Volume I, Section 9
9 WORKSTATIONS
{A} For a description of the notations, see Acceleration
Regimes.
This section contains the following information:
9.1 Introduction
9.2 Workstation Layout
9.3 Controls
9.4 Displays
9.5 Labeling and Coding
9.6 User-Computer Interaction Design Considerations
See the video
clips associated with this section.
9.1 INTRODUCTION
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This section presents considerations and requirements for the design of workstations.
The topics covered are workstation layout, controls, displays,
labeling and coding, and user/computer interface.
9.2 WORKSTATION LAYOUT
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9.2.1 Introduction
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This section on workstation layout covers the following areas: general workstation design factors, control/display placement and integration, human/workstation configuration, and specialized workstation requirements.
9.2.2 General Workstation Design Factors
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9.2.2.1 General Workstation Design Considerations
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9.2.2.1.1 Human/Machine Task Division Design Considerations
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Some workstation interactions will be complex, involving many subtasks. The designer must determine how the performance of these subtasks will be divided between humans and machines. The goal is to achieve the most effective overall system, making best use of the different capabilities of humans and machines. In making this decision, the following factors should be considered.
a. Functional analysis of the subtasks.
b. Human capabilities and cognitive load limitations.
c. Machine capabilities.
d. Human/machine integration capabilities.
e. Task analysis to ensure smooth integration of human and machine functions.
9.2.2.1.2 Generic Workstation Design Considerations
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Design considerations for generic workstations are presented below.
a. Interchangeable Components - Workstations should be designed to incorporate interchangeable components and common interfaces to the greatest extent practical.
b. Reconfigurable workstations - Workstations should be capable of being reconfigured to accommodate as wide a variety of uses as practical.
9.2.2.1.3 Layout Design Considerations
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Workstation configurations should take into account the operator's needs and capabilities, physical dimensions and the viewing angles and distances.
9.2.2.2 General Workstation Design Requirements
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9.2.2.2.1 Workstation Illumination Design Requirements
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Requirements pertaining to workstation illumination in Paragraph
8.13.3.6.
9.2.2.2.2 Congestion and Interference Design Requirements
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Design requirements pertaining to workstation congestion and distractions are presented below.
a. Traffic - Workstations shall be located so as to minimize interference with and from traffic areas.
b. Distractions - Workstations shall be designed such that all external distracting stimuli to the operator are minimized.
9.2.2.2.3 Orientation Design Requirements
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Workstations shall be designed around a specific orientation . Unless specific applications dictate otherwise, this orientation shall be consistent with that of the surrounding area.
9.2.2.2.4 Workstation Color Design Requirements
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Workstation color selection requirements are specified below.
(Refer to Paragraph 9.5.3.2 i, Color Coding, for related information.)
a. Color Selection - Neutral colors shall be used in workstations.
b. Reflections - Workstation surface colors shall be lusterless.
c. Controls:
1. Controls shall be black or gray unless special functions dictate otherwise (e.g., emergency evacuation controls are striped black and yellow).
2. Toggle switch handles shall have a satin metallic finish.
3. Control colors shall provide good contrast between controls and background.
d. Panel Color Finish - The panel color shall provide good contrast between the labels and background. Label/background colors shall be consistent within a functional area.
e. Consoles and Pedestals - The color of structural members of control consoles and pedestals and overhead mountings for control units shall be consistent with surrounding areas.
f. Meter Bezels - The meter bezels shall be the same color specified for the particular panel on which the meter will be used.
9.2.2.2.5 Workstation Ventilation
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Workstations with complete or partial hoods shall be designed as follows in accordance with the requirements given in
Paragraphs 5.1.3 and 5.8.3.
a. Ventilation shall be provided.
b. Air returned to the habitable area shall not contaminate the atmosphere, consistent with NHB 8060.1.
c. The air stream flow rate and direction shall be adjustable by the workstation operator.
9.2.2.2.6 Standardization
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The workstation design shall standardize common features and functions from element to element to enhance performance and safety and to minimize training requirements.
9.2.3 Control/Display Placement and Integration
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9.2.3.1 Control/Display Placement and Integration Design Considerations
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The placement and integration of controls and displays should optimize user performance and task accomplishment. Control/display placement should be consistent and logical to the user with respect to the tasks to be performed.
9.2.3.2 Control/Display Placement and Integration Design Requirements
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9.2.3.2.1 Control Spacing Design Requirements
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Requirements for control spacing are provided below.
a. Normal Spacing - Minimum and preferred spacing for different types of controls (for the ungloved condition) shall be shown in
Figure 9.2.3.2.1-1.
b. Gloved Operation - All space modules shall have those controls necessary for maintenance and recovery following a depressurization (e.g., as a result of a micro-meteoroid hit), operable by a pressure-suited crewmember.
(Refer to Paragraph 14.4.3.2, EVA Control and Display Design Requirements, for specific requirements.)
c. Miniature controls - Spacing of miniature controls, intended for ungloved hand operation, shall maintain the same clearance footprint about each control (i.e., the edge-to-edge separation between the pair of controls located on either side of a third control) as indicated in
Figure 9.2.3.2.1-1.
Figure 9.2.3.2.1-1 Control
Spacing Requirements for Ungloved Operation
Reference: 1, p. 4.9-9, NASA-STD-3000 256
9.2.3.2.2 Display Readability Design Requirements
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Displays shall be located and designed so that they may be read, to the degree of accuracy required, by personnel in the normal operating or servicing positions without requiring the operator to assume an uncomfortable, awkward, or unsafe position. Requirements for designing readable displays are provided below.
a. Accessibility - Displays shall be visually accessible.
b. Parallax Error - Displays shall be located so that they can be read from the design eye point with no discernible parallax.
c. Orientation - Display faces shall be perpendicular to the operator's line-of-sight whenever feasible. The angle between the line-of-sight and the normal to the display shall always be less than 30 degrees.
d. Simultaneous Use - A visual display that must be monitored concurrently with manipulation of a related control shall be located so that it can be read to within required accuracy while adjusting the control.
e. Display Functionality - Displays shall provide positive and unambiguous indication of system state (e.g., a light indicating power on, a blinking cursor indicating ready). These positive indications shall be used consistently throughout the space module.
9.2.3.2.3 Control/Display Grouping Design Requirements
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Requirements for grouping controls and displays are listed below.
a. Functional Grouping - Displays and/or controls that are functionally related shall be located in proximity to one another - arranged in functional groups (e.g., power, status, test).
b. Sequential Grouping - When a unique sequence of control actions exists, the controls and/or displays shall be arranged in relation to one another according to their sequence of use. Within a functional group, the sequence shall be from left to right or top to bottom whenever feasible.
c. Logical Flow Grouping - When there is not a unique sequence or functional grouping of control actions, controls and displays shall be arranged in a manner consistent with their logical flow.
If controls are not to be utilized in any specific sequence, then consider arranging them by importance with the most important or frequently used control in the most accessible position.
d. Functional Group Markings - If several functional groupings of displays and controls are placed in close proximity on a control panel, an effective means of discriminating between them shall be provided (e.g., color coding or outlining).
e. Left-to-Right Arrangement - If controls must be arranged in fewer rows than displays, controls affecting the top row of displays shall be positioned at the far left; controls affecting the second row of displays shall be placed immediately to right of the these, etc.
f. Vertical and Horizontal Arrays - If a horizontal row of displays must be associated with a vertical column of controls or vice versa, the farthest left item in the horizontal array shall correspond to the top item in the vertical array, etc. However, this type of arrangement shall be avoided whenever possible.
g. Multiple Displays - When the manipulation of one control requires the reading of several displays, the control shall be placed as near as possible to the related displays, but not so as to obscure displays when manipulating the control.
h. Separate Panels - When functionally related controls and displays must be located on separate panels and both panels are mounted at approximately the same angle relative to the operator, the control positions on one panel shall correspond to the associated display positions on the other panel. The two panels shall not be mounted facing each other. Controls and displays on separate panels are discouraged.
i. Switch/Control Labeling - Each switch/control shall be labeled to indicate its function to the operator.
9.2.3.2.4 Preferred Control/Display Location Design Requirements
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Design requirements for the placement of displays and controls are provided below.
a. Display Location - The most important and frequently used displays shall be located in a privileged position in the optimum visual zone, providing that the integrity of grouping by function and sequence is not compromised. See
Figure 9.2.4.2.2-2 for a definition of this zone.
b. Control Location - The most important and frequently used controls shall have the most favorable position with respect to ease of reaching and grasping (particularly rotary controls and those requiring fine settings), providing that the integrity of grouping by function and sequence is not compromised.
c. Multi-G Control Placement - Special attention shall be paid to the placement of controls which must be used while the crewmember is subject to either prolonged or transitory acceleration forces above 2-G.
