Home' RTCA Documents for Review : Addressing Human Factors/Pilot Interface Issues Contents 31
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consistency among propulsion, flight, navigation, and other displays and
indications used on the flight deck. If red and yellow/amber are proposed for non-
alerting functions, coordinate early with the certification authority to discuss
whether there is an operational need and how the colors used will be validated to
determine whether it adversely affects flightcrew response to alerts.
When designing displays and developing an alerting philosophy, the use of a color
philosophy has ensured a consistent use of color. One way to ensure a consistent
flight deck color philosophy gets applied to added products is to provide a well-
documented color philosophy to the equipment supplier as early as possible in the
design process. By providing this color philosophy at the beginning, the equipment
can be modified to comply during development. This can be very difficult to
change in the final stages of certification and will typically drive late software
changes if not found early in the design process.
Consider the discrimination of colors under all viewing conditions.
The use of redundant color coding has been used where the ability to discriminate
between the information is important. Research data indicates that redundant
coding improves recognition, identification and interpretation of displayed
The following documents provide design guidance for color:
o AC 25-11(), Electronic Flight Deck Displays
o AC 25.1322-1, Flightcrew Alerting, provides guidance for the design and
approval of flightcrew alerting functions for Part 25
o SAE Aerospace Recommended Practice (ARP) 4032(), Human Engineering
Considerations in the Application of Color to Electronic Aircraft Displays
The word "symbology" is defined as a set of symbols used in a system. The number of
symbols used by a system can grow as display capabilities increase and there is a desire to
display more information. The large number of symbols and multiple use of symbols on
some flight decks increase the potential for interpretation errors and the difficulty in
integrating the information, and both could lead to inappropriate pilot action.
Specific Certification Issues
Consistency in symbol appearance: Symbols in a newly installed system that are
different than symbols representing the same information depicted elsewhere in
the flight deck created confusion.
o Symbols shown on head-up displays were not compatible with the symbols on
head-down displays and required additional effort to understand the aircraft
state during head-up / head-down transitions.
o New systems shared some of the same symbology with other systems on the
flight deck, but the symbology meant something different for that application.
Insufficient information (absence of primary flight symbology) on head-up display
(HUD): In a previous certification project, the HUD intended function was to
provide primary flight information for use as a PFD but the HUD did not present
the required information for a full-time PFD.
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