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A MULTIVARIATE ANTHROPOMETRIC METHOD FOR CREW STATION DESIGN (U)

AL-TR-1993-0054

Richard S. Meindl
Jeffrey A. Hudson

Department of Anthropology and
School of Biomedical Sciences
Kent State University
Kent, Ohio

Gregory F. Zehner
Crew Systems Directorate
Human Engineering Division
Armstrong Laboratory

Wright-Patterson AFB, Ohio 45433-7022

March 1993

pp. i - viii and 1 - 33

ABSTRACT:

"Body size accommodation in USAF cockpits is still a significant problem despite all the years of experience and the many aircraft designs that have been developed. Adequate reach to controls, body clearances (particularly during escape), and vision (internal and external), are all functions of pilot body size and position in the cockpit.

One of the roots of this problem is the way cockpit accommodation is specified and tested. For many years the percentile pilot has been used. This paper describes the errors inherent in the "percentile man" approach, and presents a multivariate alternative for describing the body size variability existing in a given flying population. A number of body size "representative cases" are calculated which, when used properly in specifying, designing, and testing new aircraft, should ensure the desired level of accommodation.

The approach can be adapted to provide anthropometric descriptions of body size variability for a great many designs a=or for computer models of the human body by altering the measurements of interest and/or selecting different data sets describing the anthropometry of a user population."

INTRODUCTION:

"The recent development of computer models of the human body for describing dimensional variability of military personnel has advanced beyond current methods to describe and use available anthropometric data. In fact, anthropometric data are generally used to estimate only the extremes of univariate (single variable) distributions of a few gross dimensions, with little provision for individuals with unusual anthropometric proportions (Roebuck et al.,1975). Since extreme ratios (e.g. long buttock-knee length coupled with short sitting height) present the most difficult design problems for accommodation in workstations or for protective equipment, univariate percentile rankings for user populations are inappropriate, except for the most general description of international anthropometric variability.

Subgroup methods, which identify and select individuals atypical in combinations of two or more variables, partly address this issue. However, the severe sample truncations used in this method require initially massive data bases. This is especially true if subgroups are defined by the outermost regions of joint distributions of more than two variables.

Regression methods predict body proportions that are realistic as well as segment sizes that are additive (Robinette and McConville, 1981). These approaches require that one or two "key" dimensions be chosen as independent variables. Yet all human body measures are "free to vary" in an experimental sense, and therefore serve poorly as regressors. This problem can be particularly pronounced in those instances in which standard deviations from regression are large (or bivariate correlations are low). For example, the statistical assumptions necessary for the application of least-squares regression designs are approximated poorly in workstation dimension studies, owing to moderate intercorrelations (McConville et al., 1978), and not at all in the analysis of mask fit/seal accommodation, because the correlations among human facial measurements are extremely low. The typical results of these analyses are extreme values for the independent variables (regressors), and considerably less extreme values for the dependent variables (regressands) (those predicted)."

Additional segments include the following. 

THE MULTIVARIATE DESCRIPTION OF AN ANTHROPOMETRIC SAMPLE: METHODS

ANALYSIS OF A TWO-COMPONENT MODEL

A THREE-COMPONENT MODEL: A COMBIMAN APPLICATION

THE PROBLEM OF MULTIPLE POPULATIONS

CONCLUSION

"A preliminary attempt was made, at the conclusion of this analysis, to reduce six critical cockpit dimensions to two new measures (principal components), and to disaccommodate extreme anthropometric combinations as symmetrically as possible, while still applying the sitting height restrictions for the current population of Air Force flying personnel. It was also found appropriate to equally weight the anthropometric information of the three "derived" populations (68AF white females, 65AF black males, and 65AF white males), or to consider each population separately and combine the results. The issue of designing a workstation based on the anthropometrics of a composite user population is an important one. It requires a multivariate approach, additional survey data, and of course some reliable estimates of the actual proportions of males, females, Whites, Blacks, and others in future user populations. Depending on the extent of international application, some analysis of the anthropometrics of additional populations may also be required."

There are six Figures, 7 Tables and 10 references. 

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