IEEE - Aerospace and Electronic Systems - April 2021 - 22

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

Figure 3.
Overview of the four VCI positioning modes (Aircraft-Fixed, Aircraft-Related, Mixed, and Head-Fixed) and the respective instrument positions. Aircraft-Related and Mixed comprise submodes depending the pilot's viewing direction.

these concepts will then be applied to helicopter offshore
scenarios in order to answer the stated question-for this
specific case.
First of all, the display designer must choose a suitable
frame of reference for the VCI. Conventional PMDs are-
for obvious reasons-always fixed to the aircraft frame.
Their position relative to the aircraft does not change;
they are " aircraft-fixed. " If the pilot looks somewhere
else, the displays get out of sight. In a previous publication [4], we also implemented the virtual instruments like
this. However, the VCI approach offers more options: A
VCI can also be attached to the head-fixed frame of reference. This means that it will strictly follow the pilot's
head movements and always remain in sight [cf. Figure 2
(b)]. Figure 3 provides a schematic overview of the developed VCI positioning options, including these two basic
variants (Aircraft-Fixed, Head-Fixed) but also combinations and derivatives of them (Aircraft-Related, Mixed).
For example, the VCI can primarily have an aircraft-fixed
position but every time the pilot looks to the side, the VCI
becomes head-fixed to remain visible. We call this the
Mixed mode. Finally, the Aircraft-Related mode has a
similar switching behavior between two submodes. However, instead of the " head-fixed " submode, it features a
" clipped " state. Here, the VCI appears at one of the four
borders of the field of view (FOV).
As shown by the rhomboids in Figure 3, the VCI
can-of course-have different positions within the chosen frame of reference. Within the aircraft-fixed frame,
the straightforward way is to place the VCI where a conventional cockpit instrument would be, i.e., in the panel
area. This variant is called " HDD " (head-down display).
Furthermore, we implemented a " HUD " position. Here,
the VCI is located above the instrument panel in the windshield area where a conventional HUD would be mounted.
In addition to these familiar options, we also placed the
VCI on the right of the instrument panel ( " beside panel " ). Figure 2(a) shows how this mode appears to the
pilot looking through the HWD. Regarding the headfixed position, we realized only one position where the
VCI is located " below " the pilot's viewing direction
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(i.e., in the lower center of the HWD screen).
Figure 2(b) illustrates this variant during an offshore
hover maneuver. More information on these positioning options can be found in [6].

OBSTACLE AWARENESS AND COLLISION AVOIDANCE
SYMBOLOGY FOR THE VCI
Inspired by the display formats presented by Airbus and
AgustaWestland (cf. " Obstacle Awareness and Warning Systems " ), we implemented a VCI-adapted obstacle awareness
and warning display (VCI-OAWD). It was specifically customized for the usage as a VCI on a see-through display. Furthermore, it was adapted to the monochrome green color of
DLR's flight-certified HWD. Figure 4 shows the two pages
of our VCI-OAWD. The approach page is similar to a conventional navigation display in rose mode. It shows the
approach route, surrounding objects, and various supplemental information, such as the current wind conditions. The
hover page is activated when the helicopter passes a certain
distance to the desired hover position. It provides an orthogonal 360 top view of the near-field including the desired
hover position and nearby obstacles. To improve the pilot's
distance estimation, it renders two circles indicating the main
rotor size and the required safety clearance. Similar to Airbus' RSAS, the area around the ownship is divided into sectors, which are highlighted if an obstacle is detected within
that zone.

INTEGRATION WITH STATE-OF-THE-ART HEAD-UP
SYMBOLOGY
As described in the section " Head-Worn Display Symbology, " a typical HWD is usually filled with various
kinds of symbology. Thus, it is an integral part of our
work to investigate how the proposed VCI concept
works together with already existing symbol sets. To
do so, we integrated the new VCI-OAWD with a standard head-up PFD and with DLR's proven landing

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IEEE - Aerospace and Electronic Systems - April 2021

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