Home' RTCA Documents for Review : Addressing Human Factors/Pilot Interface Issues Contents 48
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The controls covered in this section represent the primary system interface for inputting
data and selecting system options. Over the years, the number and variety of controls has
grown. Today, flight decks may contain a range of controls such as knobs, buttons,
switches, keyboards, cursor control devices (CCDs), touch screens, and speech controls.
Regardless of the type of control, the goal is to design a means for interacting and providing
input to the system that pilots can identify, understand, and operate successfully. This
section will discuss a variety of control-related issues including feedback, control labeling,
functionality, and touch screens.
Whether visual, tactile, or auditory, control feedback provides the pilot with an indication
that a control input has been received. Typically, traditional, physical controls (e.g., buttons
and switches) provide tactile feedback upon actuation, while soft/virtual controls (e.g.,
graphical user interface (GUI) that uses a cursor control device to activate soft controls on
a display or touch user interface that requires fingertip pressure to activate soft controls on
a display) rely more on visual feedback to indicate actuation. Without effective feedback,
workload and errors are likely to increase. All types of controls need to consider where,
when, and how feedback gets provided to the flightcrew.
Specific Certification Issues
Increasing the distance between the control and its visual feedback cues has led to
increased flightcrew workload and errors (for example, entering data on an aft
pedestal mounted keypad or overhead panel and confirming the data entry on a
Input latency issues have resulted in errors, due to lack of feedback. For example,
a keypad entry display lagged far enough behind the keypad entry input that it led
the pilot to think the entry was not accepted and led to the entry being repeated.
Overhead panels that implement a dark, quiet flight deck philosophy may
implement physical annunciator switches that have no clear indication of being
raised or lowered, making that distinction difficult under some lighting conditions.
Approved Design Examples
A “scratchpad” or display area has been added just below some physical keyboards
to provide immediate feedback to the flightcrew of what data has just been entered
with the keypad so they can review it prior to activating.
A symbol that has been added to the display to indicate to the flightcrew that the
system has received the input, and is still performing the action.
For controls, applicants have used feedback such as color change, a change in
brightness, a change in text size, text boxing, or highlighting to indicate that the
control has been selected. Similarly for touch and graphical user interfaces,
applicants have used the blooming of a button, the appearance of a letter above a
finger position on a virtual keyboard, or an icon change to show that the control is
active, are both approved examples of control feedback. See the examples in
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