According to foreign media reports on September 21, the Philippine air force has received four a-29 “super Toucan” propeller type light attack aircraft. Just before that, Afghanistan also received four a-29s, and the delivery ceremony was held at the Kabul International Airport on September 17. The delivery brings the number of a-29 owned by the Afghan air force to 23. According to science and technology daily, a-29 has been participating in operations in Afghanistan since the beginning of 2016 and is the only fixed wing fighter of the Afghan air force. At present, the aircraft made in Brazil has been sold to many countries. Nigeria is also one of the new users of the aircraft. Not long ago, the first a-29 ordered by Nigeria completed its first flight in the United States. The popularity of the a-29 makes the propeller aircraft come into people’s eyes again. In this regard, military expert Wen Chang said, “from the picture, the a-29 is quite like a” master machine “during World War II. However, this aircraft has attracted the attention of the US military for many times in the past ten years, and equipped with air forces of many countries. In fact, the main reason why the a-29 can adapt to the anti-terrorism war and has been selected by the United States as the “designated” aircraft of the Afghan air force is that it is cheap, easy to use, and substantial. < p > < p > according to public data, the a-29 was jointly developed by Embraer and Sierra Nevada in the 1990s. It is one of the most popular basic trainer and light attack aircraft in the world. It is equipped with a turboprop engine with a flat lower single wing configuration. Its maximum take-off weight is 3.6 tons, and the bomb load is 1.5 tons. For a light aircraft, such a load is not small. < / P > < p > as a propeller aircraft, the stall speed of a-29 is only 148 km / h, and a car can catch up with it, so that the pilot can easily search and identify the target. It has a range of 2855 km and a endurance of 8 hours, which means it can hover over the battlefield for a long time. Wenchang pointed out that the war in Afghanistan has entered the stage of protracted war for nearly 20 years. Using expensive aircraft, such as B-1B and B-52 bombers and A-10 attack aircraft, it is obviously too wasteful to strike organizations that are not well equipped and operate in guerrilla areas. < / P > < p > “for maintaining the stability of the Afghan regime, it is particularly important to have air force. And helping Afghanistan to establish its air force is also a commitment made by the United States before withdrawing from Afghanistan. Compared with those expensive “heavy equipment”, cheap, durable and simple aircraft become the first choice. It not only costs less, but also has simple training, which is convenient for the Afghan army to start quickly. ” Wenchang said. At this time, the light attack aircraft jointly developed by Brazil and the United States entered the vision of the United States and Afghanistan. The U.S. military realizes that propeller aircraft not only has faster speed than modern helicopters, but also is more handy in low altitude surprise operations. It is very practical to attack terrorist organizations, guerrillas and other targets. < / P > < p > in 2013, the United States and Embraer signed a $427 million military aircraft procurement agreement to purchase 20 a-29 aircraft to help Afghanistan establish its air force. In response to this choice, a Pentagon spokesman said that the Brazilian a-29 is an all-round aircraft suitable for low-intensity operations, which is of great help to the US led establishment plan of the Afghan air force. < / P > < p > in fact, the US military has a good memory of propeller aircraft. The last propeller to ground attack aircraft, the A-1 “SKYRAIDER”, participated in the Vietnam War. On the battlefield, the A-1 is easy to maintain, low cost, and can be launched many times in a day. In recent ten years, small-scale conflict has become the most important combat form for US forces in Afghanistan. The enemy they face is good at guerrilla and harassing operations. When carrying out air to ground support operations, the US Army found that the A-10 attack aircraft was good, but the cost was too high. It was not worth the loss to use it to attack the wandering soldiers. < / P > < p > therefore, the U.S. military hopes to purchase a light attack aircraft to deal with such a combat scenario. At that time, a number of well-known aviation enterprises launched new attack aircraft to participate in the US military bidding. In December 2011, the U.S. military announced that the a-29 won the bid, and subsequently signed a US $355 million procurement agreement to purchase 120 a-29. But in 2012, the agreement was terminated for various reasons. < / P > < p > and when the United States transferred the first four a-29 to the Afghan air force, its remarkable performance made the air force again interested in this weapon. In 2017, the U.S. air force launched the oa-x light attack aircraft program, with an estimated procurement quantity of 300. As a strong competitor of this project, a-29 attracts much attention. However, the US Defense News Network reported on February 11 this year that the US Air Force has finally made it clear that it will not purchase light attack aircraft, thus ending the three-year long debate on whether to buy 300 low-cost aircraft for anti-terrorism. In this regard, Wenchang said, “after Trump came to power, the focus of US national security strategy has shifted from anti-terrorism to big power competition. The light attack aircraft project began in the period of security strategy focusing on anti-terrorism, but after turning into the competitive strategy of big countries, the light attack aircraft project is out of date. From this, we can understand the reason why the US Air Force purchased light attack aircraft such as a-29 and later cancelled the project. It can also be inferred that the U.S. Air Force will not purchase such aircraft on a large scale in the future. However, one thing is that counter-terrorism in the Middle East is still an important part of the U.S. security strategy. It is possible to purchase some of them appropriately, but the amount will not be too large. “. Due to its obvious advantages, propeller aircraft are very common in both military and civil use. For example, Russia’s TU-95 strategic bomber and an-12 transport plane, Ukraine’s an-70 transport plane, the United States’ C-130 transport aircraft and E-2 early warning aircraft are still playing a huge role. According to Wenchang, turboprop engines are used in propeller aircraft. Compared with jet aircraft, propeller aircraft has many advantages, including good low-speed performance, fuel saving, simple maintenance, good safety, and low requirements on the take-off and landing site. It is suitable for field operation and has a wide range of applications. This is also the main reason why it is difficult for the military of various countries to abandon propeller aircraft. At present, transport aircraft and special aircraft use propeller aircraft more. In addition, some UAVs also use turboprop engine, such as the MQ-9 of the US Army, which focuses on its good low-speed performance. Wenchang popular science said: “the core of propeller aircraft is turboprop engine, and its working principle is basically the same as that of turbofan engine. It can be seen as two melons on a vine. In a simple analogy, the turboprop engine can be regarded as a turbofan engine with a large bypass ratio without the bypass. ” He pointed out that the main development trend of turboprop engine in the next step is to develop from single rotor to multi rotor, the compressor from simple axial flow to axial flow + centrifugal type, the use of better high temperature materials and cooling technology to improve the temperature and gas pressure in front of turbine, and the application of digital technology and full power digital electronic control The fifth is to use a mature core aircraft to make local changes to develop a series of turboprop engines to meet the needs of different aircraft. Of course, propeller fan engine can also be developed, which combines the advantages of turboprop and turbofan engine, taking into account low-speed performance and high-speed performance. < / P > < p > “of course, the a-29 is not a” master aircraft “. In fact, it is a very modern aircraft. In addition, the avionics system is equipped with more advanced data links, airborne computers and infrared sensors. At the same time, it can also mount various weapons, including ordinary bombs, precision guided bombs, air-to-air missiles, etc. These technological advances basically represent the development direction of modern propeller aircraft Wenchang said.