The USAF Multivariate Accommodation Method

The USAF has been using a multivariate method for specifying pilot body size for nearly ten years. The Multivariate Accommodation software was originally written for a VMS environment using the statistical package SAS. It is now available for PC computers. The program is based on the CADRE statistical method developed by Bittner (1987), and the Anthropometric Database at the Computerized Anthropometric Research and Design Laboratory (Robinson et al., 1992), and has been very effective in increasing body size accommodation in USAF cockpit designs. The technique relies on principal component analysis which describes the variation of the original multivariate distribution with a set of orthogonal axes (principal components). Selection of the anthropometric measurements, the number of principal components used to represent the variation in their distribution, and a full understanding of the assumptions implicit in the model are all critical in generating useful representative accommodation cases. The authors will discuss previous applications of the method as well as demonstrate its limitations when used outside of cockpit/workstation designs.