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Optimized Procedures and Techniques for IMprovement of Approach and Landing

Final Report Summary - OPTIMAL (Optimized Procedures and Techniques for IMprovement of Approach and Landing)

In order to propose and provide some solutions to answer to the airport capacity and future environmental constraints, OPTIMAL project was launched in 2004 in the Sixth European framework and within ATM2000+ Programmes.

OPTIMAL was an air-ground cooperative project, which was aiming at defining and validating innovative procedures for the approach and landing phases of aircraft and rotorcraft. The objective was to increase airport capacity and to reduce environmental impacts (noise and carbon footprints) while maintaining or even improving operational safety. On the ground system side special attention was placed on the new tools, which were necessary for air traffic controller to efficiently and safely manage the OPTIMAL procedures.

The project's work packages (WPs) were structured as follows:
-WP0: project management and dissemination;
-WP1: operational concept;
-WP2: procedures definition, development and design;
-WPs 3, 4, 5: aircraft; rotorcraft; ground functions developments (respectively);
-WP6: The validation and conclusion;
-WP7: exercise management and support;
-WP8: exploitation, normalisation, standardisation and recommendations.

An important integrated project such as OPTIMAL needed strong validation plans in order to correctly assess the adequacy of the expected main results which address on the one hand the high level ATM objectives regarding capacity, safety, and environmental impacts and on the other hand the feasibility of the advanced procedures.

Two validation techniques were applied in the OPTIMAL validation process:
- Fast time techniques were suitable for a preliminary assessment of the benefits of a new concept in the ATM environment using a mathematical model to provide the results of the simulation and has rules defined to represent the relationship between the different actors of the validation scenario. They consisted in analytical studies applied for safety, environmental and economic assessments and fast time simulation applied for the capacity assessments.
- Real time techniques were characterised by the presence of one or more subject matter expert as controllers or pilots that perform their operational tasks in a realistic real-time environment. Real time techniques are generally used for assessing the human factors aspects, but also to validate the interoperability between systems. In the OPTIMAL validation process, real time simulation and flight trials were applied as real time techniques.

Two types of exercises ensured the consistency of the overall validation process:
- Benefit assessments assessed the benefits obtained from the implementation of the new procedures according to the high-level objectives capacity, environment and safety.
- Feasibility assessments evaluated specific functions for airborne and ground systems and include the validation of flyability requirements, operational requirements (both for pilot and controller), airground interoperability requirements and systems performance requirements.

The continuous descent arrival or approach concept has been studied for a long time and has even been applied in some airports for few years. The international community acknowledges the environmental benefits of CDA in term of noise and gas emissions. The concept studied in OPTIMAL is Advanced CDA in the sense it is not radar vectored but based on RNAV and with use of FMS. The objective is to have repeatable noise friendly operations with higher automation; this is possible thanks to available onboard function like RNAV operations and FMS managed vertical profile, and thanks to improved ATC support tools such as accurate planning and additional monitoring.%lthe OPTIMAL research programme allowed to successfully achieve many experiments and tests which demonstrate the flyablilty of the ACDA procedures and the benefits brought by the ACDA. It allowed also assessing the implementation of ACDA in a busy ATC environment and demonstrated the flyability of future ACDA with high accuracy RTA capability. But several points need to be further studied by future research projects as ERAT, Clean Sky, SESAR.

The ICAO Global Air Navigation Plan for CNS/ATM Systems recognised global navigation satellite system (GNSS) as a key element of communication, navigation, surveillance and air traffic management (CNS/ATM) systems and a foundation upon which states can deliver improved aeronautical navigation services. The GNSS consists of core systems (as GPS, GLONASS and GALILEO in the future) and its augmentation (as GBAS, SBAS, ABAS, GRAS). Existing (GPS & GLONASS) core satellite constellations alone do not meet aviation's strict requirements for precision approaches in terms of integrity, continuity, availability and accuracy values. To meet the operational requirements for various phases of flight, core constellations require augmentation, which can be obtained in different ways:
- ground based augmentation system (GBAS);
- satellite based augmentation system (SBAS);
- aircraft based augmentation system (ABAS).
The GBAS flight trials conducted successfully in OPTIMAL allow to demonstrate the flyability of the GBAS procedure and the very good performance of the GBAS system paving the way for future Cat II/III operations.

The work carried out in OPTIMAL allowed to demonstrate the flyability and the performance of the LPV SBAS procedure in San Sebastian and the tangible operational benefits brought by such a procedure. It is considered that such procedures are particularly suited to regional airlines, general aviation and helicopters in small and difficult airports and could be a back-up for medium and large airports. In Europe, regional airlines have started to show interest in the added-value of EGNOS-based flight operations.

The development conducted in OPTIMAL demonstrated the capability of the ABAS solution to meet APV 1 criteria. The next steps consist now in consolidating the performance, especially in terms of certification, the objective being to demonstrate that the performance achievement guarantee is equivalent to SBAS.

The 'Enhanced Vision System' (EVS) concept developed in the frame of the OPTIMAL project focused on the use of weather penetrating sensor technology and the presentation of the image to the pilot on a head-down display. The recently released final rule (2004) of the FAA for enhanced flight vision systems (EFVS) clearly acknowledges the operational benefits of such a technology but the use is restricted to head up displays and US aircraft operating within national airspace.

