Chapter 14. Anthropometry and Biomechanics - FAA

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Chapter 14 Anthropometry and biomechanics HFDS 2003 (amended Oct 2009) 14.5.2.3 Comparative strength. Research has produced littleinsight into the strength of women relative to men. Thefollowing strength relationships developed by the US ArmyResearch Institute of Environmental Medicine should be useduntil better data becomes available:a. For upper extremities, females strength is 56.5% of men.b. For lower extremities, female strength is 64.2% of men.c. For trunk extremities, female strength is 66.0% of men.Explanation. These numbers may serve as a design ruleuntil more information becomes available. 14.5.2.4 Preventing tremor in positive control performance.Tremor is important in activities in which a body member ismaintained in a precise position or motion (tasks involving finecontinuous control, detailed drawing, tracking, tracing, cutting,or painting). The following features should be designed intosystems or equipment, where applicable, to help reduce tremorand ensure positive control performance of fine detailed tasks:a. ensure that visual reference can be used,b. provide support of the bod y and the member involved, forexample, the hand or arm,c. support the hand because tremo r is less if the hand is203.2 mm (8 in) above or below the heart level, andd. provide mechanical friction in the control device to addenough resistance to movement to partially counteract theenergy of the vibrations of the body member. [Source:Israelski, 1977]Definition and discussion. Tremor is the oscillation ofa body extremity which may occur along with an effort tomaintain a fixed position or direction. The degree oftremor is measured by the distance or number ofdepartures from the fixed path or position per unit oftime. Tremor increases when (1) effort is made not totremble, and (2) fatigue is present. It is greatest invertical motion, less in front-to-back motion, and least inside-to-side motion.14-46
HFDS 2003 (amended Oct 2009)Chapter 14 Anthropometry and biomechanics14.5.3 Push and pull forces14.5.3.1 Horizontal direction of force. Manual horizontal pushand pull forces that are initially necessary to set an object inmo tion , or to sustain the motion over a period of time, should notexceed the values given in Exhibit 14.5.3.1. For the second orthird person applying horizontal forces, the value in the Exhibit'sfirst co lumn should be doubled or tripled, respectively. For eachadditional person (beyond the third) another 75 percent of theforce value in the first column should be added. [Source: MIL-HDBK-759B, 1992]Explanation. The Exhibit shows maximum push andpull forces that a designer would be expected to use whenappropriate body positions, support, and tractionconditions are provided. Use of the maximum valuesshown in the Exhibit is predicated upon a suitable surfacefor force exertion (vertical with rough surfaceapproximately 400 mm (15.75 in) wide and between 0.51- 1.27 m (1.673 - 4.167 ft) above the floor) to allow forceapplication with the hands, shoulders, or back.Exhibit 14.5.3.1 Horizontalpush and pull forces that can be exerted14-47
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Chapter 14. Anthropometry and Biomechanics - FAA

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