ESA title


  • ACTIVITYFeasibility Study
  • STATUSCompleted
  • THEMATIC AREATransport & Logistics

Objectives of the service

SELIAT stands for the feasibility study Safe Emergency Landing in Alpine Terrain. It has investigated a service in aviation that shall provide geographic information about suitable landing sites to support off-field landings in alpine areas with difficult terrain. This information will be available to pilots in their cockpit. The information may be required either as part of an operation of a search and rescue mission or in case of a technical failure in the aircraft.

Although aviation generally is considered to be very safe, emergency landings need to be performed regularly, either as part of an operation or as in case of a failure in the aircraft. In the context of the proposed study, there were two main categories of emergency landings of interest: 

  1. Landings done by Search and Rescue helicopters on a mission to assist in case of an emergency situation on ground.
  2. Emergency landings of helicopters and small aircrafts e.g. as a consequence of an engine failure. 

In the first case the landing is planned in advance:

  • SELIAT aimed at enabling a pre-selection of potential landing sites and guidance by the integrated flight instruments in order to increase the safety of the operations and to reduce the response time, thereby improving the chances of injured persons on the ground. 

In the second case the landing site has to be selected within seconds during the emergency procedure:

  • SELIAT aimed at providing relevant information about the nearest suitable emergency landing sites within reach of the aircraft (possibly without engine power) as well as providing guidance to reach the selected site, in order to increase the probability of a successful emergency landing. 

In addition to these operationally driven objectives, the application of novel technologies in this context was tested:

SELIAT explored the feasibility of technologies such as micro aerial vehicles (MAVs) as in-situ and possibly near real-time sensors and identified their potential benefits and shortcomings.

SELIAT potential off-field landing sites on EuroNav

Users and their needs

SELIAT was designed as a geospatial aviation product that provides off-field landing sites information to be integrated in cockpit equipment. The study therefore involved avionics and aircraft suppliers. The addressed users in need of off-field landing sites were: 

  • Search and Rescue helicopter operators and pilots
  • Flying clubs for gliders and single-engine aircrafts and pilots

Two scenarios are categorized in which the service was expected to be beneficial, namely in case of a search and rescue mission and in case of an emergency landing. The pilots want to increase their safety and would like to improve their efficiency during flight operations. Therefore, they demanded the most suitable geo-information that may be available. In terms of landing information requirements, the following geographic information was identified to be necessary: 

  • Mission landing sites close to the accident accompanied with their characteristics, e.g. area (length and width), terrain elevation, slope inclination that provide stable and safe ground support for the operation from this site.
  • Emergency landing sites suitable for the kind of the required emergency procedure and within reach of the pilot’s (possibly damaged) aircraft accompanied with their characteristics (depends on cause of forced landing).
  • Flight directions and distance to the site.
  • Weather conditions at the landing site.
  • Surrounding obstacles close to the landing site.
  • For increasing the possibility of successful emergency landing, the information must be immediately available.

Service/ system concept

The service was designed to provide geographic information to pilots about suitable landing sites to support off-field landings. The sites were identified in digital surface models and optical imagery provided by earth observation satellite services and, in a complete production, would cover the area of the Alps. The provided geographic information also included aviation obstacles in the landing approach area surrounding the landing sites. The test service provided the information product to the pilots on sophisticated electronic flight instruments in the cockpit. A web service component was included in the design for a real-time exchange of position information via satellite communication, an option that later was not followed.

Space Added Value

Earth Observation data provided the fundamental inputs for selecting suitable emergency landing sites from high resolution digital elevation models (DEM) and optical satellite imagery. Besides EuroMaps3D, test DEM data was available from the TerraSAR-X / TanDEM-X missions. The optical satellite data comprised primarily Rapideye, but also Landsat 8.

Satellite Navigation was the principle means for measuring precision location and for navigation.

Satellite Communication was an optional means for in-flight communication in emergency situations. 

Current Status

Based on the pilots’ needs for landing information, the SELIAT team designed a service with current technologies of optical satellite data and terrain models. In a proof-of-concept, prototypical maps of potential off-field landing sites were produced. They were successfully tested during a helicopter flight and have received positive feedback from potential users.

The results showed that EO data provides an added value as a comprehensive search tool for the identification of landing sites. Besides the successful testing of data acquisition with Micro Aerial Vehicles, it proved to be more reasonable to exclude this approach to detailed mapping of each identified landing site. Instead, a thorough handling of the uncertainties in the EO-based landing information product leads to the accuracy and reliability that the pilots require in their information.

The adapted service aims at providing information of safe flight corridors for safety-aware flight planning. A planned route will keep the helicopter pilot within reach of emergency landing sites as long as possible.

With this new information product, Salzburg University and its project team plan a demonstration project for further development in order to achieve an operational service.

Status Date

Updated: 13 April 2015