03.2 - Structural Analysis and Design, Structural Dynamics, Aeroelasticity
SOLAR UAV GUST LOAD AMENDMENT
Y.-Y. Hou¹, Z.-Q. Liu¹, C. Ji¹; ¹China Academy o f Aerospace Aerodynamics , China
Loading analysis is the key technology in the process of aircraft design. For UAVs, analysis of the gust load is usually carried out by the Pratty method. But for the solar UAV flight, due to low speed, lightweight, low frequency and large deformation, the validity of Pratty method is worth discussing. rnThis paper took a certain kind of High Altitude Long Endurance (HALE) UAV as an example, briefly introduced how to calculate the structural payloads of this UAV by means of Pratty method and calculated the structural payloads of the aircraft according to the design standards of UAVs. Besides, through the method of Dynamic analysis of structure in unsteady aerodynamic force, this paper proposed that the problems existing in the calculation process of the UAV’s payload can be solved by the aforesaid standards and the error was briefly calculated and assessed. rnAnd it will be found it through this calculation?that for the general aircraft, the gust cut coefficientresults obtained from the equation are very accurate and the error is within 4%?but when the dimensionless mass below 1?the difference of the computation becomes obvious, for a given aircraft as an example, the gust load is overestimated by 17% duing to the low wing load. In addition, due to the low flying speed, gust load will be overestimated by 15%.rnThe analysis result showed that when designing this kind of UAV based on common standards, the actual structural payload was generally overrated. Based on this, we propose a new formula for calculating gust loads, calculations show that the result of the formula is lower than the result in UAV design specifications for more than 40%.Therefore, the UAV designing standards needs to be rectified based on the structural and aerodynamics characteristics of this kind of UAV.