BACK TO CONTENTS

 

CONTACT

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, the techniques described here make it possible to validate compliance.  This is done by comparing the anthropometric dimensions in the specification to the results of the evaluations.  Test subjects who are close to the body size requirements set forth in the specification can be selected.  In that way, the acceptability of proposed clearance, vision,  reach, and operability can be observed directly as opposed to being inferred.  For reach to  controls it is important to have a list of the critical controls which  must be reached in under Zone 1 restraint and those under Zone 2 restraint.  These lists should be compiled by the System Program Office and test pilots since its composition will vary depending on the aircraft's mission requirements.

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.  

(The following is from  Zehner, G.F. and J.A. Hudson, Body Size Accommodation in USAF Aircraft, AFRL-HE-WP-TR-2002-0118, United States Air Force Research Laboratory, Human Effectiveness Directorate, Wright-Patterson AFB, OH.and contributed by the authors.) "Software has been written and distributed which accepts input of an individual's anthropometric dimensions and gives [an] output of all aircraft in which that individual is accommodated. In the event that this document must be used for the same purpose, the procedure is as follows: First, small candidates must be measured for Sitting Eye Height, Shoulder Height Sitting (Acromion), Buttock-Knee Length, Knee Height Sitting, and Arm Span. First, compare the Sitting Eye Height measurements with the data in Table 3.2. If the candidate's Sitting Eye Height is less than 29.6 inches, this individual will not have adequate external vision in the T-38 or T-1. There would be no follow-on Trainer for this individual to fly. However, given the variability in anthropometric measurements, and the variability due to posture in the cockpit accommodation measurements, those who are close to 29.6 inches for Sitting Eye Height may be classified as marginal and given a "fit-check" in those aircraft. If the Sitting Eye height is greater than 29.6 inches, then it is important to calculate the amount greater and apply the adjustment listed in column three of Table 3.2. If for example, the candidate has a Sitting Eye Height of 30 inches, that value is 2.5 inches greater than the minimum requirement for the T-37. Since that seat adjusts in 0.625-inch notches, the candidate could lower the seat 4 notches and still see the minimum vision requirement. This will place the candidate much closer to rudders and hand controls. However, the candidate is only 0.4 inches larger than the minimum requirement in the T-1. The seat in this aircraft adjusts in 0.8-inch intervals. Therefore the candidate must remain in the full-up seat position for rudder and reach calculations. Those aircraft listed as 1/1 in Table 3.2 are continuously adjustable, so any amount of excess Sitting Eye Height can be subtracted directly from the seat position. At that point, classify the candidates as pass/fail (and possibly marginal) for each aircraft in Table 3.2. Next, using the seat position data, classify the candidate in each aircraft for reach to rudders using Table 4.2. The minimum Comboleg required for reaching full rudders from the full-up seat position is 40.5 inches. However, (using our candidate with a 30-inch Sitting Eye Height as an example) this person could sit 4 notches down, the minimum Comboleg from this position would be 39.5 inches. The last step is to again apply the seat position information, this time to Table 5.3 arm reach to controls. We will assume our candidate pilot has an arm Span of 63 inches and a Shoulder Height [Sitting] of 22 inches. The most restrictive reach requirement in [the] T-37 is full-forward stick with locked harness inertial reels. The equation for calculating miss distance to this control is miss distance = (.38603 X Shoulder Height Sitting (22 inches)) - (.70890 X Arm Span (63 inches)) + 34.4 inches. This equals -1.77 inches. A negative miss distance means the candidate went beyond the control by 1.77 inches and is a pass.* In addition, since the seat could be lowered 4 notches, the candidate would be 0.28 X 4 = 1.12 inches closer to the control. The final excess reach capability would be -2.89 inches. Once again it must be pointed out that there is variability (called statistical error) in this process and the numbers are best estimates. Those close to the minimum limits could be characterized as marginal and given live fit-tests.

Large pilots must be measured for Sitting Height and Buttock-Knee Length . . .  . Seat effect is irrelevant because the seat will travel up the rails during ejection, and we assume that if a candidate has overhead clearance problems the seat will have been adjusted full-down. Table 7.2 and Table 8.1 can be used directly. The same variability caveat applies to large candidates. Those very close to these limits could be classified as marginal and given a fit-check." 

* The convention would be to consider a "plus" value as one greater than that necessary to reach a given control. Multiplying the result by (-1) would satisfy this convention.

We have only limited ability to predict the individual's level of accommodation.  This is true of all measures but especially hand reaches to controls.  When regression equations are used, they must be based on large samples.  Such predictions produce "average" values expected for a population of individuals of that body size. There can be a good deal of variation around the average.  If examination indicates some question regarding an individual's ability to safely operate the aircraft, a trial in the cockpit may be warranted.

 

BACK TO CONTENTS