# Design and Verification of a Large-Scaled Flapping-Wing Aircraft Named \"Cloud Owl\"
## 1 Introduction  
Prior to recently, the majority of research on flapping-wing aircraft was concentrated in the area of small and micro-planes. Micro flapping wing vehicles can function in small locations and have excellent flying efficiency, but their short endurance and low payload capacity are their main drawbacks [1; 2]. The large-scale bionic flapping-wing aircraft may thus satisfy the needs of long-range, long-endurance flight as well as high-efficiency, low-speed cruise flight. Several large-wing flapping-wing aircraft are shown in Figure 1. The Smart-bird [3; 4] has a wingspan of 2 m, a weight of 0.48 kg, a flight speed of 5 m/s, and a flapping frequency of 2 Hz; however, even though it has good low-speed flight stability and gliding performance, its load-carrying capacity and endurance are currently unknown. The \"Robo raven\" [5; 6] has a wingspan of 1.168 m, a weight of 290.3 g, a flight speed of about 6.7 m/s, and a flapping frequency of 4 Hz; the falcon [7] has a wingspan of 1.2 m, a total weight of 600 g, a flight speed of 8 m/s, a flapping frequency of 3.5 Hz, and can carry a total weight of 16.7% of the payload for a 20-min flight. The \"HIT-Hawk\" and the \"Hit-phoneix\" [8; 9; 10] had wingspans of 2.0 m and 2.3 m, weights of 792 g and 675 g, respectively, and maximum take-off weights of 1.15 kg and 0.86 kg, respectively, with no-load maximum stable flight endurances of 65 min and 8 min, respectively. By comparing the performance parameters of large wingspan (>1 m) aircraft both at home and abroad, the longest non-load flight endurance is 65 min, the flight endurance is shorter when carrying a payload, the fastest flight speed is 8 m/s, and most aircraft cannot perform autonomous flights. From a practical standpoint, there is still a significantgap [11; 12; 13]. The large-winged bionic aircraft still has much room for growth in terms of payload capacity, flight endurance, and flight speed. In this article, a flapping-wing aircraft called \"Cloud Owl\" is designed in response to the above challenges. The flapping-wing aircraft has the following features: high payload capacity, long endurance, complete electronic equipment, autonomous flight, optimization for the plateau environment, and the capability of performing a variety of flight missions. As an aircraft platform, it can satisfy the following requirements: (1) It can carry out remote control flight and autonomous flight and has onboard information perception and real-time mission planning capabilities; (2) high payload capacity, The total weight of the no-load is 980 g, and it can carry a payload of 320 g, which is enough to carry equipment such as a three-light pod, a mapping camera, a panning camera, and so on. (3) Long endurance capability: the longest endurance without payload is up to 154 min, and the longest range can reach 60 km while speed is between 6 m/s and 8 m/s. (4) High-altitude adaptability: Flapping wings are designed to be very adaptable to high-altitude conditions. After flight testing, the Cloud Owl can still fly effectively at 4500 m above sea level. (5) High dependability: The flapping mechanism has undergone more than 200 iterations and improvements, and it has an onboard flying life of more than 400 min. The basic parameters are shown in Table 1.  
This article also provides a novel design method for a flapping-wing vehicle with a large wingspan, which is verified by the prototype test. The technical advancement is in (A) The preliminary estimation of the overall parameters can be done using the biological scale of flight and the parameter correction approach suggested in this article. (B) Adaptive optimization method for flapping-wing at high altitude to provide a reference for flapping-wing design at high altitude; (C) Dependability growth test for flapping mechanism can extend the life effectively; (D) Following flight testing and system debugging, integrated flight control improvement was made to finish the design of a stab