Value-based multidisciplinary optimization for commercial aircraft program design

Abstract

Traditional commercial aircraft design attempts to achieve improved performance and reduced operating costs by minimizing maximum takeoff weight, but this approach (does not guarantee the financial viability of the program to the manufacturer. Improved design practices would take into account not only aircraft performance but also financial aspects of the design. The methodology suggested herein investigates multidisciplinary design optimization (MDO) involving performance and finance jointly in aircraft program design, as well as assessment of program business risk. A value-based MDO framework couples a performance model with an improved stochastic program valuation, accounting explicitly for both uncertain demand via market volatility and managerial flexibility by invoking Real Options theory. Stochastic program value is used as the new objective for the design optimization problem. The methodology and framework developed are applied to a design example for the Blended-Wing-Body aircraft concept. Value-based optimization yields a design with a 2.3%-higher program value than that of the conventional minimum-weight solution.

(cont.) Comparing performance- and value-optimized designs, it is shown that the optimizer chooses to trade aerodynamic efficiency for reduced manufacturing costs. The effects of varying the aircraft range and speed on maximum-value solutions demonstrates that incorporating value into the design process permits more fully-informed program decisions that have optimal financial impact. Sensitivity analyses quantify the impact of technical and financial uncertainty on the stochastic value due to individual program parameters, and permit insight into the relative business risk associated with each for value-optimal designs. The results show that long-term cash flows should be emphasized over development costs. Traditional, deterministic net present value is shown to be inappropriate for use as a MDO objective function. Risk is not addressed adequately through the choice of discount rate, leading the objective to drive the optimization to make poor design tradeoffs and typically resulting in trends contrary to those of the improved stochastic valuation. Value-based MDO represents a logical progression and necessary step in the continual evolution of the aircraft design process.