First DREAMS project flight trial at Twente airfield brings Enhanced Arrival Procedures supported by advanced GNSS into the operational environment

The Twente demonstrations saw NLR’s research Cessna Citation II join a Lufthansa A319 and a TUI fly B737 Max 8 to evaluate under real visual conditions, using the Indra Navia GBAS ground station, the runway dual markings and dual precision approach path indicator (PAPI) needed for Second Runway Aiming Point (SRAP) and IGS (Increased Glide Slope)-to-SRAP approaches.

The trials, which will be evaluating visual aspects, flyability and gathering performance data, are part of the SESAR Very Large Demonstration (VLD1) DREAMS project, which aims to evaluate whether a series of new Enhanced Arrival Procedures (EAP) will bring benefits in terms of noise and optimisation of wake separation, as well as reduced flight time or runway occupancy time for certain runway configurations. The project gathers nine partners under coordination by Indra: two ANSPs (DFS, ENAV), two aircraft manufacturers (Airbus, Dassault), one aircraft system manufacturer (HONEYWELL), two research organisations (NLR, DLR), and EUROCONTROL. In addition, airspace users (Lufthansa, TUI Fly) are also participating under contractual arrangements.

Overall, DREAMS aims to increase operational efficiency, shorten flying times and lower emissions by bringing EAP supported by advanced GNSS navigation technologies closer to industrialisation.

The trials are testing the following EAP:

• Dual final approach slope, one being steeper, namely ISGS (Increased Second Glide Slope);
• Dual thresholds to single runway, namely SRAP (Second Runway Aiming Point);
• A combination of the two: IGS-to-SRAP (Increased Glide Slope to Second Runway Aiming Point);
• Operation of GBAS GAST C in CAT II conditions.

EUROCONTROL has a multiple role, leading the work programme on SRAP & IGS-to-SRAP demonstration at Twente, specifically contributing to the demo on GBAS GAST-D performance analysis using our own latest generation Multi Mode Receiver (MMR); leading the DEMO Plan deliverable; and leading the task on standardisation and regulatory framework evolution.

The SESAR VLD1 DREAMS project is a continuation of the work undertaken under two other SESAR projects related to airport capacity (PJ.02) and integrated CNS (PJ.14), both with strong involvement of EUROCONTROL.

Demo #1

Twente SRAP & IGS-to-SRAP (October ‘21), with NLR test aircraft with full GAST D capability using the Indra Navia ground station, TUI Fly B737 Max8 and Lufthansa A319, using interoperable GBAS GAST C avionics.

Demo #2

Frankfurt ISGS (December ‘21 to May ‘22) with Lufthansa commercial aircraft (A320 family) using GBAS GAST C, in conditions down to CAT II. Objective is to gain experience with GLS CAT II operations in an ATC environment. A prototype GAST-D ground station is also installed at Frankfurt and has been used for preliminary tests with the EUROCONTROL MMR in preparation of Demo #1.

Demo #3

Roma Ciampino ISGS (November ‘21 to March ‘22), with Dassault Falcon & Honeywell Embraer 170 test aircraft and using RNP SBAS approaches with steeper glide slopes (3.9° and 4.4°).

Demo #4

Twente ISGS (February to June ‘22), with NLR test aircraft and using RNP SBAS with 3.5, 4.0 and 4.49° slope angles, with the objective to assess the dual PAPI solution, serving the conventional and increased glide slope.

The demonstrations at Twente, a non-commercial airfield, took place during the first week of October with the goal of evaluating in real visual conditions the runway dual markings and dual PAPI as necessary for SRAP and IGS-to-SRAP approaches, in line with the PJ.02 solution requirements. The prep work had been done earlier in 2021 within PJ02 when EUROCONTROL and Lufthansa Aviation Training used an A319 simulator at Frankfurt with airline pilots to run three flight simulation campaigns on approach procedures in different visibility and weather conditions including SRAP, ISGS and IGS-to-SRAP.

The existing runway markings on Twente’s Runway 05 were expanded for Demo #1 with a second (ICAO compliant) set of markings, consisting of a second threshold, touchdown and aiming point markings, located 1,020 metres further, together with a second PAPI on the opposite side of the runway. The approach trials were based on GBAS GAST-D temporary ground station, supporting different GLS published approaches with 3.0, 3.2, 3.5, 4.0 and 4.49 degrees glideslope.

The NLR test aircraft (a Cessna Citation II) was equipped with two GAST-D receivers and made a large number of approaches (8 days with 6–20 approaches per day) for data acquisition and pilot evaluation purposes. A different guest pilot each day was asked to fly the approaches.

The Lufthansa and TUI fly aircraft evaluated visual aspects, flyability and gathered performance data on the 3.0 and 3.5° approaches to both thresholds.

The preparation of the demonstration also provided valuable insight into regulatory aspects, such as the GBAS frequency allocation process, approval aspects of the systems and planned flight operations, as well as the necessary infrastructure preparations. The findings will feed into both the regulatory work package and the next trials.

Second Runway Aiming Point (SRAP)

SRAP is a published approach procedure, consisting, when active, in approaching and landing on a published second runway threshold and aiming points located further on a runway, in simultaneous operations to conventional threshold. The two final approach segments to each aiming point are parallel. Landing further down from original aiming point allows shifting the noise footprint in final approach towards the airport area, optimisation of wake separation, and runway occupancy time for certain runway configuration, resulting in increased operational efficiency and reduction of flying time and emissions. The SRAP procedure can be supported by satellite-based navigation: GBAS and SBAS.

Increased Glide Slope to Second Runway Aiming Point (IGS-to-SRAP) operation is considered as a variant type of SRAP operation, combining an increased glideslope onto the second runway aiming point. Compared to SRAP, this enables not only to increase further the noise benefits (but also the possible runway throughput gains with further reduction of wake turbulence separation minima), as a function of the glideslope angle (and of the distance between the conventional landing threshold and the second one). The maximum slope angle is 4.49°, excluding steep approach operations.

Since the validation of GAST D SARPS (enabling CAT II and III operations with GBAS) a new generation of MMR’s has reached maturity and is now available, incorporating for instance the full set of authentication requirements.

EUROCONTROL has acquired a Collins GLU-2100 model, with GAST D software load in trials at Twente airport, and which was installed onboard the NLR test aircraft. In addition, the flight inspection system aboard the aircraft also was equipped with a GAST D receiver. Indra Navia provides a fully GAST D compatible, portable GBAS ground station for the Twente trials.

VLD 1 tests allow the comparison of the function and performance of this new MMR generation, with the ground recordings against the SARPS and MOPS requirements, and building a baseline for later interoperability tests with ground stations of other manufacturers, as was done for GAST C.In parallel, DFS is certifying its GAST C ground station at Frankfurt airport to permit CAT II operation and has enabled its GAST D station there for preliminary static testing with the EUROCONTROL MMR.