Ergonomics Experiment Research on Visual Characteristics of
Head-Up-Display Failure Warning
Authors: guoqiang Sun , wu Xu 
Published: February 2023

With the gradual adaptation of HUD (Head-Up-Display) in civil
transportation, it was normal for civil pilots or even drivers to use it.
Howev-er, any failure warning of airplane HUD was so fatal that required
pilot to search for it immediately and make correct response to recover. As
the pri-mary indicator of HUD warning, failure flag was well-designed
especially in visual coding, which directly affected pilot’s recognition and
acquisition of warning information. This research developed ergonomics
experiment of HUD simulation interface and designed character size of
failure flag as ex-periment variable. The participants were required to
perform signal detection task and response to signal (warning occurred) or
noise (no warning) accord-ingly. Therefore, both sensitivity and response
bias were measured to analyze visual characteristics of failure flag and its
influence on HUD warning.The mechanical failures of airplane were mainly
caused by unreasonable mecha-nism structures or improper system operations,
which was excluded from conse-quence of any manually operation or other
outside factors . And the failure flag was shown on HUD when the sensor
status was unavailable and the same parameter from different sources did not
match . The representative mechanical failure flags were included with
indicated airspeed warning, barometrical altitude warning, head-ing warning
and ground proximity warning. Moreover, HUD failure warning could be
displayed in various channels of visual, auditory and tactile manners, and
the first two were most widely used channels . The visual channel of HUD
failure warning was normally designed in visual coding technology, which was
involved with size, position, salient of blink or textbox frame. And the
auditory channel focused on volume and tone of warning voice. Specifically,
the minimum character size of failure flag was 1/200 of the visual field
distance, i.e., at least 0.18-inch character was required to be shown on HUD
at distance of 36-inch away. In addition, the aspect ratio for English
letter was required as 3:5 , and its typeface was selected as Arial . To
analyze the effect of visual coding on failure flag on HUD, this research
firstly developed HUD interface simu-lation, and then carried out ergonomics
experiment to validate the influence of char-acter size.3.2Experiment
InterfaceAs shown in Fig.3, the experiment interface was displayed on
17-inch computer screen with visual distance of 60cm. The screen resolution
was 1440×900 and aver-age luminance was 120cd/m2. The participants were
required to interact with exper-iment computer through normal mouse and
keyboard. The HUD interface was simu-lated on GL Studio platform, and the
experiment was realized using C++ and net communication technology on Visual
Studio 2012. Each interaction with experiment computer was recorded and
output when the experiment task was completed.3.4Experimental TaskThe
participants were required to perform signal detection task during the
experi-ment block, followed by the order of Latin Square fashion. And each
block lasted for ten minutes with interval of five minutes. Moreover, the
failure flag was designed to occur at possibility of 75%, with noise-signal
ratio as 1:3. To response each failure flag, they need to press
corresponding button of W/A/S/D/E on keyboard according to the specific
warning. And SPACE button was expected to be pressed when no warning was
shown.ResultsBoth statistics analysis and signal detection method were used
to process the exper-iment results. First, descriptive statistics was used
to illustrate central tendency and dispersion degree of detection
performance. Then, repeated measured ANOVA was used to examine the effect of
character size. In addition, sensitivity d’ and response bias were processed
to evaluate the influence of failure warning based on signal detection
theory.