The primary usefulness of helicopters shows in missions where regular aircraft cannot be used, especially HEMS
(Helicopter Emergency Medical Services). This might be due to requirements for landing in unprepared areas
without dedicated runway structures, and an extended
y to more than one previously unprepared
target. One example of such missions are search and rescue operations. An important task of such a mission is to
locate a proper landing spot near the mission target. Usually, the pilot would have to evaluate possible landing
sites by himself, which can be time-intensive, fuel-costly, and generally impossible when operating in degraded
visual environments. We present a method for pre-selecting a list of possible landing sites. After specifying the
intended size, orientation and geometry of the site, a choice of possibilities is presented to the pilot that can
be ordered by means of wind direction, terrain constraints like maximal slope and roughness, and proximity
to a mission target. The possible choices are calculated automatically either from a pre-existing terrain data
base, or from sensor data collected during earlier missions, e.g., by collecting data with radar or laser sensors.
Additional data like water-body maps and topological information can be taken into account to avoid landing in
dangerous areas under adverse view conditions. In case of an emergency turnaround the list can be re-ordered
to present alternative sites to the pilot. We outline the principle algorithm for selecting possible landing sites,
and we present examples of calculated lists.