Helicopter SBAS guidance for IFR steep and curved approaches

Abstract

The Institute of Flight Guidance of the German Aerospace Center (DLR) in Braunschweig is involved in the EU project OPTIMAL. One of the objectives was to demonstrate the rotorcraft system’s 4D flight guidance capabilities. For these advanced interoperability flight trials the FHS (Flying Helicopter Simulator) – the highly modified Eurocopter EC 135 T1 research helicopter from DLR - is equipped with an SBAS receiver and a special 4D-capable experimental rotorcraft flight management system (FMS) using also a 4D referenced flight guidance. SBAS offers a performance comparable to an ILS CAT I without requiring any specific installation on ground and consequently is well adapted to rotorcraft IFR operations at isolated helipads like for example hospitals or helidecks. In the framework of the flight trials the practical flyability of the helicopter-specific steep and curved time referenced IFR approach procedure should be confirmed. The approach procedures were initially developed for Bremen airport (EDDW). Vertical guidance allows a precise height control throughout the final descent and reduces the risk of collision with terrain at night or in bad weather conditions. Approaches with vertical guidance are known as being much safer than laterally guided NPAs referring to worldwide aircraft accident statistics. The paper will provide an analysis of the flight results which promise very good navigation accuracies regarding time-based 4D-curved approaches. The Flight Technical Error (FTE) denotes the ability of the pilot to follow the displayed guidance indications. Furthermore, the paper illustrates the evaluation of SBAS positioning data, the HMI solution based on a head-down primary flight display (PFD) incorporating with a “tunnel-in-the-sky”-style visualization and the Advanced Flight Management System.