The All Weather Operations Steering Group (AWOSG) of the JAA has proposed some amendments towards an international standard acceptable by the ICAO but also with the restriction to head-up display technology.

In the frame of the OPTIMAL project, the main focus has been in enhancing EFVS to head down displays, instead of limiting its use to head-up display systems, as current standardisation efforts seem to aim at. The concept of operation allows the crew to operate an aircraft on an approach procedure in low visibility below the prescribed minima with help of EVS sensor and a head down display.

The feasibility of an EVS head-down procedure was examined that may provide the same operational benefits under low visibility as the FAA rule on enhanced flight visibility that requires the use of a head-up display (HUD). The main element of the described EVS head-down procedure is the crew procedure within cockpit for flying the approach. The task sharing between pilot-flying and pilot-not-flying is arranged such that multiple head-up/head-down transitions can be avoided. The pilot-flying is using the head-down display for acquisition of the necessary visual cues in the EVS image. The pilot not flying is monitoring the instruments and looking for the outside visual cues.

The basic idea of a displaced or dual/displaced threshold is the addition of a second threshold on a long runway at least 1500 m from the original one, so that the displaced glide slope is approximately 260 ft above the other, resulting in a reduced wake vortex landing separation.
The main benefit of dual/displaced thresholds is the reduction of the wake vortex separation between a heavy and a medium from 5 NM to the radar minimum of 2.5 NM, resulting in a higher landing capacity.

Summarising the outcome of the validation activity, the following main conclusions and recommendations have been obtained:
- With DT operation a significant increase of arrival traffic throughput in the simulations could be obtained. With DT applied the arrival throughput is in the order of 45 ARR/h and, in particular, appears to be rather independent of the portion of 'heavy' arrivals. Since without DT operation the throughput was measured as 42 ARR/h for 20 % of 'heavy' and only 40 ARR/H for 40 % of 'heavy' it could be demonstrated that benefit of the DT operation increases with the portion of 'heavy' arrivals.
- Generally, no significant increase in workload has been observed with dual threshold operation compared to the baseline scenario. A slight increase in controller-pilot communication has been measured if no advanced planning support is given to the controller.

Advanced planning support to controllers has no significant influence on the arrivals and does not significantly decrease controller workload. But it has an effect on the departures. It mitigates the departure capacity drop down and increases arrival and departure efficiency and departure predictability.

The area navigation (RNAV) concept is a method of navigation which permits aircraft operation on any desired flight path within the coverage of station-referenced navigation aids or within the limits of the capability of self-contained navigation aids, or a combination of these.

Following these OPTIMAL achievements, some recommendations can be drawn up for the implementation of RNP AR procedures, as indicated below.
- To fully benefit from RNP AR & RNP-xLS operations, the whole 'ATC & aircraft' must be considered.
- Adapted HMI is required for both ATC and airborne in order that the ATC is able to identify clearly RNP AR aircrafts and that the crew can monitor its achieved RNP performance with sufficient alerting mechanisms. Training will be required for both ATC and pilots to carry out RNP AR operations.
- Regarding RNP-xLS procedures, standardisation will be needed regarding the transition between RNP and xLS capture and phraseology.
- Within OPTIMAL project the possibility of applying RNP concepts for ensuring vertical guidance has been considered but the concept of vertical RNP needs to be further studied and standardised.

Within OPTIMAL, specific rotorcraft procedures were studied taking into account steep glide slope procedures and curved/segmented approaches. The procedures developed were tailored in order to allow simultaneous non interference (SNI) IFR flights of rotorcraft with the aim of not affecting aircraft operations.

The OPTIMAL research program allowed to successfully achieve many experiments and tests which demonstrate the flyablilty, the benefits and the integration in ATM of the rotorcraft specific procedures studied (steep, curved, LPV, SNI). These rotorcraft specific procedures are key enabler for improving rotorcraft integration at airports as:
- they provide a cleaner environment thanks to noise footprint reduction;
- they increase airport capacity (passenger throughput);
- they improve safety thanks to vertical guidance.
This is achievable using:
- steep & curved procedures using GBAS or SBAS guidance;
- independent rotorcraft and aircraft traffic flows (SNI).

Within OPTIMAL, some specific ground functions and ATC tools were developed in order to support the procedures described in the previous paragraphs with the following objectives:
- better support the procedures developed in OPTIMAL;
- reduce the air traffic controller workload;
- improve the overall safety level.

Assessing the project results as a whole, the following conclusions can be drawn:
-all main activities in terms of studies, developments and tests defined in the initial contract were carried out in the frame of the project, albeit with a slight delay;
- all project objectives were met and OPTIMAL demonstrated that the studied procedures provide in general the expected benefits in terms of capacity, safety and/or environmental impact and that the procedures are feasible;
- the OPTIMAL results were disseminated during the whole duration of the project, especially through the successful final user forum in June 2008..
- all OPTIMAL partners acknowledge the very good and fruitful cooperation within the consortium and the management team thanks the 24 partners for their involvement and their cooperative spirit to meet the project objectives;
- to conclude, the OPTIMAL project delivered some validated, innovative concepts and promising results, which will certainly contribute to the SESAR JU and the implementation of the future European ATM system.

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