Home' RTCA Documents for Review : Addressing Human Factors/Pilot Interface Issues Contents 33
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expected operational conditions of intended use (e.g.,
meteorological conditions (IMC) in high crosswind conditions).
o SVS systems that presented a compressed image with a wide field of view on
a small screen led to objects in the image appearing farther away from the
aircraft than they actually were. The presentation of aircraft attitude on a
compressed pitch scale on synthetic scene led to lack of precise flight path
o Obstacles on SVS displays that were presented using the same scaling as other
features led to pilots overlooking them without a means to draw their attention
to the potential threat.
Temperature compensation: Failing to compensate for temperature differences led
to errors in the depiction of paths on the flight management system and of the
imagery on an SVS. For both these systems, if the altitude is left uncompensated
during cold weather, the aircraft will be closer to the ground than depicted.
Navigation Source: When multiple navigation sources were presented on the same
PFD, identification of which symbol set coincided with which navigation source
was confusing. For example, in a system where a global positioning system (GPS)
derived highway in the sky (HITS) was presented as “supplementary information”
during an instrument landing system (ILS) approach , it was difficult for pilots to
discern if the HITS was the primary glide slope depiction rather than the raw data
presented on the glide slope deviation indicator.
Approved Design Examples
To mitigate the presentation of off-scale information, applicants have changed
off-scale symbols to a “ghost” symbol, shifted the display field of view, or
presented information as a track-centered display. Indicating target bugs set off
scale has been implemented by using cues such as arrows or parking half bugs at
the edge of the scale, pointing in the target bug direction. To prevent synthetic
vision symbology from being presented outside the display range at unusual
attitudes, manufacturers have used a dynamic pitch scale that presents a larger
pitch range to accommodate unusual attitudes and then returns to the normal pitch
range when the attitude is again within normal limits. For tape displays of altitude
and speed, target values have been displayed above, or near the altitude / speed
tape for additional awareness of the target in addition to the target bug indication.
On SVS displays obstacles that are in close proximity to the current flight path
have been displayed more prominently than more distant obstacles. This
minimizes visual clutter, but also enables the perception of the potential threat in
time for the flightcrew to make corrective actions, if required.
Applicants have proposed new, specialized symbology for rotary wing
applications (e.g., hover displays for search and rescue or station keeping, rig
approach, steep approach, Category A takeoff profiles, etc.). An example hover
display is shown in Figure 3-4 below; the display provides the pilot with
information regarding drift direction and ground speed. Depending on how the
display functions, the pilot either flies the green circle to the aircraft or aircraft to
the green circle to stop the drift and zero the groundspeed. If integrated with the
auto flight and guidance system, many hover modes provide the pilot with steering
cues to waypoints or targets and position/velocity hold functions.
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