IEEE - Aerospace and Electronic Systems - April 2021 - 28

Virtual Cockpit Instruments-How Head-Worn Displays Can Enhance the Obstacle Awareness of Helicopter Pilots

Figure 10.
Readability of the Virtual Cockpit Instrument on the JEDEYE.
(Boxplots show median (dot/circle), 25th and 75th percentiles (filled
rectangle), and outliers (x markers) with whisker length 1.5 IQR.)

Figure 9.
Overall rating of the presented display sets. (Boxplots show
median (dot/circle), 25th and 75th percentiles (filled rectangle),
and outliers (x markers) with whisker length 1.5 IQR.)

study indicated that this was a good size. A few would prefer to slightly increase the VCI.
The virtual instruments are see-through displays
where the symbology is superimposed onto the reality.
Therefore, the readability of the VCI is not only a matter
of size and resolution but also of the instrument's background. Depending on the VCI positioning mode, the
background can be uniform and constant or heterogeneous
and ever-changing.
The first study compared several positioning options. It
found that the reality behind the VCI had a strong negative
impact on the readability when the VCI was located at the
HUD position. The subjects explained that they had major
problems reading the symbology since the horizon crossed
the VCI in the background. The differences between the dark
ocean in the lower half and the bright sky in the upper half of
the display caused strong contrast issues. On the contrary, the
VCI projected onto the dark instrument panel (AircraftFixedHDD) performed best. Nevertheless, the most important finding was that all head-coupled variants caused no or only weak
readability issues-despite the fact that the instrument background was continually changing during head movements.
A major question of the second experiment was
whether the good readability of the head-coupled variants
on the VR goggles could be confirmed with an actual seethrough HMD. As illustrated in Figure 10, this can be
answered with yes: The participants acknowledged that
the underlying reality had no negative influence on the
readability of the VCI.
The pilots are not only interested in reading the VCI but
also want to monitor the real world. Thus, it not enough to
guarantee that the underlying reality does not degrade the
readability of the VCI. Vice versa, we also have to ensure
that the VCI being overlaid onto the reality does not disturb
the pilots' out-the-window view. The participants reported
that the VCIs did not clutter the natural vision in most conditions. Only the VCI positioned in flight direction above
the panel (AircraftFixed-HUD) masked too much of the
central, forward FOV and disturbed the pilots' out-the-window view during the approach.
In summary, the results of both studies show that the
VCI size and position should be chosen carefully because
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this may have strong effects on readability and clutter. The
setups for study II (Mixed, Head-Fixed) were found to be
reasonable choices in that matter.

COMPARISON OF VCI POSITIONING OPTIONS
As described in the section " Virtual Cockpit Instruments
for Obstacle Awareness & Collision Avoidance, " a major
benefit of VCIs is their flexibility regarding position and
frame of reference. In our first VR-based study, we tested
a large number of possible positioning options and
selected the most promising variants. The details of this
assessment are presented in [6]. In summary, the conditions Mixed-HDD-Below and HeadFixed-Below were the
preferred variants, closely followed by the more conventional AircraftFixed-HDD mode. Consequently, the follow-up study took a closer look at these preselected
positioning options. The remainder of this results chapter
also focuses only on these most relevant VCI modes.
The pilots tested two different positioning modes for the
VCI on the JEDEYE. In the VCI-HeadFixed condition, the
VCI was head-fixed throughout the whole flight. It remained
inside the pilots' FOV all the time. By contrast, in the VCIMixed variant, the VCI was located at an aircraft-fixed position beside the instrument panel during the approach phase.
As soon as the pilot transitioned to the hover phase, the VCI
switched to a head-fixed position similar to VCI-HeadFixed.
When asked about their preferred positioning mode, two
pilots chose VCI-HeadFixed, three favored VCI-Mixed, and
the remaining two stated that both are equal.
To further assess the Mixed mode, the participants
were queried on the helpfulness of the altering VCI behavior in the two phases of the hover task. Figure 11 confirms
that this was seen helpful. Also, the VCI position that we
chose for the approach phase-right of the instrument
panel [cf. Figure 2(a)]-was satisfying for the majority of
the pilots.

FLIGHT PERFORMANCE
In addition to the pilots' subjective ratings, we also evaluated which effects the VCI had on the flight performance.
First, we looked at the accuracy of the hover maneuver
that the participants performed in both studies. Second,
we checked the performance achieved during the landing

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IEEE - Aerospace and Electronic Systems - April 2021

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