1. In general, these controls shall be located so that the operator's limb is always in contact with the control (i.e., no reaching is required).
2. The requirements for movement from one control to another shall be minimized (e.g., use combined controls with several functions mounted on a single shaft).
3. Rotary controls shall be selected in preference to linear controls whenever possible.
4. When linear controls are necessary, they shall be mounted so that the direction of operation is perpendicular to the direction of G-forces.
5. Hand controls shall be placed so that when the shoulder, elbow, forearm, and wrist are supported, the following minimum movements can be made:
MOVEMENT ACCELERATION
Arm Up to 4-G
Forearm Up to 5-G
(9-G if arm is counterbalanced)
Hand Up to 8-G
Finger Up to 10-G
d. Control/Display Relationships:
1. The relationships of a control to its associated display and the display to the control shall be immediately apparent and unambiguous to the operator.
2. Controls shall be located adjacent to their associated displays and positioned so that neither the control nor the hand normally used for setting the control will obscure the display.
9.2.3.2.5 Consistent Control/Display Placement Design Requirements
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Requirements for maintaining consistency in control and display design are provided below.
a. Similarity - The arrangement of functionally similar or identical displays and controls shall be consistent from panel to panel throughout and between systems, equipment, units, and vehicles.
b. Mirror Images - Mirror image arrangements shall not be used.
9.2.3.2.6 Maintenance Controls/Displays Design Requirements
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Controls and displays used solely for maintenance and adjustments shall be covered or non-
visible during normal equipment operation, but shall be readily accessible when required.
(Refer to Section 12.0, Design for Maintainability, and
Paragraph 9.2.3.2.1b, Gloved Operation, for additional information.)
9.2.3.2.7 Emergency Control/Display Placement Design Requirements
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Requirements for emergency displays and controls are provided below.
(Refer to Paragraph 9.4.4.3, Caution and Warning System Design Requirements, for related information.)
a. Emergency Control/Display Placement - Emergency displays and controls shall be located where they can be seen and reached with minimum delay.
b. Computer-Generated Emergency Displays - Emergency information depicted on existing computer-controlled displays shall be sufficiently conspicuous to attract the user's attention consistently.
9.2.3.2.8 Control/Display Movement Compatibility Design Requirements
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Requirements for control/display movement compatibility are provided below.
a. Consistency of Movement - Controls shall be selected so that the direction of movements of the control will be consistent with the related movement of an associated display, equipment component, or vehicle (except as noted in b below).
b. Complex Movement Control - When the vehicle, equipment, or components are capable of motion in more than two dimensions, exception to 9.2.3.2.8 a shall be made to:
1. Maintain consistency with other systems.
2. Maintain a natural association between control and system movements. For example, forward motion of a directional control causes some vehicles to dive or otherwise descend rather than to simply move forward.
c. Conflict Avoidance - When several controls are combined in one control activity, caution shall be exercised to avoid a situation in which similar movement of different controls results in different systems responses (e.g., control motion to the right is compatible with clockwise roll, right turn, and direct movement to the right).
d. Remote Controls - Where controls are operated at a position remote from the equipment or controlled vehicle, they shall be arranged to facilitate consistency of movement.
e. Movement Direction - When a rotary control and linear display are in the same plane, the part of the control adjacent to the display shall move in the same direction as the moving part of the display.
f. Labeling - When control/display relationships specified herein cannot be adhered to, controls shall be clearly labeled to indicate the direction of control movement required.
g. Time Lag -
1. The time lag between the response of a system to a control input and the display presentation of the response shall be minimized, consistent with safe and efficient system operation. Where such time delay exceeds acceptable limits, the action of the control shall be appropriately modified (by force feedback or other means) to avoid over control.
2. Immediate feedback for operator entries shall have not more than a .2 sec delay.
3. Simple requests for data shall be carried out more rapidly than .5 to 1.0 sec.
4. Changes of entire data pages may be executed in up to 10 sec, depending on the user's expectations and the criticality of the information.
5. If processing requirements result in longer delays, then the system shall acknowledge a control input immediately and provide periodic updates showing the progress of the processing.
(Refer to Paragraph 9.6.2.9.2.d, Response Time, for recommended system response times for interactive computer-generated displays.)
9.2.3.2.9 Control/Display Movement Ratio Design Requirements
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Requirements for designing the relative movement ratios between controls and displays are provided below.
a. Adjustment Time - Control/display ratios for continuous adjustment controls shall minimize the total time required to make the desired control movement (i.e., slewing time plus fine adjusting time) consistent with display size, tolerance requirements, viewing distance, and time delays.
b. Range of Display Movement:
1. When a wide range of display element movement is required, small movement of the control shall yield a large movement of the display element.
2. When a small range of display movement is required, a large movement of the control shall result in a small movement of the display, consistent with accuracy requirements.
c. Coarse/Fine Knob Setting - A rotary knob used for coarse control shall move an associated display element (linear scale) 3-6 times the distance of a fine control knob per revolution of the knob.
d. Bracketing - When bracketing is used to locate a maximum or minimum value (e.g., as in tuning a transmitter), the control knob shall swing through an arc of not less than 10 degrees nor more than 30 degrees either side of the target value in order to make the peak or dip associated with that value clearly noticeable.
e. Counter - When counters are provided, the control/display ratio shall be such that one revolution of the knob produces approximately 50 counts.
9.2.3.2.10 Control/Display Complexity and Precision Design Requirements
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Requirements governing control and display complexity are presented below:
a. Controls/Displays and System Compatibility - The complexity and precision of the control and display system shall be consistent with the precision required by the overall system.
b. Information Processing Ability - Displayed information shall not exceed the user's perception or information processing ability (e.g., displays which are too complex or too briefly presented to be understood.) Display information shall consist of only information that is pertinent to the operator's task at hand. Where it is necessary to have a complex display, means shall be explored to simplify it: by providing an option to choose more or less detail, an option to display data in either an alphanumeric or graphic format , or by organizing the information in spatially isolated, highlighted, or boxed-around groups.
c. Motor Ability - The required operation of controls shall not exceed the user's manipulative ability under the dynamic condition and environment in which human performance is expected to occur (e.g., manual dexterity, coordination, force and torque generation, and reaction time shall not be exceeded).
9.2.4 Human/Workstation Configuration
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9.2.4.1 Human/Workstation Configuration Design Considerations
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9.2.4.1.1 Restraint Selection Design Considerations
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Design considerations for the selection of restraints are provided below.
a. Restraint Types - Types of restraints available for workstations include, but are not limited to, foot restraints, tethers, waist restraints, and handholds.
b. Restraint Design Factors - In choosing a restraint system, factors that should be considered include, but are not limited to, the following: comfort, adjustability, ease of engagement and disengagement, stability provided to the user, and compatibility with required task performance.
c. Adjustability - The goal of restraint adjustment at a workstation should be to optimize both the operator's eye position relative to the displays, and his or her reach envelope relative to controls.
(Refer to Paragraph 11.7.2.2, Personnel Restraints Design Considerations, and
Paragraph 11.8.2.1, Handhold and Handrail Design Considerations, for specific considerations.)
9.2.4.2 Human/Workstation Configuration Design Requirements
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9.2.4.2.1 Workstation Anthropometric Design Requirements
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Workstations shall be designed to accommodate the physical characteristics of the users.
a. Microgravity - The physical dimensions and layout of workstations shall accommodate the user characteristics for microgravity neutral body posture given in
Paragraph 3.3.4.3.
b. User population - The physical dimensions and layout of the workstation shall conform to the characteristics of the specific population of users given in
Paragraph 3.3.1.3.
(Refer to Paragraph 3.3, Anthropometrics and Biomechanics Related Design Data, for further information on anthropometry.)
c. Movement - Workstations shall be laid out in such a way that operator body motion required for workstation functions shall be minimized. Priority shall be given to the most frequently or time critical functions. Micro-g restraint features shall be incorporated into the design.
d. Musculoskeletal Tension - Workstation design shall minimize the musculoskeletal tension required to maintain position/posture required for workstation operation.
9.2.4.2.2 Visual Space Design Requirements
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Good workstation design shall accommodate the visual abilities of users. Requirements and specifications regarding a crewmember's visual space are provided below:
a. Viewing Distance:
1. Minimum - The effective viewing distance to displays, with the exception of visual display terminal (VDT) displays and collimated displays, shall not be less than 330 mm (13 in) and preferably not less than 510 mm (20 in.).
