OPTIMAL Deliverable D4.6.2: Test report of EC 135 flights

Abstract

The document describes the results of the EC135 R/C flight trials that have been carried out with DLR’s research helicopter FHS, an EC 135, in Bremen. A curved approach procedure has been developed in WP2.4 for Bremen airport taking into account the idea of simultaneous non-interfering rotorcraft IFR operations. This concept offers the possibility of allowing individual rotorcraft approaches that do not interfere with standard fixed wing traffic and thus will contribute to increase capacity in terms of airport throughput. Since future ATM operations will be based on 4D trajectories, rotorcraft IFR operations might as well require 4D capabilities. A basic requirement for this kind of operation is the rotorcraft’s capability to meet a required time of arrival (RTA) at a given waypoint. The functions developed within OPTIMAL for EC135 experimental Flight Management System allow flying a time referenced curved approach with an RTA given at the Missed Approach Point which has been defined at the end of the curve. These functions and the design of the procedure itself have been tested in flight trials at Bremen airport. The main objectives were to verify the flyability of the curved approach and to assess the 4D capability of the experimental FMS functions. SBAS (EGNOS) has been used as primary input to the navigation system. 35 approaches to Bremen under various weather (wind) conditions have been carried out. The curved approaches have been flown with two different guidance concepts: a tunnel display and a bug-PFD-guidance display. All approaches have been flown manually without any SAS assistance or autopilot assistance. With respect to the Flight Technical Error (FTE), the results obtained with the tunnel display are better than those obtained with the bugs guidance concept. With the tunnel guidance concept, pilot stayed in almost 100% of the flight time from the IF down to the MAPt within the tunnel (tunnel dimensions 80m x 60m). Using the bugs display, pilots deviated in up to 15% of the flight trials more than 40 meters from the nominal flight path. Pilots clearly expressed their preference for the tunnel display. They reported about a by far lower workload compared to the bugs display. With the tunnel display, this rather complex procedure, that includes steep and curved segments in addition to speed reductions during the curve, is flyable without further automation. The tunnel itself provided sufficient situation awareness. In the first 27 approaches, required times of arrival (RTAs) have been given for the MAPt to verify the 4D capability of the FMS. Pilots have been able to achieve this RTA with an accuracy of less than 5 seconds. Basically the trials have shown that • The developed curved approach procedure is flyable • With the tunnel display this rather complex procedure is flyable without further automation and with a sufficient accuracy and an acceptable level of workload. • The tunnel itself provided sufficient situation awareness. • With additional speed guidance information, the procedure can be flown with a very good 4D accuracy (less than 5 seconds).