The purpose of this paper is to investigate the determination of loads in the case of an unconventional unmanned aerial vehicle (UAV) design. This study was conducted for a small tailless UAV. Load limits were defined through flight simulations and compared with the envelope obtained from regulations. The analyses presented in this paper are restricted to the longitudinal motion, which is controlled by elevons.
Aerodynamic analyses were carried out with the use of MGAERO. The obtained characteristics were used to create the simulation model. The UAV simulations were performed with the use of a simulation and dynamic stability analysis (SDSA) package and MATLAB Simulink. SDSA can simulate the aircraft as a rigid body with 6 degrees of freedom, including response to the control. To collect the data, several manoeuvres were tested, each of which was commanded by a step or doublet elevons deflection. In the case of the gust loads, the “1-cos” wind shape model was assumed. EASA certification specification regulations were used in analytical loads estimation.
The results revealed that in the case of the tailless UAV, the approach based on the EASA certification specification regulations generally leads to overestimation of the maximum loads. Both manoeuvres and gust loads obtained through the simulations were lower than ones obtained by the analytical method. Moreover, in the case of the tailless aircraft, a preliminary value of the moment of inertia is sufficient to define the loads with a reasonable error margin.
This paper shows results that can be useful in the case of designing a fast unconventional UAV. The guidance regarding modification of the CS regulations is provided, which can help to avoid overestimation of loads. Applications of a simulation tool were demonstrated.
