Early the next morning, Professor Wang informed Li Tangshan to go to the main teaching building, and the vehicle that connected him to the competition had arrived.

Li Tangshan simply tidied up, and soon pulled his suitcase to the main teaching building. Professor Wang explained the driver of the pick-up and drop-off, and then took Li Tangshan out of Beihang, and Li Tangshan vaguely knew that the car was out of Beijing City, that is, to Xishan.

Li Tangshan has been in Beijing for so long, but he also doesn't have time to visit Beijing.

The car soon arrived at its destination, which turned out to be a small building next to Xishan Military Airport. The driver communicated with the reception staff of Xiaolou, and pointed to Li Tangshan. Then I drove away. The receptionist asked Li Tangshan to sign in, and the receptionist told Li Tangshan: After a month of continuous primary selection and expert recommendation, Xie Shiliu from Tsinghua University, Cao Yan from Kazakhstan Military Industry, Hong Tiejun from National Defense University of Science and Technology, Huang Fuxing of the Chinese Academy of Sciences, and Li Tangshan of Beihang University finally entered the list of semi-finals. The notice of this selection stipulates that after two days, the format of open competition will be adopted. One of them will be selected from among them to enter the 507 Institute to participate in Qian Xuesen's temporary group.

The reception staff arranged Li Tangshan's food and lodging, and also issued a note on the selection of notes.

The day after tomorrow, the relevant players were sent to the assessment point of Beijing Xishan Airport.

Historically, the West Mountain is a very good scenic spot. Beijing West Mountain is a branch of Taihang Mountain, called "the head of Taihang Mountain" in ancient times, and Beijing also called it Xiaoqingliang Mountain. Xishan is like a python, stretching out from the west and guarding the city of Beijing like an arm, also called "the right arm of Shenjing". The West Mountain is the remaining vein at the north end of the Taihang Mountain, the peaks and ridges are extended, there are several districts and counties of Fangshan, Mentougou, Shijingshan, Changping, the Yongding River called the Wuding River in ancient times runs through it, and the West Mountain is cut into two sections in the north and south. It can be seen that Xishan's status in Beijing, and Xishan Airport is on the plain at the foot of Xishan Mountain.

There are many famous mountains and historic sites in Xishan, such as Cuiwei Mountain, Pingpo Mountain, Lushi Mountain, Xiangshan Mountain, and Xishan Yumai Lotus Leaf Mountain, Weng Mountain, etc., which are relatively close to Beijing. For hundreds of years, I don't know how many literati and scholars have been overwhelmed by the scenery of its four seasons, and they have enjoyed it; Or leave an inscription for it to add brilliance to the victory. The poet Chen Zhisui said in "Xia Qi Xishan": "Temporarily do not go to the heart, the West Mountain is a forest." The dead roots drip the spring, and the young butterflies hug the flowers and sink. The cicadas are lazy at noon, and the shade of the garden is deep. If the white clouds are intentional, wear bamboo and sing. ”

Although the West Mountain is beautiful, Li Tangshan and these players are not in the mood to come to the mountains and rivers. This tournament is a great opportunity for them, and each of them will not give up this good opportunity easily. Because the selection rules are simple and cruel, the last person left in the competition is the one who is qualified to be selected.

The opening ceremony of the selection was held in a small meeting, and after the leaders habitually talked at length about the importance of this selection and the cliché emphasis on organizational discipline, the real assessment was about to begin.

"For the first assessment, a few of you will send one of you to draw questions..."The examiner shouted in a loud voice: "The rule is very simple, the last place is eliminated, and the four who remain are the winners."

Li Tangshan from Beihang University, Cao Yan from Kazakhstan Military Industry, Hong Tiejun from the National Defense Science and Technology University, Huang Fuxing of the Chinese Academy of Sciences, and Xie Shiliu from the Qing University discussed and decided to use the most traditional and simple scissors stone cloth to decide who would draw the question.

In the end, Cao Yan, from Kazakhstan's military industry, was selected as a representative to go to the stage to draw questions. Cao Yan brought back an envelope and opened it in front of everyone. The topic is to assemble a vertical take-off and landing drone, which can independently plan the flight path and drop 10KG of materials at the target point of 200 kilometers and come back. On the first day, the second and a half days were spent reviewing the principle and assembling test flights, and the third day was carried out in the afternoon, and the assembly site was in the aircraft repair shop. The top four remained, and the fifth was out.

Li Tangshan felt that the situation was not good when he saw the topic, although he was a student of Beihang University, his major was communication. usually follows Xu Xingning and mixes with the UAV classmates who are also in the Weimin Building, but in fact, he also knows little about UAVs. Cao Yan of Kazakhstan's military industry, Hong Tiejun of the National Defense Science and Technology University, and Huang Fuxing of the Chinese Academy of Sciences seem to be full of confidence, and Xie Shiliu and Li Tangshan from Qing University are also dumbfounded when they are biased towards basic research. It seems that their luck is not too good, the first question is a field that the two of them are not very familiar with, and the eliminated should be produced between the two of them.

In fact, the expert group that came up with the question has studied their situation and came up with 5 questions, all of which are majors that they usually relate, mainly to test their ability to learn independently and solve difficulties in the face of difficulties.

As soon as everyone received the task, they immediately moved. Collect the required materials from the material support department. There are two open source flight controllers, 6 groups of power systems, one ground station, two racks, several servos, auxiliary wires, etc.

Li Tangshan and Xu Xingning are also very clear about the basic theory of drones when they fool around with the UAV department, but in reality, it is not so simple to get a drone. The main thing is that it is an electric drone, and if it is a gasoline drone, Li Tangshan can be directly out. Drones involve experience and knowledge in all aspects.

"If you have difficulties, find Du Niang" Li Tangshan thought that his classmate Xu Xingning often said a word.

Li Tangshan quickly went to the Internet to find relevant information, there are a bunch of tutorials about quadrotor assembly, but there are very few materials about vertical take-off and landing drones, most of the stickers are very principled, I Li Tangshan knows that the analysis is wrong, and it can be seen that most of the enthusiasts on the Internet belong to the DIY level. Li Tangshan had to analyze the characteristics of multi-rotor UAVs and fixed-wing UAVs by himself, and see how to match them according to their characteristics?

Li Tangshan thought that we should start from the advantages and disadvantages of two UAVs, multi-rotor UAVs are not affected by the advantages of site restrictions, hovering, low cost, etc., and the growth of models and numbers is too fast and too miscellaneous, but subject to factors such as power and aerodynamic layout, multi-rotors are difficult to meet the needs of Li Tangshan's more and more stringent assessment in terms of range, speed, flight time, etc. Although fixed-wing UAVs have a long endurance and high speed, they need a take-off runway, which greatly restricts their availability.

"That's right! The advantages and disadvantages of multi-rotor drones and fixed-wing drones happen to be complementary. Li Tangshan patted his thigh and said to himself. Li Tangshan felt that finding a way from this side should not be far from solving the problem. If an integrated technology that can take off and land vertically while ensuring high speed and long endurance is sought, it is possible to make VTOL fixed-wing UAVs.

Li Tangshan followed this direction, and a flash of inspiration appeared in his brain, Li Tangshan suddenly had an idea in his heart, can it become a vertical take-off and landing drone with a fixed wing and a quadrotor? Li Tangshan put his idea to a simulation test in MATHLAB, and the simulation test was passed, but the energy consumption ratio was too poor.

"I'm such a fucking genius!" Li Tangshan happily praised himself, in fact, this is also the only knowledge that Li Tangshan currently has about UAVs, and he can use the composite wing vertical take-off and landing scheme.