When using a VDT, a minimum viewing distance of 410 mm (16 in.) shall be provided. The recommended distance depends on the detail and resolution of the display, but would generally be greater than 410 mm (16 in.). When periods of scope observation will be short, or when dim signals must be detected, the viewing distance may be reduced to 250 mm (10 in.).
2. Maximum - The maximum viewing distance to displays located close to their associated controls is limited by reach distance and shall not exceed 710 mm (28 in.). For other displays, there is no maximum limit, other than that imposed by space limitations and visual requirements, provided the display is properly designed.
b. Line of Sight - A crewmember's line of sight depends on body position and varies as a function of gravity level as shown in
Figure 9.2.4.2.2-1.
c. Field of View - The field of view for a particular observer position is determined by eye and head movements.
1. The eye movement component for microgravity and 1-G is shown in Figure 9.2.4.2.2-2. (Note that the field of view is measured with respect to eye and head movement ranges shown in
Figure 9.2.4.2.2-1.)
2. The head movement component for 1-G is shown in Figure 9.2.4.2.2-2. Microgravity head movement data are not yet available and probably differs from 1-G.
d. Visual Distractions - Workstations shall be designed so that stimuli distracting to the operator are minimized.
Figure 9.2.4.2.2-1 Line-of-sight
for One-G and Microgravity
Reference: 1, p. 2.2-2; NASA-STD-3000
227
Figure 9.2.4.2.2-2 Eye and Head
Movement Ranges (Line-of-sight Depends on G-Level)
Reference: 2, p. 27 NASA-STD-3000 228
9.2.4.2.3 Workstation Restraints and Mobility Aid Design Requirements
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This section provides requirements for integrating restraints and mobility aids into the workstation environment.
(Refer to Paragraph 11.7.2.3, Personnel Restraints Design Requirements, for specific design requirements relating to different types of restraints.)
a. Neutral Body Posture - The neutral body posture (see Figure
3.3.4.3-1) shall be used in the design of microgravity restraints for long duration use. For short periods of time, significant variation from neutral body posture are acceptable but not desirable.
b. Freedom of Movement - A workstation restraint shall allow the users to reach all required controls and view all required displays without having to assume uncomfortable or awkward postures.
c. Restraint Adjustment
1. Eye Position and Reach - Restraints shall be adjustable so as to achieve the best compromise between eye position (relative to displays) and reach (relative to controls) for crewmembers of differing heights.
2. Adjustment of position shall be rapid and convenient, preferably without crewmembers having to exit restraint.
d. Required Restraint Placement - Foot, waist, or other restraint systems shall be located at all IVA workstations that require a crewmember to perform the following types of tasks.
1. Long-term visual monitoring.
2. Extensive manipulations requiring the use of both hands.
3. Any task that requires the body position to be controlled.
e. Stability - As required, workstation restraints shall provide stability sufficient for:
1. Viewing fine detail.
2. Making fine manual adjustments.
3. Exerting necessary force on controls without causing excessive body displacement.
4. Executing continuous control movement when required.
f. Handholds and Handrails - Workstation handholds and handrails shall meet the following requirements:
(Refer to Paragraph 11.8.2.2, Handhold and Handrail Design Requirements, for additional requirements.)
1. They shall aid in the translation and stability of crewmembers already in foot or other restraints.
2. They shall allow unrestrained crewmembers access to workstation operations to the extent feasible.
3. The physical dimensions and layout of the workstation handholds and handrails shall conform to the characteristics of the specific population of users for whom the system is to be designed.
4. They shall not obstruct visual or physical access to workstations.
5. They shall accommodate multiple personnel as required.
g. Equipment Restraints - Equipment restraints shall be provided to anchor every item of use that is not permanently attached to the workstation.
(Refer to Paragraph 11.7.3, Equipment Restraints.)
9.2.5 Specialized Workstations
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9.2.5.1 Window Workstation
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Since any window in a spacecraft may support mission operations, consideration must be given for its use as a workstation.
9.2.5.1.1 Window Workstation Design Considerations
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The following points should be considered in the design of window workstations.
a. Uses of Window Workstations - Tasks that could involve the use of window workstations are presented below.
1. Coordination of docking and berthing of other modules.
2. Monitoring and support of EVA personnel.
3. Teleoperation of EVA equipment.
4. Support experiments and scientific observations requiring through the window viewing.
5. Support non-workstation functions when not serving as a workstation (e.g., recreational viewing).
(Refer to Paragraph 8.11, Windows Integration, for additional information.)
b. Field of View - A number of factors determine the field of view from a window. These include:
1. Window size.
2. Bezel thickness.
3. Distance of observer from window.
4. Angle from which observer is viewing the window.
(Refer to Figure 8.11.2.2-1, Calculation of Visual Angle From Window, for additional information, and
Paragraph 9.2.5.1.2a, Field of View, for design requirements for window workstation fields of view.)
c. Information Input/Output - Information input/output techniques depend, in part, on the task to be performed. In particular, the need for the operator to maintain continuous visual contact with target stimuli can influence the choice of controls.
1. Information output techniques that help maintain visual contact include:
a) Voice output.
b) Nonverbal auditory signals.
c) Heads-up displays.
d) Helmet mounted displays.
e) Well designed standard displays - These should be positioned to minimize the shift of gaze required to fixate them, and designed to allow the operator to take in information quickly.
2. Information input techniques that help maintain visual contact include:
a) Voice recognition.
b) Position, size, and shape coding of controls.
d. Window Design - The design of workstation windows should be based on a careful analysis of the tasks that will be performed using them and should include the following considerations:
1. Consideration of the perceptual requirements of the tasks that the crewmembers will be required to perform.
2. Consideration of the capabilities and limitations of the equipment that requires through the window sensing.
9.2.5.1.2 Window Workstation Design Requirements
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Design requirements for window workstations are provided below.
(Refer to Paragraph 11.11, Windows, for requirements on the optical properties of windows as they apply to both humans and optical instruments, protection of humans from harmful window-related radiation, and the protection and maintenance of windows.)
a. Field of View:
1. Design Eye Volume - The required field of view for a window workstation shall be attainable with the observer's eye position located anywhere within a specified design eye volume. The design eye volume shall satisfy the following requirements.
a) The design eye volume shall conform to the characteristics of the specific population of users for whom the system is to be designed when using the restraint system.
b) The design eye volume shall accommodate all movements necessary to operate controls and view displays.
c) The design eye volume shall accommodate normal crewmember movement and changes of posture required for comfort (e.g., a crewmember shall not be required to maintain eye position fixed within a small volume of space for an extended period of time).
b. Window Shape - Rectangular rather than round viewing areas shall be used on windows whenever feasible. The purpose is to provide orientation cues for crewmember body position and/or extravehicular objects relative to the space module.
c. Multi-Observer Windows - When feasible, windows shall accommodate more than one observer. Window shape and work area layout shall be designed to this end.
d. Shielding:
1. Luminance control - The capability to reduce window transmissivity through the addition of neutral filtering shall be provided. This shall allow crewmembers to work comfortably with extravehicular luminance conditions.
2. Complete closure - The capability to completely block light transmittal through a window shall be provided.
3. Sun Shades - When necessary, sun shades shall be provided. These shades shall be adjustable unless otherwise specified.
e. Color Discrimination - Windows used for making color discriminations shall possess neutral spectral transmission so that perceived target object hues are not altered.
f. Cleaning - Inside window surface shall be easily cleaned without damaging window.
(Refer to Paragraph 11.11.3.5, Window Maintenance Design Requirements, for additional information on window maintenance.)
g. Reflections - Workstation and work area design and lighting shall minimize reflections from the window to the lowest feasible level.
(Refer to Paragraph 11.11.3.1.7, Visual Protection Design Requirements, for information on antireflection techniques.)
h. Dark Adaptation - When dark adaptation is required at a window workstation, the workstation area shall allow dimming of lights to the required level without unduly interfering with other space module activities.
i. Display Shielding - Displays shall be shielded from sunlight entering the window or be designed to be legible in sunlight.
j. Control Placement - Control placement and design shall allow crewmembers to assume a position relative to the window that optimizes viewing conditions through the window.
k. Restraints - The design and placement of window workstation restraints shall allow up to four continuous hours of comfortable use.
