Wing instability of a full composite aircraft

Abstract

Aeroelasticity as a phenomenon is the main source of instability for aircraft. For this reason, considering this phenomenon in design of aircraft structures is essential. From various types of instabilities, self-excitation vibration of wing or coupled bending–torsional vibration of wing and aileron called flutter is a very important phenomenon. To apply for certification for the full composite aircraft studied in this research, based on Joint Aviation Requirement (JAR-23), it must be shown that the wing of the aircraft is free from flutter. The natural frequency of bending and torsional vibration of the wing as well as that of rotation of aileron and bending of the wing must be different. To reach to these goals, a finite element software (Nisa) and an experimental modal analysis technique are used. A convergency analysis is used to verify the size, number and type of element used in the finite element modeling. Also, the results obtained from finite element analysis are compared with the results obtained from closed form solution. Torsional stiffness of the wing and the distribution of mass along the wing are calculated. In the next step, natural frequencies of bending and torsional vibration of the wing as well as that of the rotation of the aileron are calculated. Finally, based on JAR-23 standard and the results obtained from analysis it is concluded that the aircraft, in the range of design speed, is free from flutter.