EGNOS is the European Geostationary Navigation Overlay Service. It augments GPS, transmitting information to improve the accuracy, integrity and availability of the user's navigation service. EGNOS is an example of a Satellite Based Augmentation Servive (SBAS). EGNOS provides a high-performance navigation signal that can benefit aviation. Specifically, it offers an approach capability (known as APV SBAS) that is is close in performance to ILS CAT I.
What benefits will HEDGE project bring to the aviation industry?
Helicopter operations can benefit significantly from advanced GNSS (Global Navigation Satellite System) capabilities. HEDGE aims to deploy innovative helicopter operations making use of high precision navigation. The potential benefits of SBAS (Satellite Based Augmentation System) on helicopters have not yet been unlocked. There are important helicopter operations that could dramatically benefit from SBAS, such as offshore (oil field) operations, mountain rescue or HEMS. The project will significantly help the aviation industry by:
Helicopter operations to offshore oil platforms are limited by the technology available. In bad weather, the flight crew use the weather radar to navigate towards the rig and avoid obstacles. The weather radar is not intended for this purpose and the procedure has high crew workload. SOAP (SBAS offshore approach procedure) is a new type of approach for EGNOS to overcome these problems and meet a significant need in the industry. The new SOAP procedure is less reliant on weather radar, offers highly accurate navigation, lowers crew workload, and allows a cross-check against the existing altimeter source thanks to EGNOS altimeter guidance.
What is PINS?
PINS (Point in space approach) is a helicopter approach procedure for EGNOS recently standardised by the International Civil Aviation Organisaation (ICAO). PINS approaches are designed for airports where conventional navigation is not available, eg to remote mountainous areas or to existing airports to allow an approach from the side of the airport. PINS allow access from any direction. Thus, helicopters can be taken out of the main approach path to the runway at busy airports, so they don't use valuable slots. PINS can also be designed to allow helicopters to avoid noise sensitive areas.
What is APV?
An APV (Approach with Vertical guidance) approach is an SBAS-enabled approach similar to an Instrument Landing System (ILS) approach. It is flown in the same way as an ILS and has similar performance. The lateral accuracy is equivalent to an ILS localiser and the guidance is provided against a geometric path in space. This type of approach is flown to a given Decision Height (DH). The lowest possible DH for APV is 250 ft which is significantly lower than for Non-precision Approaches (NPA).
What is HEMS?
HEMS (Helicopter Emergency Medical Services) are used for the transfer of injured or sick people to hospital. On HEMS missions, helicopters sometimes have to fly under bad meteorological conditions and at any time of the day. Air rescue operators are very interested in using new aiding systems, such as EGNOS which offers a new a rotorcraft-specific steep Instrument Flight Rule (IFR) approach with final segment slopes up to 9°. The use of EGNOS can decrease the risk of accidents and may allow air rescue helicopters to fly in degraded meteorological conditions.