9.2.5.2 Maintenance Work Area
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9.2.5.2.1 Maintenance Work Area Design Considerations
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Considerations pertaining to information presentation/retrieval at workstations is presented below.
a. Computer Access - The maintenance workstation should provide computer access to all maintenance-related programs.
b. Communication - The maintenance workstation should permit real-time voice and data communications with other crewmembers and/or the ground-based maintenance system as needed to provide assistance in maintenance and repair.
c. Hardcopy - A method for managing and restraining hardcopy material (books, checklists) should be designed into all workstations. Hardcopy positioning should consider lighting requirement, facing angles, print size, eye distance, and neutral body posture.
d. Data Presentation - The maintenance workstation should be capable of displaying maintenance-related data such as schedules, procedures, diagnostic details, and forecast maintenance plans.
e. Bar Code Reader - A Bar Code Reader should be provided which will allow automatic reading of the labeling system to enable cross matching of information within the space module computer system.
f. No-Hands Input/Output - Insofar as possible, a no-hands-required input/output device should be made available at the maintenance workstation.
9.2.5.2.2 Maintenance Work Area Design Requirements
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a. Layout/Construction Requirements - The Maintenance Work Station (MWS) shall serve as the primary location for servicing and repair of maximum sized replacement unit/system components. The MWS provides a controlled environment with user interfaces to the electrical, data, power and video systems.
1. Location - The maintenance work area shall be located in an easily accessible area.
2. Equipment size capability - The maintenance work area shall be sized to accommodate the maximum-sized replacement unit/system that may require repair or maintenance.
3. Transparent Surfaces - All transparent surfaces (e.g., displays, windows, etc.) shall be scratch/mar resistant, antifog and anti-icing where possible, and shatter resistant.
4. Capabilities - The maintenance work area shall provide the capability to operate the electrical, mechanical, vacuum and fluid support during corrective and preventive maintenance.
5. The maintenance work area shall have general purpose diagnostic equipment and shall accommodate special purpose diagnostic equipment.
6. The maintenance work area shall be equipped with a set of hand tools and with general purpose test and ancillary equipment and shall have ample stowage space for such tools, equipment, and materials (e.g., wire, screws, tape, nuts and raw stock).
7. The maintenance work area shall be developed with consideration being given toward providing capabilities for performing minor contingency fabrication tasks, including but not limited to turning, bending, forming, drilling, and bonding.
b. Contamination:
(Refer to Paragraph 13.2.3, Housekeeping Design Requirements, for additional information on contamination control.)
1. Cleaning:
a) Exposed surfaces shall be designed to provide for easy cleaning. Crevices and narrow openings which can collect liquid or particulate matter and which cannot be readily cleaned without special tools shall be avoided.
b) Any type of grid or uneven surface shall be configured to permit cleaning of all areas.
c) The maintenance work area shall have a vacuum or evacuation system for purging and cleaning replacement units/systems. The vacuum effluence shall be contained to preclude external environment contamination.
d) The maintenance work area shall provide a means to control odors and/or to remove particulates from a system. All filters shall be easily accessible for cleaning and/or replacement. Means shall be provided to prevent leakage of any entrapped material from a filter unit during removal.
e) Maintenance work area shall have the capability for the collection and disposal of debris, odors, particulate matter, and liquid from the work area atmosphere as well as from exposed interior surfaces of the workstation.
f) Contamination Control:
1) A means shall be provided for passive contamination control in the transport of devices to and from the maintenance workstation.
2) The maintenance work area shall be provided with means to measure and monitor the contamination level within the work area, including the capability to measure surface contamination level.
3) A means shall be provided for contamination control which assure prevention of mutual contamination between the ambient environment and the work area.
g) A means shall be provided for a passive contamination control method for IVA maintenance operations actions which will be performed remote from the maintenance work area.
2. Hazardous operations - The capability to seal hazardous operations from other areas shall be provided at the Maintenance Workstation for the duration of the operation.
3. Particulate Matter Retention - The maintenance workstation shall be capable of particulate matter/ odor retention and effluent scrubbing/capture.
c. Replacement Unit Interface - The maintenance work area shall be able to interface with the failure detection, fault isolation and built-in test capability of replacement units as required.
d. Maintenance Aids Package - The maintenance work area shall be provided with a common maintenance aids package which will include but not be limited to: audio, video, and data communication links; a data management system interface and utilities.
e. Power - The maintenance work area shall have the capability to provide conditioned and converted power to support replacement unit design specified requirements for servicing and repair activities.
f. Illumination - Work area illumination shall be as specified in Figure
8.13.3.1.2-1.
9.2.6 Portable Workstation/Terminals
{A}
Requirements for portable workstations are given below:
a. Shall provide for restraint per requirements given in Paragraph
11.7.3.3.
b. Shall provide for wireless operation.
c. If cable connections are required, dedicated connectors shall be used to interface the module with the facility by using a maximum cable length of 3 meters.
d. Shall provide handles or grasp areas per requirements given in Paragraph
11.6.3.
9.3 CONTROLS
{A}
9.3.1 Introduction
{A}
This section provides considerations and requirements for the design and use of controls. The data are for ungloved operation unless otherwise stated. Where operating forces are given, they are for microgravity conditions. This should not pose a problem if crewmembers are adequately restrained.
(Refer to Paragraph 14.4, EVA Workstations and Restraints, for gloved operations. Refer to
Paragraph 4.9, Strength, for additional information on the application of force.)
9.3.2 Controls Design Considerations
{A}
9.3.2.1 Input Devices Design Considerations
{A}
The advantages and disadvantages of different controls are presented in Figure
9.3.2.1-1. Recommended control uses are also included in this figure. Similar data for computer input devices are presented in
Paragraph 9.3.2.2.
(Refer to Paragraph 9.3.4, Examples - Control Design Solutions, for an assessment of controls used aboard Skylab.)
Figure 9.3.2.1-1 Advantages and
Disadvantages of Different Control Types
| Advantages |
Disadvantages |
| a. Knob, discrete position rotary |
|
Used when 4 or more detended positions are required.
Resistant to accidental actuation
|
Not recommended for 2 position functions.
relatively slow
|
| b. Knob, continuous position rotary |
|
Good for precise settings
Single-or multi-turn capability
|
Potential parallax error
Relatively slow
Susceptible to misinterpretation if multiple turn
Sensitive to accidental activation
Difficult (time consuming) to re-establish setting if switch is moved inadvertently
|
| c. Knobs, ganged |
| Efficient use of space |
Three-knob assembly not recommended
Relatively slow
Not recommended for gloved use
Susceptible to erroneous settings
Not recommended when frequent changes are required.
One know may move other knob if inter-knob friction
exists (may require two handed operation).
|
| d. Thumbwheels |
| Compact |
Not recommended for fine control
Slow, not recommended for high traffic functions
Can cause intermediate and inadvertent inputs
Susceptible to inadvertent activation
Position or selection may be difficult to assess in dim light
|
|
e. Cranks
|
|
Used when multiple rotations are required
Fast
Can handle high forces
Can be used for coarse and fine adjustments
|
Requires space
Susceptible to accidental movement
Tempting hand hold or grasp under microgravity conditions
|
|
f. Handwheels
|
|
Good for high forces
Suitable for 2 handed use
|
Requires substantial space
Not good for fine adjustments
May require two-handed operation
High force operation will require good restraint system
Temptation to use as hand hold or grasp under microgravity conditions
|
|
g. Levers
|
|
Good for high forces
Status is obvious
|
Large space requirements
Susceptible to accidental displacement
Temptation to use as hand hold or grasp under microgravity conditions
|
|
h. Toggle switches
|
|
Used for 2 or 3 discrete positions
Efficient use of space
Setting is obvious to user
|
Four or more positions should be avoided
Susceptible to inadvertent activation
Often requires guards or shield, especially in microgravity
|
|
i. Push button
|
|
Efficient use of space
Fast activation
|
State of activation is not always obvious
Susceptible to accidental activation
Lighted push button cause continuous power drain
May require secondary status indication
Bulb failure can lead to erroneous interpretation of status
|
| j. Foot operated switches |
| Can be used when hands are occupied |
Cannot use with foot restraints
Susceptible to accidental activation
Not recommended for critical operations, frequent use or fine adjustments
Can induce forces to move operator out of position if used in microgravity without restraints
|
| k. Pedals |
|
Use when both hands occupied
High force capability
May be used where pedal has created a stereotyped expectancy
|
Cannot use with foot restraints
Can include forces to move operator out of position if not restrained
|
|
l. Rocker switches
|
|
Efficient use of space
Will not snag clothing
Status is obvious
|
Susceptible to accidental activation
Can be difficult to read three-position rocker switches
|
| m. Push-pull controls |
|
Used for 2 position control
Efficient use of panel space
May be used in a multi-mode fashion (e.g., on-off and volume control) to save space
|
Difficult to determine positions when used for multiple position control
Susceptible to inadvertent activation
|
| n. Slide switches |
|
Can be discrete or continuous
Good for large number of discrete positions
Provide easy recognition of relative switch setting
|
Continuous slide switches susceptible to mispositioning
Can be difficult to position continuous slide switch precisely
|
| o. Legend switches |
|
Good in low illumination (if self illuminated)
Fast activation
Effective way to label switches
Efficient use of panel space
|
Not recommended for more than two positions
State of activation is not always obvious
|
| p. Printed circuit (DIP) switches |
| Very space efficient |
Slow
Usually require stylus to set
Small size makes switch difficult to read
May require stabilized hand to set and to avoid excess force
|
| q. Key operated switches |
|
Prevent unauthorized operation
Permits flush panel for seldom operated switches
|
Slow to operate
Must keep track of separate key
Key slot susceptible to contamination if not shielded - especially in microgravity
|
Reference: 2, pp. 71-110, NASA-STD-3000 231c
9.3.2.2 Computer Input Devices Design Considerations
{A}
Design considerations for a number of different devices used to interact with computers are provided below.
a. Joystick - Joysticks are used primarily to control cursor position on a VDT. Advantages and disadvantages of using joysticks are provided in
Figure 9.3.2.2-1a.
