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The assessment of the service durability of aerospace components and assemblies has become an important segment of design. In order to meet strict safety requirements, a number of complex and long experiments are carried out. The use of finite element method (FEM) and extended finite element method (XFEM) for the estimation of fatigue life and fatigue crack growth predictions has been proved as a good alternative to the expensive experimental methods. In this paper, both experimental and numerical analyses of 2024-T3 aluminum spar of a light aircraft under variable amplitude loading are presented. FEM has been used for estimation of the spar life to crack initiation, whereas XFEM has been used for fatigue crack growth predictions and fatigue life estimation of damaged spar. The values of stress intensity factors were extracted from the XFEM solution in MorfeoCrack for Abaqus software.

In this paper the design, fabrication and analysis of behavior by full-scale verification testing for the tail rotor blade of composite laminated materials for a heavy transport helicopter is given. The verification test program for the tail rotor blade encompassed static and dynamic testing. The static tests of the blade involved experimental evaluation of torsional and flexional blade stiffness and its elastic axis position. Dynamic tests involved testing of vibratory characteristics and testing of blade fatigue characteristic. In structural vibration tests natural frequency, vibration modes and damping ratio for the structure were measured. The fatigue analysis of the structure of blade root section was performed after fatigue test cycles for detection of laminate separation, tolerance and distortion of crossections of structure.

A survey of physical and mathematically properties of various types of wind tunnel walls is given in this paper. The present paper discusses some newer developments, but concentrates mainly on the specification of wall boundary conditions that are of importance for the calculation of wall interference.

In this paper a theoretical study of the turn maneuver of an agricultural aircraft is presented. The maneuver with changeably altitude is analyzed. The effect of load factors on the turn maneuver characteristics during the field-treating flights are analyzed. The mathematical model which describes the procedure of the correct climb and descent turn maneuver are used. For a typical agricultural aircraft numerical results and limitations of the climb, horizontal and descent turn maneuver are given. The problem of climb turning flight is described with the system of differential equations which describe the influence of normal and tangential load factors on derivation velocity, the path angle in the vertical plane and the rate of turn in function of the bank angle during turning flight. The system of differential equations of motion are solved on a personal computer with Runge-Kutta-Merson numerical method. Some results of this calculation in this paper are presented.

In this paper, experimental results of wind tunnel easurements for conventional, symmetrical airfoil NACA 0012 obtained from the trisonic wind tunnel of Aeronautical Institute VTI Zarkovo, Belgrade are presented. The measurements of lift coefficient and lift-curve slope are presented. The results were obtained from tests and integrations of surface static-pressure data over a model of the NACA 0012 airfoil section. Data for the NACA 0012 airfoil were obtained for a free-stream Mach number range of 0.25−0.8 and a chord Reynolds number range of 2×106 to 25×106. The essential results of these measurements along with the results from other authors are presented and evaluated. The principal factors which influence the accuracy of two-dimensional wind tunnel test results are analyzed. The influences of Reynolds number, Mach number and wall interference with reference to solid and flow blockage (blockage of wake) as well as the influence of side-wall boundary layer control are analyzed.

This paper presents the analysis of the survivability of a heavy transport helicopter tail rotor blade made of composite laminated materials after ballistic damage made by the bullet of 7.9 mm calibre shoulder weapons. Penetrating damages made in the root part of the tail rotor blade spar have been analyzed. The test program for the tail rotor helicopter blades has included dynamic testing nondamaged and damaged blades in full-scale. Based on the results of vibratory testing and fatigue testing an assessment is made about the vulnerability and the survivability of the helicopter tail rotor blade after ballistic damage made by the bullet of shoulder weapons.