Aerospace Technic and Technology

The subject of this study is the aeroelastic stability of aircraft flight control surfaces caused by the degradation of mass-balance weights. The mass and inertia properties of control surfaces play a key role in flutter prevention and are typically controlled by balance weights installed ahead of the hinge line. In practice, however service experience shows that these weights may suffer from corrosion, material loss, or deterioration of attachment integrity during long-term operation, leading to deviations from nominal inertial characteristics. The aim of this study is to examine the aeroelastic implications of degraded mass-balance weights and to interpret their effect as a source of inertia-induced freeplay in the dynamics of aircraft control surfaces. In contrast to classical kinematic freeplay, which is associated with mechanical clearances in hinges and actuation systems, the phenomenon considered herein originates from the incomplete or intermittent inertial participation of the balancing mass. This leads to a nonlinear dynamic behavior characterized by a piecewise variation of the effective moment of inertia of the control surface. The objectives of the study include the development of a representative aeroelastic model of a control surface with piecewise inertial properties, the evaluation of its linear flutter characteristics, and the analysis of nonlinear dynamic responses associated with inertia-induced freeplay. The research methods are based on reduced-order aeroelastic modeling, linear eigenvalue flutter analysis, and nonlinear time-domain simulations. A piecewise variation of the effective moment of inertia is introduced to represent the degraded mass-balance configuration, allowing for the identification of Limit Cycle Oscillations (LCO) and subcritical instabilities. The results of the numerical investigation demonstrate that inertia-induced freeplay can lead to sustained oscillatory responses at airspeeds below the linear flutter boundary, indicating a potential aeroelastic risk that may not be detected by conventional certification-level analyses. The practical relevance of the proposed approach is illustrated using a case study based on the Embraer 505 aircraft, supported by real maintenance findings of corrosion in mass-balance weights. It is shown that the replacement of degraded weights followed by static balancing effectively restores nominal inertial properties and eliminates the identified nonlinear aeroelastic effects. The scientific novelty of the study lies in the physical interpretation of mass-balance degradation as a source of inertial freeplay and in the proposed modeling framework, which enables a simple yet effective assessment of its impact on aeroelastic stability. The obtained results contribute to a better understanding of maintenance-related aeroelastic risks and support the development of improved inspection and airworthiness assessment practices for modern aircraft.

aeroelastic stability; flight control surface; mass-balance weights; inertia-induced freeplay; Limit Cycle Oscillations; flutter; static balancing, maintenance

Bisplinghoff, R. L., Ashley, H., & Halfman, R. L. Aeroelasticity. 2nd ed. New York, Dover Publications, 1996. 860 p.

Scanlan, R. H., & Rosenbaum, R. Introduction to the Study of Aircraft Vibration and Flutter. New York, McGraw-Hill, 1951. 432 p.

Hodges, D.H., Pierce, G.A., Introduction to Structural Dynamics and Aeroelasticity, Cambridge University Press, 2011. 272 p.

Boynton, R., Wiener, K. Measuring Mass Properties of Aircraft Control Surfaces. Proceedings of the 59th Annual Conference of the Society of Allied Weight Engineers. St. Louis, Missouri, USA, 2000.

Candon M., Muscarello V., Verhagen W., Marzocca P., Levinski O. Aeroelastic response of an airfoil with structural freeplay in transonic buffeting flow. Journal of Fluids and Structures, 2026, vol. 140, Article no. 104445. DOI: 10.1016/j.jfluidstructs.2025.104445.

Yu, Q., Zhang, Y., & Wang, Y. Numerical analysis of free play-induced aeroelastic phenomena: A numerical approach with adaptive step size control. International Journal of Aerospace Engineering, 2024, vol. 2024, pp. 1–13. DOI: 10.1155/2024/9915761.

Tang, D. M., Dowell, E. H. Experimental and theoretical study of gust response for a wing–store model with freeplay. Journal of Sound and Vibration, 2006, Vol.295, pp. 659–684. DOI:10.1016/j.jsv.2006.01.024

Aircraft Maintenance Manual P/N 2757. System Description Section, Subject 27-00-00 Flight Controls,- pp. 1-16 Rev. 66, 12 Dec 2025, (In English, unpublished).

Embraer service bulletin 505-55-0004. Stabilizers - elevator, aileron and rudder mass-balance replacement, Rev.01 25 Mar, 2020. 14 p. (In English, unpublished).

Illustrated tool and equipment manual 3716. Rev.63, 02 Dec 2025 (In English, unpublished).