In March this year, the European Geostationary Navigation Overlay System (EGNOS) became fully operational and certified for aviation applications. This Satellite Based Augmentation System (SBAS) improves the performance of GPS receivers. It provides an immediate opportunity for airspace users to benefit from increased integrity and position performance, in particular for approach operations. This performance improvement is delivered without any additional airport ground equipment. Therefore it can increase the reliability and continuity of service within low visibility conditions to remote and less equipped airfields and heliports.

For helicopter operations the benefits are significant, as EGNOS provides the capability to realise instrument approach procedures to airfields and helipads currently without. Over the past few years flight trials have been undertaken to explore the operational and technical benefits that EGNOS can bring. An example is the EU part-funded project HEDGE (Helicopters Deploy GNSS in Europe), a consortium led by Helios. HEDGE has been flight trialling new instrument approach procedures to take advantage of the new capabilities and performance afforded through EGNOS constellations. This has focused on three different approaches, namely:

• APV SBAS (LPV) approaches - straight-in approaches in which the final approach segment is aligned with the runway
• SBAS enabled PinS (Point-in-Space) approaches - in which the helicopter flies to a point-in-space(defined as the missed approach point) and from this point navigates visually
• SBAS Offshore Approach Procedures (SOAP) - a new approach concept validated through HEDGE supporting offshore operations around oil and gas platforms

Of these approaches, the PinS approach potentially provides the most benefit to HEMS (Helicopter Emergency Medical Service) Helicopter Emergency Medical Service) operations.

Flight trials were performed at Interlaken by REGA Swiss Air-Ambulance. During the winter months in the Swiss Alps a relatively thin layer of cloud is quite common – although good conditions still exist above and below it. Without PinS two choices exist for the recovery of a person in need of a HEMS helicopter in this case

• The HEMS helicopter rendezvous with an ambulance above the cloud layer for recovery by road, or
• The helicopter descends through the clouds, currently performed as a VFR descent through openings in the cloud layer.

Consequently, there is no guarantee of a successful descent resulting in increased workload for the HEMS flight crew as well as a delayed “Time to treatment” for the patient. However, the SBAS enabled PinS procedure overcomes this obstacle by providing instrumented guidance through the clouds layer to the visual conditions below. This not only provides savings in fuel and aircraft maintenance to the HEMS operator, but also expedites the transfer of patients to the hospital - potentially saving lives.

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