Evaluation of Muscular Forces That Can be Applied to Flight Controls

Abstract

Excessive pilot flight-control forces have been identified as a causal factor in aircraft accidents, incidents, and anomalous events. However, the regulatory design requirements for fixed-wing and rotary-wing air-craft that are contained in the Code of Federal Regulations (CFR) have not been validated or updated in decades, and data for some specific situations were never included in the specifications. Results are presented for a recent study of over 300 participants categorized by gender, pilot/nonpilot status, and age group (10-year brackets from 18 through 69). Controls examined included sticks (left, center, right), yoke, rudder pedals (left, right), and helicopter collective. Results indicated that, on average, more than half of the sample could not achieve the short-term tabled forces used as reference points. However, more than half (60 to 87%) were able to sustain the prescribed long-term forces for 4 minutes or more in some control axes. It is recommended that reference tables both internal to the CFR and referenced by the CFR be modified to accommodate a larger percentage of the current user population.

Investigation into the Effects of Backrest Angle and Stick Location on Female Strength

“…Finally, Table 7 shows the comparison between the recommended value from Beringer’s (2019) study, the Code of Federal Regulations (CFR), and the results of this study. The recommended values of the CFR were two to three times greater than the strength values recommended in this study and in Beringer’s studies [ 8 , 9 ]. One of the reasons for this is that the recommended forces in the Code of Federal Regulations (CFR) were based on males’ strength.…”

“…According to previous studies, the strength in both maneuver directions (forward–backward) of the pitch and both maneuver directions (adduction–abduction) of the roll were again averaged to represent the recommended strength value [ 8 , 9 ]. Using the average strength to represent the recommended value may result in a problem whereby the strength is greater than the 5th percentile of female strength in the weaker maneuver direction of the force.…”

“…It may be a potential hazard for the pilots if the force feedback of the controller is too little or too great when they are on duty. Excessive force requirements of flight control is one of the causes of aircraft accidents and errors [ 8 , 9 ]. However, the design guideline for the recommended force only considers male strength and has not been reevaluated or updated in decades.…”

“…Beringer and colleagues recently published a study report for the Federal Aviation Administration (FAA). Beringer’s studies used 5th percentile female values as the recommended operation strength to guarantee that 95% of the population is able to operate these systems [ 8 , 9 , 10 ].…”

“…As a rule of thumb, female strength is two-thirds the strength of males [ 11 ]. In general, the percentage of female to male strength ranges from 45% to 80%, depending on the muscle groups or types of maneuvers [ 8 , 9 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. For example, the strengths of females were found to be 53% and 48% of the strength of males for pulling and pushing in sitting positions [ 14 ].…”