2014 Brazilian Air Force Anthropometric Survey and a Comparison of Anthropometric Design Requirements and Verification Methods: The Beginning of an Ergonomic Cockpit Design Solution

Introduction: Anthropometric data are essential for the design of military equipment including sizing of aircraft cockpits and personal gear. Currently, there are no anthropometric databases specific to Brazilian military personnel and as a result, the aircraftin the Brazilian Air Force (FAB) inventory were designed using U.S. military legacy databases (USAF Male 1950, USAF Male 1967, US ARMY 1988, USAF Female 1968). This contributes to aircrew accommodation problems in the FAB, including but not limited to reach problems for small pilots and lack of head clearance for tall pilots. Accurate anthropometric databases must be established in order to improve the design and efficacy of military equipment. Furthermore, there is no set protocol for delineating the way in which databases are used to establish the design parameters of the product or workstation -- its dimensions, its adjustments ranges, and its accommodation envelope. Thus, in order to clarify this gap and provide informed databases for the designer's decision, this research aimed to establish the reliability and accuracy of two such methods. The establishment of a National Anthropometric Database of FAB Pilots (Phase 1) and the methods comparison (Phase 2) have scientific and practical applications: The purpose is to create the first anthropometric database for Brazilian military personnel and to develop a method that can best estimate and define the workstation geometry and anthropometric accommodation when multiple body dimensions need to be considered.;Methods: Thirty-nine measurements relevant to the design of aircraft cockpits, protective gear, uniform sizing, and computerized digital human modeling were measured, using traditional techniques. The sample consisted of 2,339 FAB aircrew (2,133 males and 206 females) aged 16-52 years, as part of the FAB anthropometric survey. The collected data were used to create the first Anthropometric Database of the FAB. The database was instrumental in the ensuing study which determines the most effective method for establishing cockpit accommodation limits. A subset of the anthropometric data was used for the comparison of the cockpit accommodation methods. Six critical dimensions used by the FAB as /selection criteria -- sitting height; eye height, sitting; shoulder height, sitting; knee height, sitting; buttock-knee length; and functional reach -- were chosen because they drive cockpit accommodation for pilots. These data were used to compare two methods for establishing anthropometric design criteria -- Boundary Cases Multivariate and Percentile Univariate analyses.;Results: Phase 1 developed a new FAB database and compared it with U.S. Military legacy databases (USAF 1950, USAF 1967, ARMY 1988 for men, and USAF 1968 for women) and with the Brazilian general population (Air Transport Users 2008 and Industrial Workers 1988). T-Tests and F-tests revealed that Brazilian pilots were significantly (p<0.05) smaller and lighter than U.S. military personnel, and bigger and lighter than the Brazilian civilian population in most dimensions measured for both the mean and the variance. In Phase 2, the Boundary Cases Multivariate Method was better at estimating design criteria for cockpit accommodation, when compared to the Percentile Univariate Method for all accommodation envelopes used. When a 90% accommodation envelope was used as a testing limit for design criteria, 69.5% of the male population were captured using the percentile approach while 80.5% were captured using the multivariate approach; for female population, the percentile approach captured 76.7% vs. 88.4% using the multivariate approach. Similar results were obtained using the other accommodation envelopes: a 94% accommodation envelope captured 79.9% vs. 87% (males) and 85.4% vs. 90.8% (females); a 96 % accommodation envelope captured 85.4% vs. 90.6% (males) and 91.3% vs. 94.2% (females). A goodness-of-fit Chi-Square Test showed that for the male population both tested methods did not fit well into the intended accommodation range. However, the small Chi-Square goodness-of-fit values of the multivariate method showed that this method better fit to the intended accommodation envelope. Moreover, when testing the female population as well as a mixed gender population (using the limits of 5th percentile female to 95th percentile male), only the multivariate method significantly fit the expected percentage of accommodated pilots (p<0.05). In addition, McNemar's Chi-Square Test demonstrated a statistically significant difference (p<0.00001) between the ability of the multivariate approach to estimate the intended accommodation envelope compared to the percentile approach. The bivariate graph analyses showed that the multivariate approach incorporates greater extremes in body sizes or unusual body dimension combinations, while the percentile approach captured very few of the people located at the extremes.;Discussion: The FAB pilot database (2014) is the only reliable resource for designing aviator uniforms, equipment, and workstations to appropriately accommodate Brazilian pilots. U.S. Military legacy databases, as well as Brazilian civilian population databases, are not appropriate to use when designing for Brazilian pilots since measurements across these populations were found to differ significantly in several critical cockpit design dimensions. This finding reinforces the necessity for specific databases targeted to the intended user population, in order to develop optimal, customized designs. The multivariate approach was more precise and inclusive in estimating cockpit accommodation envelopes, especially when using a mixed gender sample (treating genders separately in statistical analyses but combining the results into design criteria based on both). Thus, this method should be preferred for cockpit design. This comparison is important given the lack of consensus over which method can better estimate and define the workstation dimensions and anthropometric accommodation when multiple body dimensions have to be considered. The results of this study have numerous implications for the FAB concerning the development and/or acquisition of new aircraft, upgrading existing aircraft, and the design and sizing of uniforms and protective equipment worn by aircrews.