Design optimization
The optimization research has primarily addressed the formulation of semi-analytical sensitivities for problem of rotorcraft interest (e.g., for the stability of system with periodic coefficients), and the multidisciplinary design optimization (MDO) of helicopters.

This paper (text and figures) is a survey of applications of design optimization to helicopters. Although the paper is a few years old, its conclusions still very much stand today.

This paper describes an MDO study in which the constraints were taken from the flight dynamics and control, aeromechanics, and rotor dynamics subdisciplines, and the design variables included rotor, airframe, and flight control system design parameters. The paper is part of Dr. Dario Fusato's Ph.D. dissertation.