IEEE - Aerospace and Electronic Systems - April 2021 - 21

Ernst et al.

Figure 2.
Illustrations of selected VCI modes during different phases of an approach and hover maneuver at an offshore wind turbine. The images were
generated on VR goggles (study I) and demonstrate the pilot's view through a monochrome green, see-through HWD (study II). Details
about the studies and the various display variants are given in the section " Evaluation Method. " (a) Aircraft-fixed VCI during the approach
phase: The VCI is positioned right of the instrument panel. The image also shows the head-up PFD and the symbology displayed on the
PMD (PFD and OAWD). This display setup corresponds to the display variant VCI-Mixed in study II. (b) Head-fixed VCI during hover: The
VCI follows the pilot's head movements. Here, the pilot looks to the right towards the wind turbine. The VCI remains within the field of
view. This corresponds to the following experiment conditions: Mixed-HDD-Below and HeadFixed-Below in study I as well as VCI-HeadFixed and VCI-Mixed in study II.

symbology. Its distinctive feature is the drift visualization
via the pilot's peripheral vision. Finally, it should be
noted that this list is not exhaustive as many other corporations and research institutes developed similar systems
(e.g., [24],[25]).
Despite all benefits, the presentation of obstacle
information as conformal overlay entails two major
issues: First, the 3-D perspective comes with an uncertainty of locations and distances ( " line of sight
ambiguity " [26]). Second, the egocentric perspective is
incomplete since the pilots cannot see what is behind
them. Especially when operating in confined areas like
urban spaces or near offshore constructions, obstacles
can be located behind the helicopter, out of the pilot's
view. This may cause hazardous situations where
tail or rotor strikes can occur [9],[12]. Hence, this
article proposes the additional integration of an
orthogonal, 360 top view with obstacle information
into the HWD.

VIRTUAL COCKPIT INSTRUMENTS FOR OBSTACLE
AWARENESS AND COLLISION AVOIDANCE
This work shows how existing HWD symbol sets can be
enhanced by adding VCIs. Figure 2(a) shows an exemplary implementation: A conventional head-up PFD symbology is complemented by a virtual navigation display
that is also generated by the HWD. Information that is
typically displayed on conventional PMDs is thereby
moved to the HWD. In the section " Integration With
State-of-the-Art Head-Up Symbology, " the depicted
APRIL 2021

symbol set is further expanded by DLR's visual conformal landing symbology.

VIRTUAL COCKPIT INSTRUMENTS
The prime advantage of VCIs is their independence from
the flat panel screens of the cockpit. Conventional cockpit instruments are bound to the location, the size, and
other specifications of the panel display rendering them.
In contrast, a VCI can be created anywhere in the virtual
space around the pilot. Its size and position can be
adapted according to the requirements of the present
task or flight phase. If it is currently not required, it can
simply be hidden, which avoids clutter and clears the
pilot's vision for the relevant information. If more display area is needed, the VCI can easily be enlarged or an
additional VCI can be activated; options that are not
available on a conventional flight deck with its inflexible
panel display setup. This creation of additional display
space is especially relevant for small helicopters like the
ones often used for rescue medical services and in offshore wind farms because they have a very limited number of PMDs and cannot easily be retrofitted due to
space constraints.
This great freedom and flexibility leads to the question: Where should such a virtual instrument be placed so
that it creates a benefit for the pilot? Naturally, the answer
to that question highly depends on the application scenario
and on the actual VCI display contents. Having that in
mind, we will start by presenting a comprehensive set of
possible VCI positioning modes. In the rest of the article,

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IEEE - Aerospace and Electronic Systems - April 2021

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