1. Isotonic (displacement) joystick - Isotonic means that cursor movement depends on direction and displacement but not the speed or force with which the joystick is moved. Isotonic joysticks are well suited for tasks in which positioning accuracy is more critical than positioning speed.
2. Isometric joystick - The isometric joystick lever deflects only minimally in response to applied force, but may deflect perceptibly against a stop at full applied force. Cursor movement is controlled by the direction and force applied to the lever. Isometric joysticks are particularly appropriate for applications that:
a) require the cursor to return to center after each entry or readout.
b) involve feedback to the operators that is primarily visual (from some system response) rather than kinesthetic from the joystick itself.
c) involve minimal delay and tight coupling between control and input system reaction.
b. Four Arrow Key Control - The use of four keyboard keys (left, right, up, and down arrows) to control cursor position should allow movement in discrete steps, and continuous movement with continued depression of a particular key.
Advantages and disadvantages of four arrow key control are shown in Figure
9.3.2.2-1b.
c. Light Pen - The light pen is a light-sensing device used primarily to indicate position on a CRT screen. It may also be adapted for reading bar coding.
Advantages and disadvantages of using this device are provided in Figure
9.3.2.2-1c.
d. Mouse - The mouse is a small handheld device that can be moved across any flat surface to control the position of a follower on an associated display. The mouse can contain a small number of function keys.
Advantages and disadvantages of using a mouse are provided in Figure
9.3.2.2-1d.
e. Track Ball - A track ball device consists of a sphere suspended on low-friction bearings. It is turned in place (usually by hand) to control the position of a follower on an associated display.
Advantages and disadvantages of using track balls are provided in Figure
9.3.2.2-1e.
f. Stylus and Grid - This device consists of a grid with a spatial layout that corresponds to that of the display. The grid senses the position of the stylus (usually handheld) to control the position of a follower on the display.
Advantages and disadvantages are provided in Figure
9.3.2.2-1f.
g. Touch-Sensitive Device - A device with a spatial layout that corresponds to that of the screen. It is activated by being touched and records the location of the touch. It generally consists of a transparent surface attached directly to the face of a VDT and can be used for cursor control or to activate menu items, icons, etc.
Advantages and disadvantages are provided in Figure
9.3.2.2-1g.
h. Voice Activation - A voice-activated system recognizes words or sequences of words spoken by an operator and responds as if a command was entered manually. The words or word sequences must be specified in advance. One characteristic of voice recognizers is the speaker dependence versus independence. Speaker dependent systems require the users to train the system to their voice before using the system while the speaker independent systems do not require such training.
Another characteristic of voice recognizers is the speech input rate. Some recognizers can only accept single, isolated utterances. Others can accept phrases or even continuous, conversational-type speech. This is a new technology undergoing rapid changes.
Advantages and disadvantages are provided in Figure
9.3.2.2-1h.
Figure 9.3.2.2-1 Advantages and
Disadvantages of Computer Input Devices
| Advantages |
Disadvantages |
|
a. Joystick
|
|
Can be used comfortably with minimum arm fatigue
Does not cover parts of screen in use
Expansion or contraction of cursor movement is possible
|
Slower than a light pen for simple input
Must be attached, but not to the display
Unless there is a large joystick, an inadequate control/display ratio will result for positional control
The displacement of the joystick controls both the direction and the speed of cursor movement
Difficult to use for free-hand graphic input
Not good for operation selection
|
|
b. Four arrow cursor control
|
|
Allows accurate positioning of the cursor
May provide positive transfer and advantages associated with touch typing
Allows for nondestructive movement of the cursor
Requires little of no training
|
Should not be used for free-hand graphics |
| c. Light pen |
|
Fast for simple input
Good for tracking moving objects
Minimal perceptual motor skill needed
Good for gross drawing
Efficient for successful multiple selection
User does not have to scan to find a cursor somewhere on the screen
May be adaptable to bar coding
|
May not feel natural to user, like a real pen or pencil
May lack precision because of the aperture, distance from the CRT screen surface, and parallax
Contact with the computer may be lost unintentionally
Frequently required simultaneous button depression may cause slippage and inaccuracy
Must be attached to terminal, which may be inconvenient
Glare problem if pen tilted to reduce arm fatigue
Fatiguing if pen is held perpendicular to work surface
If pointed to dark area, may require user to flash the screen to fine pen
One-to-one input only (zero order control)
May be cumbersome to use with alternate, incompatible entry methods, like the keyboard
Tends to be used for purposes other than originally intended, e.g., for key depression
Tends to be fragile
Hand may obstruct a portion of screen when in use
Care must be taken to provide adequate "activate" area around choice point
Cannot be used on gas panel
|
|
d. Mouse
|
|
Relatively fast
Has low error rates for large targets
Allows user to concentrate attention on VDT screen
|
Requires additional flat work surface
Difficult to use for free-hand graphic input
High error rates with small targets
Lost time when mouse held backwards or sideways
Some training needed
Wheels slipping sometimes a problem
Must be adapted for microgravity use
|
|
e. Track ball
|
|
Ball excellent for three-dimensional rotation of objects
Efficient use of space
Allows use to concentrate attention on VDT screen
Unaffected by microgravity if properly designed
|
Inconvenient or impossible to have integrated "activate" switch on the ball
May need two devices to accommodate handedness
|
|
f. Stylus and grid
|
|
Excellent for graphic entry
Can be designed so that the user works on a horizontal surface
Multipurpose input device
Minimal difficulty going from graphic input if character is built into the system, and the tablet is used for this input.
Spatial correspondence between displays and control movement
|
Extra space required on work surface
Displacement of visual feedback from motor activity may cause coordination problems
Entering handprinted characters to be recognized by the system is very slow (fewer than 40 characters/min) compared with typewriter entry (averaging 200 recognition characters/min.)
|
| g. Touch sensitive devices
|
|
|
No separate input device needed
Fast
|
Low resolution
Finger can block view
Fingerprints on screen
Tires are in one-G
Susceptible to inadvertent actuation in microgravity
|
| h. Voice Activation |
|
|
Does not require hands
Does not require user to shift gaze
Useful for no lights or low light condition conditions
Allows simultaneous activation of more than one control mode
Could be used in lieu of a translator, allowing natural, conversational version of different languages to control complicated systems
A speaker dependent system prevents an unauthorized person from issuing commands verbally
|
Entry can be slow
Must use specified vocabulary
May require headset
Speaker dependent systems must be individualized to specific user
If individual's voice change (e.g. becomes stressed) a speaker dependent system may not respond
Speaker dependent systems require template loading time
Background noise may interfere with recognition
Speaker independent system may allow unauthorized people to issue commands.
|
Reference: 279, pp. 8-6 to 8-9, NASA-STD-3000 232b
9.3.3 Control Design Requirements
{A}
9.3.3.1 General Requirements
{A}
General requirements for the design of controls are provided below.
a. Standardization - Controls shall be standardized to the maximum extent practical. Specific aspects to be standardized include, but are not limited to, the following areas:
1. Control operation.
2. Control mounting and guarding.
3. Control orientation.
4. Control size and color.
5. Nonstandardization of control design shall be employed only if meaningful.
b. Multi-g Controls - Controls to be used under prolonged or transitory acceleration forces above 2 g's shall be designed to accommodate the crewmember's altered physical abilities.
