The German Aerospace Centre (DLR) has successfully demonstrated manually flown, satellite navigation-guided precision approaches designed specifically for helicopters. When the equipment - categorised experimental at present - is approved, helicopters arriving at airports will be able to use curved or steep approaches that keep them well clear of fixed-wing traffic, delivering them direct to the helicopter landing site, the DLR reported to the 16-18 September Royal Aeronatical Society European Rotorcraft Forum in Liverpool, UK.
The project, known as OPTIMAL (optimised procedures and techniques for improving approach and landing), set out to define and validate four-dimensional (4D - the fourth dimension is time) helicopter approach procedures, using satellite navigation with a space-based augmentation system - in this case the European Geostationary Navigation Overlay System (EGNOS). Flying trials at Bremen airport, Germany using the DLR's Eurocopter EC135, the test team developed what it calls simultaneous non-interfering (SNI) procedures which offer the opportunity to provide additional aircraft movements at an airport by separating rotary-wing precision approaches completely from those for fixed wing.
The same technology could bring precision guidance to noise abatement patterns and Instrument flight rules approaches for urban heliports, and can be used for en-route navigation.
The DLR says its trials have demonstrated the "flyability" of the helicopter approach procedure under simulated instrument flight rules conditions. The agency says the pilots reported no problems using the system, the most successful version of which employs a primary flight display with marked "tunnels in the sky" along which which the pilots flew the aircraft.
The navigation receiver used is a GARMIN GNS 480 which provided data to the helicopter's flight management system (FMS). It had been modified by the manufacturer to receive and process EGNOS MT0/2 signals, despite the fact that these are not certificated yet for safety critical purposes, points out the DLR. The FMS's software was extended to provide 4D navigation by displaying required times of arrival (RTA) at waypoints and landing.
During earlier DLR flight tests the system's en-route capability had been demonstrated over a 56km (30nm) route flight containing 15 waypoints. It was flown manually, reports the agency, and there was RTA error of only 3s at the destination, with the aircraft remaining throughout within the pre-set parameters, tracking within 25m (82ft) vertically and 10m horizontally of its ideal path.
- Read Learmount's blog about flying approaches
Source: Flight International
