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THE DERIVATION OF LOW PROFILE AND VARIABLE COCKPIT GEOMETRIES TO ACHIEVE 1ST TO 99TH PERCENTILE ACCOMMODATION

Kenneth W. Kennedy
AAMRL-TR-86-016
Harry G. Armstrong Aerospace Medical Research Laboratory
Wright-Patterson AFB, Ohio 45433-6573
March 1986

ABSTRACT: "This study was undertaken to serve three objectives: (1) to derive new cockpit geometries in which the techniques of vertical aircraft ejection seat adjustment move the small pilot toward his/her controls and the large pilot away from them, thus avoiding the incompatibilities associated with adjusting the small pilot up and aft, away from hand controls, and the large pilot down and forward, toward hand controls [the situation found in most high performance aircraft]; (2) to demonstrate the relative ease with which the engineer can accommodate to the 1st to 99th percentile range of male body sizes within the USAF, including reach capability; and (3) to demonstrate appropriate techniques in using the AAMRL Drawing Board Manikins in the derivation of basic geometries of ejection seats and of cockpits. Design requirements are: (1) vertical seat adjustment should be for the purpose of bringing the pilot's eyes to a 15 degree Down Vision Line; and (2) all pilots within the anthropometric design range should be able to avoid thrusting their knees forward of the Ejection Clearance Line by assuming the correct ejection posture, even though they might have adjusted the seat to a considerably different position than recommended for their body size. Low Profile and Variable Cockpit Geometries are derived in detailed step by step demonstrations."

PREFACE: ". . . This paper was presented as part of the Symposium of the 26th meeting of the Air Standardization Coordinating Committee (ASCC), Working Parting 61, 'Aerospace Medical and Life Support Systems,' 5 November 1985, at the RAF Institute of Aviation Medicine, Farnborough, Hant, England. It also appears in the Report of that meeting, Volume IV, 'Symposium Proceedings.'"

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"The 1st to 99th percentile ranges of body sizes to be accommodated are listed below. This is a typical example of the manner in which anthropometric percentile range accommodation is best applied to design. The 1st to 99th percentile accommodation range is applied only to the key dimension(s).

     Eye Height, Sitting                     1st to 99th Percentile
     Thumb-Tip Reach                      1st Percentile to Top of Range
     Buttock-Knee Length                Bottom of Range to 99th Percentile
     Buttock-Popliteal Length         1st Percentile to Top of Range
     Knee Height, Sitting                   1st Percentile to Top of Range
     Popliteal Height, Sitting             1st Percentile to Top of Range
     Bideltoid Breadth                        Bottom of Range to 99th Percentile
     Hip Breadth, Sitting                    Bottom of Range to 99th Percentile

First and 99th percentile limits are specified only for Eye Height, Sitting . . . This dimension plays a decisive role in determining vertical seat adjustment range and, therefore, the total depth of the cockpit. Contrary to the apparent belief in may airframe companies and military agencies, Sitting Height is not the most critical body dimension in cockpit layout, since it is taken into account by the military services' convention in calling for a 9- to 13-inch arc originating at the Design Eye Position and to which the underside of the canopy or overhead fuselage must be tangent."

THE LOW PROFILE COCKPIT GEOMETRY

"The impetus for developing the Low Profile Geometry can be traced to conversations with members of the original cadre established at Wright-Patterson Air Force Base, Ohio, to initiate studies leading to what is now known as the Advanced Tactical Fighter (ATF). Drawing on these conversations, as well as from lessons learned in the AAMRL Hight Acceleration Cockpit (HAC) experience and from work done by the author, a basic low profile geometry was developed. It was driven by the following design requirements . . .It was specified . . . that the frontal area of the fuselage of a low profile aircraft be . . . approximately 80 percent of that of the F-16A. . . . A seated posture must be produced that would passively resist submarining during ejection, but would not result in the pilot's knees encroaching on the 15 degree Down Vision Line."

The Low Profile Cockpit Geometry is offered as a potential solution to the accommodation of a large range of body sizes in the reduced aircraft frontal area. 

Low Profile Cockpit Geometry

 

THE VARIABLE COCKPIT GEOMETRY

"Unfortunately, ejection seat design technology has been such that we have been required to accept what is, in the Human Factors sense, an unacceptable characteristic of ejection seats: namely, the adjustment of the smaller pilot up and aft, away from his controls, and the larger pilot down and forward, toward his controls." 

The Variable Cockpit Geometry offers a solution to this incongruity. 

Variable Cockpit Geometry

 

The author discusses the development of the Low Profile and Variable Cockpit Geometries as well as mockups to demonstrate the viability of each. 

 

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