(Refer to Paragraph 9.2.3.2.4c, Multi-g Control Placement, for additional information.)
c. Microgravity Controls - Crew restraints shall be provided for use at all microgravity workstations.
d. Detent Controls - Detent controls shall be selected over continuous controls whenever the operational mode requires control operation in discrete steps.
e. Stops - Stops shall be provided at the beginning and end of the range of control positions if the control is not required to be operated beyond the indicated end positions or specified limits.
f. Load Limit - Control shall withstand the crew-imposed limit loads given in
Figure 9.3.3.1-1 as a minimum.
g. Blind Operation - Where blind operation (i.e., actuation without visual observation) is necessary, the controls shall be shape coded or separated from adjacent controls by at least 13 cm (5 in.).
(Refer to Paragraph 9.2.3.1, Control/Display Placement and Integration - Design Requirements, for additional information.)
h. High-Force Controls - In general, controls requiring operator forces exceeding the strength limits of the lowest segment of the expected user population shall not be used. High force controls shall only be used when the operator's nominal working position and/or restraint system provides proper support.
i. Miniature Controls:
1. Miniature controls shall be used only when severe space-to-required-functionality limitation exists and use by a suited crewmember is not required.
2. Miniature controls shall be avoided when frequent access to controls is required.
3. The movements of miniature controls shall be similar to those of standard controls.
(Refer to Paragraph 9.2.3.2.8, Control/Display Movement Compatibility - Design Requirements, and
Paragraph 9.2.3.2.9, Control/Display Movement Ratio - Design Requirements, for information on standard controls.)
4. The actuation of miniature controls shall be made as easy as possible without subjecting them to accidental actuation.
i. Emergency or Critical Controls - Emergency or Critical Controls shall be coded or labeled.
Figure 9.3.3.1-1 Maximum Crew-Induced
Design Limit Loads (Controls)
| Item |
Type of load |
Design limit load |
Direction of load |
| Levers, handles, operating wheels |
Push or pull concentrated on most extreme tip or edge |
220N(50 lbf) |
Any direction |
| Small knobs |
Torsion |
15 Nm(11 ft-lb) |
Either direction |
Reference: 1, p. 4.9-2 NASA-STD-3000 233
9.3.3.2 Accidental Actuation Design Requirements
{A}
Requirements for reducing accidental actuation of controls is presented below.
a. Design and Location - Controls shall be designed and located so as to minimize susceptibility to being moved accidentally. Particular attention shall be given to critical controls whose inadvertent operation might cause damage to equipment, injury to personnel, or degradation of system functions.
b. Protective Methods - Adequate protection shall be provided for controls that are susceptible to accidental actuation. Protective methods include, but are not limited to, those listed below.
1. Locate and orient the controls so that the operator is not likely to strike or move them accidentally in the normal sequence of control movements.
2. Recess, shield, or otherwise surround the controls by physical barriers. The control shall be entirely contained within the envelope described by the recess or barrier.
3. Cover or guard the controls. Safety or lock wire shall not be used.
4. If a cover guard is used, its location when open shall not interfere with the operation of the protected device or adjacent controls.
5. Provide the controls with interlocks so that extra movement (e.g., lifting switch out of a locked detent position) or the prior operation of a related or locking control is required.
6. Provide the controls with resistance (i.e., viscous or coulomb friction, spring-loading, or inertia) so that definite or sustained effort is required for actuation.
7. Provide the controls with a lock to prevent the control from passing through a position without delay when strict sequential actuation is necessary (i.e., the control moved only to the next position, then delayed).
c. Noninterference - Protection devices shall not interfere with the normal operation of controls or the reading of associated displays.
d. High-Traffic Areas - Critical controls shall not be located in high-traffic paths or translation paths. If controls must be placed in these locations, means shall be used to prevent inadvertent actuation (i.e., pull to unlatch toggle switches).
(Refer to Paragraphs 9.3.3.2.b, Protective Methods, and
8.7.3, Traffic Flow Design Requirements, for additional information.)
e. Dead-Man Controls - Where appropriate, controls, which result in system shutdown to a noncritical operating state when force is removed, shall be utilized where operator incapacity can produce a critical system condition.
f. Barrier Guards:
1. Barrier guard spacing requirements for use with toggle switches, rotary switches, and thumbwheels is shown in
Figure 9.2.3.2.1-1 and 9.3.3.2-1.
(For gloved operation, refer to Paragraph
14.4.3.2, EVA Control and Display Design Requirements.)
2. Accidental actuation of controls can result when crewmembers use barrier guards as handholds. Barrier guards shall be designed and located so as to minimize this problem.
g. Recessed Switch Protection - Under conditions where barrier guards are not applicable, rotary switches that control critical experiment or vehicle functions shall be recessed as shown in
Figure 9.3.3.2-1.
h. Detachment - Covers and guards shall be designed to prevent accidental detachment during operational periods.
i. Position Indication - When protective covers are used, control position shall be evident without requiring cover removal.
j. Hidden Controls - When hidden controls (i.e., controls that cannot be directly viewed) are required they shall be guarded to prevent inadvertent actuation.
k. Hand Controllers - Hand controllers shall have a separate on/off control to prevent inadvertent actuation when the controller is not in use.
l. Circuit Breaker Protection - When circuit breakers are ganged in a common array, a cover shall be used as an additional security measure to prevent inadvertent actuation or damage.
Reference: 1, p. 4.9-10, NASA-STD-3000 234
9.3.3.3 Control Types Design Requirements
{A}
9.3.3.3.1 Knob Design Requirements
{A}
Requirements for the design of knobs are provided below.
a. Discrete Rotary Selection Switches:
1. General:
a) Rotary selector switches shall be used when four or more detented positions are required for discrete functions.
b) Rotary selector switches shall not be used for a two-position function unless ready visual identification of control position is of primary importance, and speed of control operation is not critical, or unless the use of other types of switches is not feasible.
2. Displacement - Up to 12 switch positions may be provided. Standard distance between positions shall be 30 degrees.
3. Knob dimensions - Pointer knobs of the type illustrated in Figure
9.3.3.2-1 are preferred for general use. Dimensions and alternate designs are, in order of preference, described within MIL-K-25049 and MIL-H-8810 (most preferred), MIL-STD-1472, AFSC DH 2-2 and MIL-STD-1348.
4. Separation and arrangement:
a) Rotary selector switches shall be designed with a moving pointer and a fixed scale.
b) The pointer knob shall be mounted sufficiently close to its scale to minimize parallax error between the pointer and the scale markings. When viewed from the normal operator's position, the parallax error shall not exceed 25% of the distance between scale markings.
c) Switch design and scale placement shall be such that there is no reasonable possibility of confusing the pointer-end and nonpointer-end of a knob.
5. Resistance - Switch resistance shall be elastic, building up, then decreasing as each position is approached, so that the control snaps into position without stopping between adjacent positions. The torque required to turn the switch from one detent position to another shall be no less than 9 N-cm (12 in). oz) at breakout and no more than 70 N-cm (100 in. oz) just prior to dropping into the next detent position.
6. Direction of movement - The order of positions shall be such that clockwise movement indicates on ascending order, increased performance, etc.
(Refer to Paragraph 9.2.3.2.9, Control/Design Movement Compatibility - Design Requirements, for additional information of control movement.)
b. Continuous Rotary Control Knobs:
1. General:
a) Continuous rotary control knobs (e.g., rheostats, potentiometers) shall be used for precise adjustment of system parameters.
b) Continuous controls may be either single-turn or multi-turn.
2. Displacement - Single-turn controls shall have a preferred standard deflection of 240 degrees, between limits located at the 8 o'clock and 4 o'clock positions.
3. Resistance - The torque required to reposition the knob shaft shall be 6 to 25 N-cm (8 to 36 in. oz).
c. Ganged Control Knobs:
1. Use - Use of ganged control knobs shall be limited to two-knob assemblies.
2. Limitations - Ganged knob configuration shall not be used under the following conditions.
a) Extremely accurate or rapid operations are required.
b) Frequent changes are necessary.
c) Heavy gloves may be worn by the operator.
3. Dimensions, torque and separation - Dimensions, torque and separation of ganged control knobs shall conform to
Figure 9.3.3.3.1-1.
4. Serration of ganged control knobs:
a) Knobs shall be serrated.
b) Fine serrations shall be used on precise adjustment knobs.
c) Coarse serrations shall be used on gross adjustment knobs.
5. Marking of ganged control knobs:
a) An indexing mark or pointer shall be provided on each knob.
b) Marks or pointers shall differ sufficiently to make it apparent which knob indexing mark is being observed.
6. Knob/display relationship - When each knob of a ganged assembly must be related to an array of visual displays, the knob closest to the panel shall relate to the left most display in a horizontal array, or the uppermost display in a vertical array (see
Figure 9.3.3.3.1-1).
