Probabilistic Manufacturing Tolerance Optimization of Damage-Tolerant Aircraft Structures Using Measured Data

Abstract

Manufacturing tolerances play an important role in designing low-cost and low-weight aircraft structures. A probabilistic cost model is developed that explicitly models performance cost along with quality and manufacturing costs to optimize manufacturing tolerances for damage-tolerant aircraft structures. The tolerance optimization is demonstrated for the design of a wing spar with fastener holes. The advantage of including performance cost is illustrated by comparing to an optimum found by ignoring the performance cost, showing substantial change in the optimum tolerance and total cost. The random aspect of quality cost is illustrated using measured manufacturing error data collected from the wing spar assemblies of a business jet. The paper also quantifies the uncertainties in the optimum due to finite samples of measured data used for modeling manufacturing error distributions, which were found to be small due to a large number of samples.