, and there is a padded fan and a gearbox. The left and right tails of the boat are powered fan ducts and variable pitch propellers and propeller guards. There is a rudder at the rear of each power fan duct, and there are 4 rudders. In the middle of the boat is a deck deck and mooring area, below the deck in the fuel oil tank, there is a ballast fresh water tank in the middle of the deck for the machinery inside the boat and water for daily life.

The seawater entering the well dock of the Type 071 dock landing ship reaches a specified depth which facilitates the rapid entry and exit of the 726 air cushion landing craft. However, the skill level of the hovercraft control skills requires a lot of practice and experience accumulation, especially the safe driving of the hovercraft into the dock door and tailgate requires some professional skills. The cockpit of the Type 726 is located on the left side of the boat. When the hovercraft enters and exits the tailgate of the mothership, the driver must visually check the distance between the boat and the tailgate of the mothership. When the boat approaches the tailgate of the mothership, it is forbidden to use for safe driving. The power propeller fan, which relies on the hull in full-lift state, "step-by-step" into the best position of the mother ship's tailgate, slowly enters into the dock of the mothership, and then fully lifts the boat. The body is positionally adjusted in the docking bay. After determining the parking position, the docking tank begins to drain until it is completely drained. At this time, the hovercraft is upgraded from full cushion to semi-air cushion.

Then gradually turn off the engine and lower all the air cushions. The 726 type hovercraft docking compartment is more convenient. In the floating state of the docking bay, the fully-lifted 726-type boat is adjusted to the nearest position of the docking cabin tailgate. The fan blade is started in a safe environment, and the reversing vehicle slides out of the docking bay. The tailgate is about 20 meters away, and the hovercraft can then enter the full pad lift in a safe state.

The driving skills of the 726 and 724 are significantly different. The 726 is big and has a certain degree of difficulty in handling. The 726's cab is not in the middle like the 724, but on the left side of the boat. This is difficult to visually estimate the spacing. If you do not have the practical experience of repeated driving, and carefully understand the correct method, it is very difficult to complete the training of the 726 type boat into and out of the mothership.