7. Inadvertent operation - When it is critical to prevent inadvertent actuation of one knob as the other is being adjusted, a secondary knob control movement shall be required (e.g., pressing the top knob before it can be engaged with its control shaft).
Figure 9.3.3.3.1-1 Ganged Control
Knobs
 |
|
Dimensions |
| Two knob assembly |
Three knob assembly |
| H1 |
H2 |
D1 |
D2 |
H1 |
H2 |
H3 |
D1 |
D2 |
D3 |
| Minimum |
16 mm (5/8 in) |
13 mm (1/2 in) |
13 mm (1/2 in) |
22 mm (7/8 in) |
19 mm (3/4 in) |
19 mm (3/4 in) |
6 mm (1./4 in) |
13 mm (1/2 in) |
44 mm (1-3/4 in) |
75 mm (3 in) |
| Maximum |
|
|
|
100 mm (4 in) |
|
|
|
|
|
100 mm (4 in) |
| |
Torque |
Separation |
| |
To and including 25 mm (1 in) diameter knobs) |
Greater than 25 mm (1 in) diameter knobs |
One hand individually
Bare |
Two hands simultaneously
Bare |
| Minimum |
|
|
25 mm (1 in) |
50 mm (2 in) |
| Optimum |
|
|
50 mm (2 in) |
75 mm (3 in) |
| Maximum |
32 mN-m (4.5 in-oz) |
42 mN-m (6 in-oz) |
|
|
Reference: 2, p. 80, NASA-STD-3000 235
9.3.3.3.2 Thumbwheel Control Design Requirements
{A}
Design requirements for thumbwheel controls are provided below.
a. Discrete Position Thumbwheels :
1. Discrete position thumbwheels shall have 10 or fewer detent positions.
2. The standard distance between positions shall be 36 o.
3. Maximum deflection shall be 360 or less if 10 or fewer positions are required.
4. Each position around the circumference of a discrete thumbwheel shall have a slightly concave surface or shall be separated by a high-friction (e.g., knurled) area that is raised from the periphery of the thumbwheel.
5. Resistance shall be elastic, building up and then decreasing as each detent is approached so that the control snaps into position without stopping between adjacent detents. The resistance of discrete thumbwheel controls to movement shall be between 11 and 34 N-cm (16 to 48 in. oz).
6. Movement of the thumbwheel forward, up, or to the right shall produce an increase in the setting value.
b. Continuous Types Thumbwheels:
1. Continuous type thumbwheels shall have a standard deflection of 300o.
2. Hard stops shall be provided to limit the maximum travel of continuous thumbwheels.
3. Continuous thumbwheels shall employ high-friction raised areas to facilitate movement.
4.The resistance of continuous thumbwheel controls to movement shall be between 1 and 4 N-cm (2 and 6 in. oz.).
5. Movement of the thumbwheel forward, up, or to the right shall produce an increase in the setting value.
c. Coding:
1. Thumbwheel controls shall be coded by location, labeling, or color (e.g., reversing the colors of the least significant digit wheel as on typical odometers).
2.Where used as input devices, thumbwheel switch OFF or NORMAL positions shall be color coded to permit a visual check that the digits have been reset to these positions (if applicable).
9.3.3.3.3 Valve Control Design Requirements
{A}
Requirements for the design of valve controls are provided below.
a. Low-Torque Valves - Valves requiring 1 Nm (10 in-lb) or less for operation are classified as valves and shall be provided with a handle, 5.5 cm (2.25 in.) or less in diameter,
(see d below).
b. Intermediate-Torque Valves - Valves requiring between 1 and 2 N-m (10 and 20 in-lb) for operation are classified as intermediate torque valves and shall be provided with a central pivot type handle 5.5 cm (2.25 in.) or greater in diameter, or a level (end pivot) type) handle, 7.5 cm (3 in.) or greater in length (the exact size shall be determined by the particular application).
c. High-Torque Valves - Valves requiring 2 Nm (20 in-lb) or more for operation are classified as valves and shall be provided with handles greater than 7.5 cm (3 in.) in length.
d. Handle Dimensions:
1. Valve handles shall approximate the configuration illustrated in Figures 9.3.3.3.3-1 and
9.3.3.3.3-2.
2. Handles shall be contoured and finished so as to permit ease of operation.
3. Circular handles, when used, shall have crowns or shall employ concave areas or convex projections along the periphery of the handle.
e. Valve Controls - Rotary valve controls shall open the valve with a counterclockwise motion.
Reference: 194, p. 16, NASA-STD-3000 236
Reference: 194, p. 16, NASA-STD-3000 237
9.3.3.3.4 Crank Design Requirements
{A}
Requirements for the design of cranks are provided below.
a. Dynamics:
1. Where cranks are used for tuning or other processes involving numerical selection, each rotation shall correspond to a multiple of 1, 10, 100, etc.
2. The gear ratio and dynamic characteristics of such cranks shall allow precise placement of the follower (e.g., crosshairs) without overshooting or undershooting and successive corrective movements.
b. Grip Handle - The crank grip handle shall be designed so that it turns freely around its shaft.
c. Dimensions, Resistance, and Separation - Dimensions, resistance, and separation between adjacent swept circular areas of cranks shall conform to the criteria of
Figure 9.3.3.3.4-1.
d. Folding Handle - If a crank handle could become a hazard to persons passing by, or it is critical that the handle not be inadvertently displaced by being accidentally bumped, a folding handle type control shall be used. Such a control shall be designed so that the handle is firmly held in the extended position when in use and folded when not in use.
 |
| Load |
Specification |
Handle |
R, Turning radius |
| L, Length |
D, Diameter |
Rate below 100 RPM |
Rate above 100 RPM |
| mm |
in |
mm |
in |
mm |
in |
mm |
in |
| Light loads - less than 22 N (5 lb) (wrist and finger movement) |
Minimum |
25 |
1 |
10 |
3/8 |
38 |
1-1/2 |
13 |
1/2 |
| Preferred |
38 |
1-1/2 |
13 |
1/2 |
75 |
3 |
65 |
2-1/2 |
| Maximum |
75 |
3 |
16 |
5/8 |
125 |
5 |
115 |
4-1/2 |
| Heavy loads - More than 22 N (5 lb) (arm movement |
Minimum |
75 |
3 |
25 |
1 |
190 |
7-1/2 |
125 |
5 |
| Preferred |
95 |
3-3/4 |
25 |
1 |
-- |
-- |
-- |
-- |
| Maximum |
-- |
-- |
38 |
1-1/2 |
510 |
20 |
230 |
9 |
Reference: 2, p. 83; NASA-STD-3000 238
9.3.3.3.5 Handwheel Design Requirements
{A}
Requirements for the design of handwheels are provided below.
a. Restraints - When designed for use in microgravity, adequate restraints shall be provided for the operator.
b. Turning Aids - Knurling, indentation, high-friction covering, or a combination of these shall be built into the handwheel to facilitate operator grasp for applying maximum torque and to reduce the possibility of the wheel being jerked from the operator's hands.
c. Spinner Handles - For applications where the wheel may be rotated rapidly through several revolutions, a spinner handle may be added. Such handles shall not be used, however, if the projecting handle is vulnerable to inadvertent displacement of a critical wheel setting or if it creates a safety hazard.
9.3.3.3.6 Lever Design Requirements
{A}
Requirements for the design of levers are provided below.
a. Coding - When several levers are grouped in proximity to each other, the lever handles shall be coded.
Refer to Paragraph 9.5.3.2, Coding Design Requirements, for additional information.)
b. Length - The length of levers shall be determined by the mechanical advantage needed.
9.3.3.3.7 Toggle Switch Design Requirements
{A}
Requirements for the design of toggle switches are provided below.
a. Dimensions - Dimensions for a standard toggle switch shall conform to the values presented in
Figure 9.3.3.3.7-1.
b. Indication of Actuation:
1. An indication of control actuation shall be provided (e.g., snap feel, audible click, associated or integral light).
2. Switch design shall preclude stoppage between positions.
3. Visual verification of switch position shall be obtainable at a glance from any viewing angle.
c. Operating Force:
1. Operating force shall be in the range of 3 to 30 N (0.63 to 6.25 lbf).
2. The selected force value shall be dependent upon the specific application (e.g., high-force switches are especially suited for applications where positive-feel is important).
