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ASSESSMENT OF ANTHROPOMETRIC ACCOMMODATION IN AIRCRAFT COCKPITS

Kenneth W. Kennedy, Ph.D. and Gregory F. Zehner
SAFE Journal, Vol. 25, No. 1, January, 1995.

ABSTRACT: "This paper focuses on aspects of anthropometric accommodation in aircraft cockpits and anthropometric multivariate models as accommodation criteria. Appropriate body size accommodation in aircraft cockpits is still being sought in military services despite the many years of experience logged by designers. This issue is more important than ever in today's Air Force because the demographics of the pilot population are changing. Larger pilots are currently being admitted and the probability that much smaller pilots will be in flight training in the near future is very high. For that reason, a set of evaluation procedures has been developed to assess the anthropometric accommodation limits of cockpits. Seven aspects of accommodation are examined: 1) overhead clearance, 2) operational leg clearances, 3) control stick/wheel operation clearance, 4) ejection clearances, 5) rudder pedal operation, 6) visual field, and 7) hand reach to controls."

INTRODUCTION: ". . . For many years, cockpit design was based on the concept of accommodation the 5th through 95th percentile for a limited number of critical anthropometric dimensions of the male pilot. Within the aircraft and automotive industries, this concept was inappropriately extended to larger numbers of dimensions, and eventually evolved into the "percentile man" concept in which essentially all body dimensions are included. As a result of errors inherent in this "percentile man" approach, considerable numbers of pilots have experienced difficulty operating or escaping from their aircraft. To correct these deficiencies, multivariate alternatives to the percentile approach have been developed to describe body size  variability in the USAF flying population. An attempt at partial multivariate representation was incorporated in the two-dimensional drawing board manikins developed by the USAF in the mid 1970s. . . .  A much more sophisticated and complete multivariate analysis has now been developed, again by the USAF, in which a number of body size combinations or "multivariate cases" were calculated. These not only describe "typical" small and large pilots, as the percentile approaches attempted to do, but take into account the variability of body proportions found in many individuals who are not uniformly "large" or "small." The multivariate models . . . are typical of those used by the USAF to evaluate accommodation in aircraft cockpits."

". . . In most aspects of body size accommodation - overhead and ejection clearances and vision, for example - anthropometric relationships are rather straightforward. Others are considerably more complex. The ability to reach hand controls, for example, is not only influenced by the length of the arm, but also by Sitting Eye Height, Sitting Shoulder Height, and the length of the legs. Sitting Eye Height plays a decisive role in seat adjustment, since the pilot must seek optimum vision both inside and outside the cockpit. the seat may have to be moved to a different position to obtain full control of the rudder pedals. The level of the shoulders in the cockpit, which directly influences reach capability, can thus be influenced by attempts to meet vision and rudder pedal access requirements. Finally, not only the length of the arm, but any factor that influences mobility at the shoulder and elbow, such as design, fit, and adjustment of harnesses and personal protective and survival gear, strength, and motivation come into plan in the act of reaching. It is typical behavior for a pilot to shift seat positions to achieve optimum accommodation for a variety of needs. It follows that several pilots with the same arm length can have different reach capabilities in the cockpit, depending on his/her other body dimensions. If only one subject is used in the evaluation of reach, or any other aspect of accommodation, the results will be relevant only to that individual."

USING THE DATA: ". . . There are several uses for accommodation data, the most straightforward of which is the verification of design specifications. If a cockpit is required to accommodate a given range of body sizes, these techniques make it possible to validate compliance. . . . Another use for these data is to predict the fit of a range of body sizes in a crewstation. Data can also be used to assess the effects of expanding the ranges of body sizes permitted to enter pilot training. . . ."

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