Home' RTCA Documents for Review : Addressing Human Factors/Pilot Interface Issues Contents 35
© 2017 RTCA, Inc.
When designing new symbology that goes beyond what is covered by existing
regulations, the applicant needs to be prepared to provide data validating the use
of symbology that has not been seen before by the certification authority to ensure
that the symbology is understandable and usable (14 CFR 25.1302 Installed
systems and equipment for use by the flightcrew and AC 25.1302-1 Installed
Systems and Equipment for Use by the Flightcrew).
To avoid extensive flight test by certification authorities and a protracted
certification process, ensure that the relationship between the aircraft’s heading
angle and track angle is readily recognizable by the pilots under all expected
operational conditions associated with the intended function (e.g
, under high
Ensure that obstacles that are relevant to the current flight path are presented such
that the pilot can perceive them with enough time to determine any corrective
Consider minimum symbol / text size based on the viewing distance from the
pilots’ design eye position. SAE ARP4102/7 Electronic Displays provides
recommendations on acceptable font sizes for the distance required and how to
quantitatively define these requirements during engineering design.
The report, Survey of Symbology for Aeronautical Charts and Electronic Displays:
Navigation Aids, Airports, Lines, and Linear Patterns (DOT/FAA/AR-07/66;
DOT-VNTSC-FAA-08 -01), documents symbology in use by manufacturers and
Labels identify controls, symbols, and data fields and indicate their function or the result
of their activation. Carefully worded labels help the pilot assimilate the information
quickly. Additionally, consistency in label terminology across display systems and
mediums (e.g., electronic displays) reduces the time needed to search for, and interpret a
given function. If labels are poorly designed, the pilot may not be able to determine what
is being controlled, what the purpose of a display element is, or what data to enter.
Specific Certification Issues
Inconsistency in labeling between different display types on the same flight deck
has led to confusion. For example, APPROACH, APPR, and APR have all been
used as a label for the term “Approach” on the same flight deck but displayed
differently in the caution and alerting system (CAS) message, multi-function
control display unit (MCDU), and PFD flight mode annunciator, all referencing
the same phase of flight. There have also been many cases where labels used in the
aircraft differed from the labels in the Aircraft Flight Manual (AFM), which
slowed down their ability to work through the procedure.
Use of abbreviations or acronyms that are not common, referenced from standard
abbreviation sources, or that are not easily recognizable have led to
misinterpretation, confusion, and errors. In some cases, additional letters have been
included to make the label more intuitive but this created a new abbreviation for
pilots to remember.
The font size was not appropriate (e.g., small fonts were unreadable at long
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