3. For lever-lock (pull-to-unlock) toggle switches, resistance of lift-to-unlock mechanisms shall not exceed 13 N (3 lbf).
d. Orientation - The preferred direction of toggle switch operation shall be vertical. Horizontal actuation of toggle switches shall be employed only for compatibility with the controlled function or equipment location.
e. Position Designation - Switch actuation shall control the system or subsystem functions as indicated in
Figure 9.3.3.3.7-2.
f. Off Position - Where a third position is added for off, the off mode shall be located in the center position, except where this would compromise equipment performance. In this case, off shall be in the bottom position.
 |
| |
Dimensions |
Resistance |
L
Arm length |
D
Control tip |
Small Switch |
Large Switch |
| Minimum |
13 mm (1/2 in) |
3 mm (1/8 in) |
2.8 N (10 oz) |
2.8 N (10 oz) |
| Maximum |
50 mm (2 in) |
25 mm (1 in) |
4.5 N (16 oz) |
11 N (40 oz) |
| |
Displacement between positions |
| 2 - position |
3 - position |
| Minimum |
30° |
17° |
| Maximum |
80° |
40° |
| Desired |
|
25° |
| |
Separation |
| Single finger operation |
S
Single finger sequential operation |
Simultaneous operation by different fingers |
| Minimum |
19 mm
(3/4 in) |
25 mm
(1 in) |
13 mm
(1/2 in) |
16 mm
(5/8 in) |
| Optimum |
50 mm
(2 in) |
50 mm
(2 in) |
25 mm
(1 in) |
19 mm
(3/4 in) |
Reference: 2, p. 93, NASA-STD-3000 239
| Position |
Function |
|
Position |
Function |
| up |
on |
|
up |
open |
| down |
off |
|
down |
close |
| |
|
| up |
activate |
|
up |
increase |
| down |
deactivate |
|
down |
decrease |
| |
|
| up |
primary |
|
up |
deployed |
| down |
backup |
|
down |
stowed |
| |
|
| up |
automatic |
|
|
|
| down |
manual |
|
|
|
Reference: 1,
p. 4.9-12, NASA-STD-3000 240
9.3.3.3.8 Push button Design Requirements
{A}
Requirements for the design of push-button controls are provided below.
(Refer to Paragraph 9.3.3.3.15, Legend Switch Design Requirements, and
9.3.3.4, Computer Input Devices, for additional information on push-button devices.)
a. Activation:
1. Latching push button (push-on, lock-on) - The button displacement. Activation shall be indicated by a sudden drop in resistance and, if possible, an audible click.
2. Momentary push button (push-on, release-off) - Activation shall be indicated by positive feedback.
3. Alternate Action push button (push-on, push-off) - Activation shall be indicated by a sudden drop in resistance, an auditory click, and an associated display action.
4. Touch Sensitive (nonmechanical) - Activation shall be indicated by positive feedback.
b. Resistance - The resistance of push-buttons to movement shall be 2.78 to 23.63 N (10 to 85 oz). The nominal force-resistance value shall be determined by the particular application and the environment in which it is operated.
c. Dimension:
1. The standard shape of push-buttons shall be rectangular.
2. Round push-buttons shall be used when dictated by special functional or hardware considerations.
3. When a push button surface is not concave, the surface shall provide a high degree of frictional resistance to prevent slipping.
4. T he height and width (or diameter, as applicable) of push-buttons shall be 2 cm (0.75 in.) minimum and 4 cm (1.50 in.) maximum.
5. The illuminated area of push button signal lights shall not be less than 3 cm2 (0.40 in 2) and not greater than 10 cm2 (1.5 in.2).
d. Displacement:
1. Momentary push-buttons shall have a total displacement of 0.32 to 1.84 cm (0.125 to 0.725 in.).
2. Latching push-buttons shall have a total displacement of 0.64 to 1.84 cm (0.250 to 0.725 in.).
3. Alternate action push-buttons shall have a displacement of 0.32 to 1.84 cm (0.125 to 0.725 in.).
4. Pre-travel shall be 0.32 to 1.52 cm (0.125 to 0.6 in.).
5. Over-travel shall be 0.32 cm (0.125 in.) maximum.
9.3.3.3.9 Foot-Operated Switch Design Requirements
{A}
Design requirements for foot-operated switches are provided below.
a. Use:
1. Foot-operated switches shall be used only where the crewmember is likely to have both hands occupied when switch activation may be required, or when load sharing among limbs is desirable.
2. Because foot-operated switches are susceptible to accidental activation, their uses shall be limited to noncritical or infrequent operations such as press-to-talk communication.
3. Foot-operated switches shall be compatible with the restraint system being employed.
b. Operation:
1. Foot-operated switches shall be positioned for operation by the toe and the ball of the foot rather than by the heel.
2. Foot-operated switches shall not be located so near an obstruction that the crewmember cannot center the ball of the foot on the switch button.
3. A pedal may be used over the button to aid in location and operation of the switch.
4. Foot-operated switches shall be compatible with crewmember footwear.
c. Feedback - A positive indication of control activation shall be provided (e.g., snap feel, audible click, associated visual display).
9.3.3.3.10 Pedal Design Requirements
{A}
Design requirements for pedals are provided below.
a. Control Return:
1. Except for controls that generate a continuous output (e.g., rudder controls), pedals shall return to the original null position without requiring assistance from the crewmember (e.g., brake pedal).
2. For pedals in which the operator may normally rest the foot on the control between operations, sufficient resistance shall be provided to prevent inadvertent activation of the control (e.g., accelerator pedal).
b. Pedal Travel Path - The travel path shall be compatible with the natural articulation path of the operator's limbs (i.e., thigh, knee, ankle) for the gravity condition under which the control will be used.
c. Nonslip Pedal Surface - Pedals shall be provided with a nonslip surface.
9.3.3.3.11 Rocker Switch Design Requirements
{A}
Design requirements for rocker switches are provided below.
a. Positive Indication - An indication of control activation shall be provided (e.g., snap feel, audible click, associated or integral light).
b. Dimensions, Resistance, Displacement, and Separation - Dimensions, resistance, displacement, and separation between centers of rocker switches shall conform to the criteria in
Figure 9.3.3.3.11-1. Resistance shall gradually increase, then drop when the switch snaps into position. The switch shall not be capable of being stopped between positions.
c. Orientation:
1. Where practicable, rocker switches shall be vertically oriented.
2. Activation of the upper wing of a rocker switch shall turn the equipment or component on, cause the quantity to increase, or cause the equipment or component to move forward, clockwise, to the right, or up.
3. Horizontal orientation of rocker switches shall be employed only for compatibility with the controlled function or equipment location.
 |
| |
Dimensions |
Resistance |
| W, Width |
L, Length |
| Minimum |
6 mm (1/4 in) |
13 mm (1/2 in) |
2.8 N (10 oz) |
| Maximum |
|
|
11 N (40 oz) |
|
Displacement |
Separation
(center-to-center) |
| H, Ht, Depressed |
A, Angle |
S (bare hand) |
| Minimum |
3 mm (1/8 in) |
30° |
19 mm (3/4 in) |
Reference: 2, p. 96; NASA-STD-3000 241
9.3.3.3.12 Push-Pull Control Design Requirements
{A}
Design requirements for push-pull controls are provided below.
a. Handle Dimensions, Displacement, and Clearances - Handle dimensions, displacement, and clearances for push-pull control handles shall conform to criteria in
Figure 9.3.3.3.12-1.
b. Rotation:
1. Except for combination push-pull/rotate switch configurations, push-pull control handles shall be keyed to a nonrotating shaft.
2. When the control system provides a combination push-pull/rotate functional operation using a round style knob, the rim of the knob shall be serrated to denote (visually and tactually) that the knob can be rotated, and to facilitate a slip-free finger grip.
c. Detents - Mechanical detents shall be incorporated into push-pull controls to provide tactile indication of positions.
d. Action of push-pull controls shall be:
1. Pull towards the operator for ON or activation; push away for OFF or deactivation.
2. Clockwise for activation or increasing function of combination pull/rotary switches.
e. Resistance - Force for pulling a panel control with fingers shall be not more than 18 N (4 lb), for pulling a T-bar with four fingers shall be not more than 45 N (10 lb).
| Configuration example |
Application criteria |
Design Criteria |
| Dimensions |
Displacement |
Separation |
.gif) |
Push-pull control, low resistance, for
two-position mechanical and/or electrical systems
Alternate three position plus rotary function acceptable for
application such as vehicle headlight plus parking lights, panel and dome
lights provide serrated rim
|
D, min dia
19 mm
(3/4 in) |
C, min clearance 25 mm
(1 in)
Add 13 mm (1/2 in) for gloved hand
|
|
25 ± 13 mm (1 ± 1/2 in)
minimum between pull positions 13 mm (1/2 in)
|
S, minimum space between 38 mm (1-1/2 in)
Add 13 mm (1/2 in) for gloved hand
|
.gif) |
Alternate handle; miniature electrical panel
switch only. Avoid glove use application |
