System Offers Higher Degree Of Accuracy Than GPS

Successful trials have recently been conducted at Lausanne, Switzerland, using the European Geostationary Navigation Overlay Service (EGNOS) to guide a helicopter as it approached and touched down at an emergency medical service landing pad.

The adaptable, go-anywhere characteristics of helicopters make them ideal for emergency services, but when visibility is poor their operations are limited by aviation regulations. The accurate position reporting and navigation system integrity checking offered by EGNOS will be a vital service for anywhere, anytime rescue services.

The trials were performed by Eurocopter, using its EC155 experimental all-weather helicopter (type shown below). The trial was coordinated by skyguide, the Swiss air navigation service provider, and consisted of a number of validating approaches performed by the HTT to a Helicopter Emergency Medical Services (HEMS) pad located on the roof of Lausanne University Hospital, according to the European Space Agency.

The test team was hosted in Lausanne's La Blécherette aerodrome by the Swiss medical air rescue agency Schweizerische Rettungsflugwacht - Garde Aérienne Suisse de Sauvetage - REGA who also participated in the flight tests.

The trial approaches were designed by skyguide for 6 degree and 9 degree approach angles. Initial feedback from the test pilots indicates that, despite of the steepness of the approaches - the standard approach angle is 3 degrees - they are easy to fly because of EGNOS' three-dimensional guidance. Vertical guidance for the pilot is a major advantage EGNOS offers over standard GPS.

The increased approach angles also reduce noise nuisance on the ground as the helicopter can remain at high altitude until it is closer to its destination before commencing its final descent. In addition, a steeper descent angle reduces the noise generated by the rotor blades as the craft nears the ground.

The implementation of instrument approaches for HEMS operations will allow the emergency services to continue their operations in weather conditions that would otherwise ground their helicopters, said the ESA.

The trials were performed as part of the GNSS Introduction in the AviatioN secTor (GIANT) project. GIANT is a European Commission Sixth Framework Program (FP6) project with the aim of supporting the introduction of EGNOS and Galileo services into the aviation market while demonstrating to the responsible authorities that the required safety levels are achieved.

The helicopter trials follow on from the fixed-wing EGNOS/GIANT trials held at Valencia, in Spain, during late 2006. Additional GIANT flight trials will be performed in 2007 at other European airports and on an oil rig in the North Sea.

EGNOS is a joint program of the European Space Agency, the European Commission and Eurocontrol. EGNOS is made up of a network of more than 40 elements all over Europe that collect, record, correct and improve data from the US Global Positioning System (GPS).

The modified signals are then relayed via geostationary satellites to user's terminals, offering a positional accuracy of better than six and a half feet, compared with 50 to 65 feet for GPS alone. In addition, EGNOS gives a guarantee of quality for these signals that GPS does not provide.

FMI: www.eurocopter.com, www.rega.ch/en/start_en.aspx, www.esa.int