Publication: Preliminary design of long endurance uav
Date
2009-03-01
Authors
Tang, Sing Peng
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Abstract
Currently, the longest flight endurance achieved by Malaysian made UAV‟s is no longer than 8 hours. The focus of this project is to research a new UAV design capable of achieving more than 10 hours of unmanned flight with a maximum take-off weight of 40 kg at a cruising speed of 120 km/h and altitude of 1000 m. In addition, the UAV should have a take-off distance of about 150 m and landing distance of about 200 m. To define the UAV configuration, a method as described by Roskam was used in the form of aircraft design software called AAA software together with the use of other additional software like DATCOM, XFOIL and others along the design process.
The design process starts with an initial weight sizing in terms of payload system, empty weight and fuel weight. With this the maximum take-off weight was found and through the use of AAA software it was possible to define a suitable power loading (W/P) and wing loading (W/S). These two parameters are important since it will allow one to proceed to the other steps of the design process, namely airfoil selection & wing sizing, and engine selection. From the power loading selected, the required horsepower is defined and the suitable engine was researched from the market. With the observation of various types of airfoils, it was found that the NASA LS 0413 was the most suitable airfoil to fulfill the requirements of the UAV‟s design lift coefficient.
Fuselage sizing was then carried out by considering the fuselage size to ensure the required payload and fuel tanks are accommodated. Wing body sizing is then carried out by combining the wing and fuselage and ensuring the design lift coefficient is met. Next, the horizontal tail design was established with the NACA 0012 airfoil. Wing-body-tail analysis was then carried out using DATCOM to find the best position of the wing and horizontal tail with respect to fuselage.
After meeting the requirements, sizing of the vertical tail was determined according to recommended tail volume ratio. Roskam‟s analytical approach was used to generate the aerodynamic data needed for twin vertical tails since DATCOM is unable to accomplish this task. The landing gear selection, layout and its tire sizing was carried out according to Raymer‟s approach. The vertical tail, tail boom, and landing gear, influence only the drag coefficient without any effect on lift and moment coefficient; thus the full UAV clean configuration is generated by adding their drag coefficient into previous wing-body-tail data.
To increase the lift coefficient for takeoff and landing, the high lift devices are then designed. The deflection of the flaps influences the moment coefficient of the UAV.
As a result, the UAV becomes untrimmable, thus requiring control devices such as elevators. Flap deflection and elevator deflection will be studied here.
Lastly, an aerodynamic analysis, longitudinal stability analysis and performance analysis was done on the full UAV configuration to check if the design requirements are met. The results show that the main objective to fly at least 10 hours is achieved as the UAV can fly for 26 hours at constant 1000 m altitude with constant speed of 120 km/hr. The designed UAV is then drawn in CATIA V5 software.