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:
- Landings done by Search and Rescue helicopters on a mission to assist in case of an emergency situation on ground.
- 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.
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.
The proposed SELIAT landing information service aimed at enabling the pilots to increase their safety and to improve their efficiency during flight operations. Having the information available in the cockpit, the pilots benefit from:
- Rescue missions’ operation time reduction resulting in alleviation of loss in terms of human lives and economy.
- In-time decision making, improving the possibility of a successful emergency landing.
- Reduction of the pilots’ dependency on ground support.
Available services in the cockpit provide only official landing sites, i.e. heliports. Although they include terrain information for collision detection, this information is too coarse for identifying suitable landing sites. Among glider pilots, there are online catalogues with off-field landing information in use where the accessibility during flight is not yet solved adequately. Moreover, there exist other technologies for on-board acquisition and processing of landing information that are researched for use in off-field landings. But they involve expensive and heavy sensing equipment to be mounted on the helicopter. In addition, they cannot help identifying landing sites in advance, before the helicopter has reached the location.
Consequently, SELIAT addressed a light weight solution that overcomes problems of existing systems. It incorporated innovative technologies, e.g. digital elevation models (DEMs) with a high resolution that has not been provided to aviation yet.
The architecture for providing the SELIAT service has been described with the figure below. Therein, the service is subdivided in three sections. The first section covers the acquisition of the required input data, the second section covers the production and provision of relevant geo-information, and the third section covers the communication of the information product to the users.
- The different input data sources address all the relevant information needs. These data sets incorporate high-resolution optical satellite data, radar data products, airborne laser scanning data, weather information from sensor networks, and information from existing databases. The high-resolution images and surface models of MAVs are also included. All these data products are integrated into a database for the analysis.
- The second section consists of the SELIAT core service infrastructure. It includes a processing unit for analyzing the input data and a database cluster for storing the landing site geoinformation product. The product is provided in several appropriate formats through the wide area network (WAN).
- The third section displays the transfer of the product to the end user devices, i.e. SELIAT Mobile and SELIAT Mission Control & Planning Centre (MCPC). In addition to the wide area network connection, the data can be transferred with satellite communication (SatCom) and mobile Telecommunication. Global Navigation Satellite Systems (GNSS) onboard of the aircraft will be used for identifying the relevant spatial extent of the required data.
- For a good acceptance of our emergency landing information service, the service was designed to suit best the pilots’ requirements while staying within the restrictions of other stakeholders in the aviation domain.
- For a technically sound service, the best suitable combination of state-of-the-art technologies was identified that was beneficial and technically reliable.
- For a financially sustainable service, the expected service costs had to be acceptable to the user organisations to integrate the service in their operations.
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.