The feasibility of a composite tailored wing for a high-speed civil tiltrotor is addressed using existing analytical methods. Composite tailoring is utilized to increase the proprotor aeroelastic stability margins for a thin wing (18% t/c) designed to improve high speed performance and productivity. Structural tailoring concepts are applied to the wing alone to improve the stability of the symmetric wing beamwise bending mode and the symmetric wing chordwise bending mode, which are the two most critical modes of instability. Skin laminate tailoring is shown to favorably influence the wing pitch/bending coupling and improve the stability of the wing beamwise mode. The wing chordwise mode stability is reduced by skin laminate tailoring due to a decrease in wing stiffness, but by tailoring the distribution of stringer and spar cap areas, the wing chord mode stability can be recovered. Parametric studies show that the overall stability gains from composite tailoring can be limited because of conflicting structural design requirements imposed by the two critical modes of instability, and the necessity to balance the stability boundaries for both modes. The parametric studies are used to define an 18% t/c tailored wing configuration that meets the stability goals with a minimum weight penalty.

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An algorithm for the estimation of the natural frequency and the damping factor of lightly damped structural modes is described. The core of the identification process is a subspace-based Deterministic-Stochastic Realization Algorithm (DSRA) [l]. Identification focuses on one resonant mode at a time; this allows for filtering out the noise and harmonic components present in the data before the identification is carried out. A test to determine the reliability of the estimates is carried out so that particularly noisy records are detected and discarded. The algorithm was applied to simulated data as well as to V-22 tiltrotor aircraft flight test data obtained from Bell Helicopter Textron, Inc. and the results were compared with those obtained using the standard Prony analysis. It was found that both the Prony's method and the current algorithm performed well for most data records.